Newly purchased 12/1986 K100RT overheating indication problem

michaelvass

michaelvass

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Number of posts : 58

This is my first topic after just doing an Introduction. I am in Brisbane, Australia and just bought this 12/1986 K100RT with only 18,500 km and looking really nice. Here is a pic of the bike so we know what we are talking about (getting new tyres, its the best pic I have at the moment). It my first bike in over 30 years since I was into motocross as a kid, so enjoying riding again and glad I discovered these old Beemers, seem like great bikes.

Newly purchased 12/1986 K100RT overheating indication problem 20170414

I suspect this is more an overheating indication problem rather than an actual overheating problem.

Whats happening is that after about 5-10 minutes idling after a cold start (or about 15-20 minutes riding) the fan + overheat light will both come on at exactly the same time. Weird as the manual says fan is supposed to come on at 103C and the light at 111C. The fan runs great when working, so no problems there (I know there are issues with fans not working). The fan + overheat light will then stay on for extended periods, way beyond what normal fan cooling of the system should take care of. When and if this stops, they will both stop/go out at exactly the same time again. This cycle continually repeats itself. On my last ride the fan + light was even coming on when I was doing 100 kmh plus on a flat open road.

I don't think the coolant is actually boiling and the bike does not seem to be all that hot, so I am guessing this is false sensing and an electrical issue.

In the last 2 months since I've owned the bike I've done a bit of research online and done the following, but still can't solve the issue...

1. Thought it might be a clogged radiator/engine so ran 2 cycles of distilled water/flush through the system for about 400 km, then installed Nulon Blue Coolant:Distilled Water at 40:60. Strange thing is that for some reason the bike actually behaved normally (in my limited experience) while the flush was in the system ie. the fan + light stopped coming on all the time but instead once the bike was actually hot and needed cooling the fan came on before the overheat light, done what seemed a normal cooling job for a few minutes and prevented the overheat light from coming on at all, and then turned off. However when I drained the flush and put in the fresh coolant mix, it immediately went back to the old problem of the light + fan constantly coming on. Could it be that the high concentration of pure water in the flush let it cool more efficiently or let the sensor do its job better?

2. For some reason the the bike had no thermostat fitted when I purchased it, maybe it was a previous owner's idea of attempting to fix this problem. I fitted a new thermostat at the same time I put in the fresh coolant mix (ie. after the flush treatment). The thermostat I used is a Tridon TT214-180 which I have read on the forums is suitable for these bikes. The overheating indication issues were there since I purchased the bike, so they occurred both with no thermostat and then later with the new thermostat.

3. I also thought it might be the radiator cap, so installed a new BMW cap at the same time I put in the flush treatment. Like I said, the bike behaved normally when the flush was in the system so I initially thought the new radiator cap solved the problem. But then when I put in the new coolant and it started misbehaving again I eliminated this as the cause.

4. Now I am thinking it could be the Coolant Temp Sensor. I have an aftermarket one on order from here (http://sartnas.com/forum.php?mod=viewthread&tid=21833&extra=page%3D1) so will test it once it arrives. I also have found a graph on the forums to measure resistance versus water temperature of the sensor, so will do this test on the old sensor on the stove-top after I replace it, just to see if it was indeed faulty.

5. If the new Coolant Temp sensor does not work, then my manual tells me the other things I could look at are the Temp Sensing Switch/relay or the Water Pump itself, although it does not elaborate on how exactly to test these things.

MartinW, the guy I purchased it from done a pretty good job of getting it on the road after sitting in storage for 12 years or something, and replaced the fuel pump & internals/lines etc. I saw the bill, cost about $600 in BMW OEM parts. I've also been running Techron in it for the past couple of tanks like you suggest.

Charlie99, can you please elaborate on the simple checks you suggest?

Hopefully somebody is familiar with this problem and can help me with a quick fix, thanks.

92KK 84WW Olaf

92KK 84WW Olaf

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We will find you lots of non OEM parts that do the job just as well so stay close to the forum.

You ticked off a lot of boxes on the fan but from what you say there does seem to be an electrical issue. The fan sensor only works when bike gets to temperature after the thermostat has opened so you have effectively found that sensor and fan are working. It also tells you the thermostat is opening [or not present as it was when you got the bike].

Did you have a look at the earth connections under the tank? There is a cluster on the centre tube and they should be leaned up electrically.

You have 2 sensors on the cooling system, one is for the fan and the other feeds into the ICU and warning light.

I suspect it is the second one is your issue since the fan is coming on and working ok. This other one is located behind the radiator and a little tricky to get at but 88 informs me it can be done.

However if sitting for 12 years don't dismiss the possibility of the water pump impeller being corroded reducing water circulation very significantly.

Holister

Holister

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I doubt very much it has anything to do with the coolant/thermostat/cap. And I suspect that testing the sensor output as outlined in the trouble shooting page you'll find on the Portal tab, will tell you that its OK.

The temp sensor you havre on order has 2 sensors in it. Both are earthed thru the threaded body. There are 2 connections in the EV1 type socket on the sensor. One goes to the FICU which will use that to adjust mixture at startup. The other connection goes to the temp controller which will switch the fan and the temp warning light. As you say, the fan and warning light should come on separately at different temps. My guess is that the temp controller is Kaput or there's some dodgy wiring.

As Olaf says, Check your earth connection as well.

td5

td5

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My friends 94 K75 did the same thing, the bike was sitting for years and he got it with 18,000Kms on it. After a good service etc, when we rode out the temp light would come on but not the fan, and just for fun intermittantly. The bike did not get hot as the temp gauge was still in the normal, in the end it turned out to be the relay. I do remember the relays are not cheap so perhaps someone has a spare?

92KK 84WW Olaf

92KK 84WW Olaf

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One thing after sitting for years is that electrical connections may have degraded and on occasion instead of a component being kaput its the electrical connections are not passing current correctly. Earths, connections etc can do this.

Its worth meeting up too and sometimes swapping out a component can sort the connections or identify it's not the culprit.

Might be able to swap a relay with someone.

But do things one at a time so if something does not work out all you have to do is go back one step.

I had a spare FICU unit here and wasn't quite sure how it was so it went into the K last week. It's now given about 400 miles without any issues. I want to use it to test out Magda's [JediGirl] K100 when we are next back at it. Can be as easy as spending time with meters etc when we have the bike apart. Her water pump is at 88s house awaiting some parts.

robmack

robmack

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The tests to perform are detailed in this IBMWR article:

http://www.ibmwr.org/ktech/fan-diagnosis.shtml

Perform these tests before you start replacing parts. The parts replacement route will be expensive; the diagnosis route will be educational.

My question to you is "Has a previous owner fooled with the wiring harness sometime in the history of the bike?"

The only way the fan and overtemp light could come on simultaneously is because the sensor in the stand pipe is going to ground potential, and overshooting the intermediate resistance values that tells the overtemp relay when the coolant is hot enough to require the fan and when it is too hot. There could be several causes:
- broken temp sensor
- wiring shorting to ground (i.e. burnt insulation)
- defective relay or relay socket

It is possible that the soldering within the over temperature relay itself is dodgy. After performing the above tests and confirming proper operation of the sensor, the thing I'd do next is open the temp relay and carefully examine the soldering connections on the printed circuit card, and especially those around the external connector. They may have cracked due to vibration over time. The solder at the joint will look mirror-like and uniform if it is good; greyish and clumpy if the joint is cold. You might even notice small fractures.
Newly purchased 12/1986 K100RT overheating indication problem Tools_Header_Joints

Newly purchased 12/1986 K100RT overheating indication problem Tools_Header_Joints

Fixing them is real easy. Just use a soldering iron to reheat and reflow the solder where ever it looks like a cold joint. Using liquid flux will help a great deal to reflow the joint. This will correct the problem if due to fatigue cracking. I've breathed new life into a couple K100 relays this way.

MartinW

MartinW

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OEM fans were not the best and most Brick riders eventually replace them with an aftermarket fan. OEM fans unless exercised regularly seized up due to being subjected to water and road scum. Spal seems to be a popular replacement choice. I've been running a Davies Craig with a fully sealed motor for the last 18 years never missed a beat. To fit the DC required cutting off the OEM motor support arms. aligning the DC shroud with the OEM shroud and cutting off the surplus outer. I made up four "U" clips and used them to attach the DC to the OEM with pop rivets. I also swapped the DC blades for the OEM ones .At the time of fitting a also fitted an override switch.
Regards Martin.

IainM

IainM

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Number of posts : 12

I have recently fixed a very similar issue with my '86 RS with replacement of the temperature sensor behind the radiator. This was after cleaning and flushing the rad, checking the stat and cleaning grounds under the tank and on the gearbox. The resistance settings for the sensor at the temperature relay contact didn't appear to be wildly out either, c/w the response graph vs temperature, and I was convinced that the sensor was OK.

It was frustrating me so I ended up buying a new sensor and a s/h relay from Motorworks - my issue was solved with the sensor replacement and I now have a spare relay (although I did read this rarely fails).

It is odd that, for you, the light and the fan come on at exactly the same time and you could use a potentiometer to mimic the sensor operation if you are confident to do it. This is was my next step before I lost patience and decided to throw some parts at it instead.

Iain

michaelvass

michaelvass

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Thanks everybody for your replies, some ideas and things to check I will do so as soon as I get a chance - I am away from the bike for the next 10 days or so.

Nobody so far has come up with any suggestions why the system was behaving normally when I had the radiator flush treatment in it, but returned to abnormal once I put new coolant into it.

I have a new temp sensor coming in the mail, so I guess my first step will be to put that in, check the earth connections as well, and see what happens. If that fails, move on to checking the temp control relay.

What's the best way to remove the temp sensor? It says on the IBMWR article that you need to remove either the airbox or the radiator - which would be easiest? I've removed the air intake pipe and can get my hand in there and touch the sensor, but I haven't had a go at taking the clip off yet. I can see how its tricky because I think you need to unclick it simultaneously at the top and bottom of the connector, right? Can it be done this way as a shortcut without removing the airbox or radiator?

IainM - You had a similar problem to mine, but your light & fan were not coming on at the same time. What exactly what were they doing?
robmack- Thanks for the suggestion about checking the solder connections on the temp control relay, I'll definitely be taking a look at them.

Last edited by michaelvass on Tue Jul 04, 2017 4:17 pm; edited 1 time in total

michaelvass

michaelvass

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92KK 84WW Olaf wrote:
Did you have a look at the earth connections under the tank? There is a cluster on the centre tube and they should be leaned up electrically.

Olaf, what do you mean by "leaned up electrically"?

michaelvass

michaelvass

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Number of posts : 58

Holister wrote:My guess is that the temp controller is Kaput or there's some dodgy wiring.
As Olaf says, Check your earth connection as well.

Holister, by temp controller, I assume you are talking about the temp control relay/sensing switch/temperature switch in the control box under the fuel tank (its named 3 different things in the 3 manuals I have access to).
Is there any way to test this? The Haynes manual says it can only be tested by substitution. Does anybody know where I can buy an aftermarket one, or a reasonably priced Bosch one?
If anybody in Brisbane is keen for a drive to Mt Tamborine where I live and let me do a swap test, I will shout them lunch & a beer.

Newly purchased 12/1986 K100RT overheating indication problem Pictur10

92KK 84WW Olaf

92KK 84WW Olaf

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I priced that unit at Motobins recently, was £28 plus VAT excluding mailing. UK VAT is 20%. Not sure what happens VAT for mailing down under.

Laitch

Laitch

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michaelvass wrote:Nobody so far has come up with any suggestions why the system was behaving normally when I had the radiator flush treatment in it, but returned to abnormal once I put new coolant into it.

I have a new temp sensor coming in the mail, so I guess my first step will be to put that in, check the earth connections as well, and see what happens. If that fails, move on to checking the temp control relay.
Can it be done this way as a shortcut without removing the airbox or radiator?

Let me be the first to suggest that the "normal" behavior was coincidence. The explanation involves the ratio of coolant, the type of coolant, the amount of coolant, the presence of air pockets, rapid overheating caused by low coolant volume/restriction, and who-knows-what-else but is beyond my poor powers of description right now. Laughing

You are one of the few new brick owners I haven't heard grumble about the coolant changing procedure and that has me believing you haven't used enough coolant nor purged air from the system sufficiently. If you're using a 60% distilled water/40% coolant mixture, have purged the air from the system intermittently while filling the system and have the overflow reservoir reading just below max on a cold engine, you should be good to go. Maybe the remedy does involve more replacement parts but I'm not getting that impression from what you've described.

By "leaning" I think Olaf meant cleaning the grounds to bare metal and tightening them but only he knows for sure. Laughing

Last edited by Laitch on Wed Jul 05, 2017 1:46 am; edited 1 time in total

92KK 84WW Olaf

92KK 84WW Olaf

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its Kleaning I meant!

Diddle I say that? Just as Laitch says, cleaning up the earths.

Laitch

Laitch

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92KK 84WW Olaf wrote:

its Kleaning I meant!

That's what I meant, too! Spellchecker fails again. Newly purchased 12/1986 K100RT overheating indication problem 177381

MartinW

MartinW

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https://www.aliexpress.com/item/High-Quality-Engine-Coolant-Temperature-Temp-Sensor-For-BMW-Motorcycles-K-100-K-75-K75-K100/32680512124.html?Ali Express cheap coolant sensor $10.92 US shipped.
Regards Martin.

Holister

Holister

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michaelvass wrote:

Holister wrote:My guess is that the temp controller is Kaput or there's some dodgy wiring.
As Olaf says, Check your earth connection as well.

Holister, by temp controller, I assume you are talking about the temp control relay/sensing switch/temperature switch in the control box under the fuel tank (its named 3 different things in the 3 manuals I have access to).
Is there any way to test this? The Haynes manual says it can only be tested by substitution. Does anybody know where I can buy an aftermarket one, or a reasonably priced Bosch one?
If anybody in Brisbane is keen for a drive to Mt Tamborine where I live and let me do a swap test, I will shout them lunch & a beer.

Correct Michael.
Robmack suggested above to give the internals (particularly the soldered pin connection inside) a visual inspection. Dry solders will be noticable but fine cracks in the solder joints not so. Use a lens/loupe/magnifying glass and good light to check from all angles.

Did you test the temp sensor. Easy to do instead of wasting money on buy parts that may not be needed.
Pull the plug off the FICU under the seat and measure the Ωvalue when cold and when at operating temp on pins #10 and #13 counting from the cable end including black spaces. Should be 2.5kΩ @20ºc and around >300Ω @80ºc.

What's the best way to remove the temp sensor

Lower fairings will need to be removed in any case. I think just easing the radiator out a little would be the easiest.

Worth checking the wiring in case its been bodged.... which would be my first guess.

TacKler

TacKler

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Michael,

I have a couple of weeks holiday from Saturday so can assist if required. It will be a break from house painting, gardening, etc.
I would suggest draining the system into a clean container, so you can reuse it. That way you can remove the radiator, have a look at the fan/motor and will have good access to the sensor. Removing the lowers on an RT fairing is no big deal. It makes things so much easier and less stressful.

I'll bring a spare temp relay for you to use as well. Might throw in some DeoxIT as well (Correct spelling Mr. Blakey?).

PM me and we can work out a date.

Dave.

michaelvass

michaelvass

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Thanks Holister. No, I haven't had a chance to test the temp sensor yet because I am overseas for the next 10 days or so, but will test it just like you say when I get back. I went ahead and ordered a new temp sensor last week because its a likely culprit and I found a cheap aftermarket one online. IanM also said earlier that he had a similar problem to mine which was fixed by a new temp sensor, even though the old one seemed okay when he tested it. At least when I put the new one in I can eliminate this as the cause.

With regards the pins, I'm a bit confused. Here is a pic of the FICU pins I found online. I assume this is looking head on at the control unit box, so the cable end of the plug would be on the right hand side, right? This would mean counting the pins on the plug from opposite the cable end, wouldn't it? ie. On the plug they would be the 1st & 4th pins closest to the cable.

Newly purchased 12/1986 K100RT overheating indication problem Efi-co10

Last edited by michaelvass on Wed Jul 05, 2017 6:32 am; edited 1 time in total

michaelvass

michaelvass

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TacKler wrote:Michael,
I have a couple of weeks holiday from Saturday so can assist if required. It will be a break from house painting, gardening, etc.

Gday Dave, that sounds great, much appreciated Newly purchased 12/1986 K100RT overheating indication problem 212902

I'm not back home until mid next week, so anytime after should be okay. I already have the fairings off since doing the coolant change etc last week. The new temp sensor that I ordered should have arrived by then, so before you come I'll first see if that works. If still no good, sounds like my next step would be to check the relay. Will let you know how it goes. Sounds like I have to remove the radiator, or at least loosen it and pull it back, to get at the temp sensor.

How did you end up with a spare temp relay? Is it normal to carry this as a spare, or did you have previous problems as well? Just curious.

By the way, are you good at removing the mirrors on these bikes? I've tried the thumping with your hand method to no avail and don't want to break it.

michaelvass

michaelvass

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MartinW wrote:https://www.aliexpress.com/item/High-Quality-Engine-Coolant-Temperature-Temp-Sensor-For-BMW-Motorcycles-K-100-K-75-K75-K100/32680512124.html?Ali Express cheap coolant sensor $10.92 US shipped.
Regards Martin.

Thanks Martin, that's the same temp sensor that I have already ordered online. Now just need to find a source for the temp relay in case I need a new one after doing some further testing.

Holister

Holister

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michaelvass wrote:Thanks Holister. No, I haven't had a chance to test the temp sensor yet because I am overseas for the next 10 days or so, but will test it just like you say when I get back. I went ahead and ordered a new temp sensor last week because its a likely culprit and I found a cheap aftermarket one online. IanM also said earlier that he had a similar problem to mine which was fixed by a new temp sensor, even though the old one seemed okay when he tested it. At least when I put the new one in I can eliminate this as the cause. Yes but he also said that yours was different in that both fan and warning light come on together.

With regards the pins, I'm a bit confused. Here is a pic of the FICU pins I found online. I assume this is looking head on at the control unit box, so the cable end of the plug would be on the right hand side, right? This would mean counting the pins on the plug from opposite the cable end, wouldn't it? ie. On the plug they would be the 1st & 4th pins closest to the cable.

No. That pin-out is for the plug. The reference in that diagram to 'Bert 2009' is our illustrious leader and founder of this forum, Crazy Frog. He has also put together a very comprehensive section with everything you need to know about troubleshooting just about anything that can go wrong with our beloved K100. The 'Troubleshooting' link is on the Portal Tab. You'll find instructions on testing at the FICU plug about 3/4 the way down. This page is a MUST READ. Heed the warnings in the yellow blocks.
Newly purchased 12/1986 K100RT overheating indication problem Test-FI%201

Newly purchased 12/1986 K100RT overheating indication problem Test-FI%201

MartinW

MartinW

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Michael the OEM relay is a bit pricey between $80.00 to $100.00 Au. I have wondered if there is a generic relay that could be substituted. One of the resident electrical Gurus might have a better idea.
Regards Martin.

92KK 84WW Olaf

92KK 84WW Olaf

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I could be wrong but suspect a faulty relay might cause a fan to come on unnecessarily or delay/prevent it coming on. But I don't think it will affect the temperature warning light.?

Both fan and warning coming on together seem to point toward the sensor unless the wires from the sensor are somehow damaged and both going to earth at the same time....? But sensor would seem to be where to start.

michaelvass

michaelvass

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Laitch wrote:You are one of the few new brick owners I haven't heard grumble about the coolant changing procedure and that has me believing you haven't used enough coolant nor purged air from the system sufficiently. If you're using a 60% distilled water/40% coolant mixture, have purged the air from the system intermittently while filling the system and have the overflow reservoir reading just below max on a cold engine, you should be good to go. Maybe the remedy does involve more replacement parts but I'm not getting that impression from what you've described.

Gday Laitch, I'm an Aussie, we don't grumble Very Happy

I know where you are coming from with the idea of insufficient coolant or air in the system. I researched everything online I could find and read the manuals numerous times before changing the coolant on my bike, so was aware it could be the cause of my overheating problems and made sure it was done right. This was pretty much my bible http://bmwmotorcycletech.info/k-coolant.htm. But like I said earlier, the coolant is not overheating in my opinion, seems to be more of an indication problem.

After running the flush for 400 km (during which the system behaved "normally") I had my cousin come over with his back flush tool and we gave the whole cooling system a good 'ol back flush, as a clogged radiator was the first thing we suspected. He used to have his own radiator repair shop so was clued up and assisted in putting in the new coolant, making sure it was to max capacity, no air bubbles, reservoir to correct level etc. He actually owned a brand new K100RT just like mine back in the 1980's when they were the ducks nuts, so has a bit of previous K-bike experience.

I also rechecked the water level at the radiator cap a couple of times after going on rides, and it remained full to the brim. I'm convinced the system is filled correctly, but I have been wrong before.

For people who may have had overheating problems before due to insufficient coolant or air in the system, did you also experience the light and fan coming on/off at exactly the same times? If there were no issues electrically, and the bike was overheating because of insufficient coolant, I would assume the fan would still come on first at 103C and then the warning light at 111C.

michaelvass

michaelvass

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Holister, thanks for clearing up that the diagram was for the plug, not the unit itself. All makes sense now.

I assume this is the page you are referring to?
http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/bike-wont-start1.htm

This diagram, also on that page, is why I thought the layout was for the control unit. By the why, it's wrong isn't it? As you said, the water temp sensor goes to #10 and #11 is empty, right?

Newly purchased 12/1986 K100RT overheating indication problem Captur10

Holister

Holister

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Correct link.

eeerr... yeeaah! that diagram doesn't look correct.... disregard that diagram. Refer to the first one you posted and the table of tests beneath it in the Troubleshooting page. Looks like Bert's been into the single malt again.

Laitch

Laitch

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michaelvass wrote:
. . . I'm an Aussie, we don't grumble

I think I see the problem. You haven't been reading this forum. Laughing

robmack

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Holister wrote:Correct link.

eeerr... yeeaah! that diagram doesn't look correct.... disregard that diagram. Refer to the first one you posted and the table of tests beneath it in the Troubleshooting page. Looks like Bert's been into the single malt again.

That diagram comes out of one of the Bosch technical manuals for the Jetronic. The Jetronic was used on many vehicles and it might reflect the correct wiring for an automotive use of the Jetronic, but it is incorrect for the K-bike. The previously posted diagram is correct.

92KK 84WW Olaf

92KK 84WW Olaf

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Holister wrote:Correct link.

eeerr... yeeaah! that diagram doesn't look correct.... disregard that diagram. Refer to the first one you posted and the table of tests beneath it in the Troubleshooting page. Looks like Bert's been into the single malt again.

The Eccentrics are working on this particular little software glitch. Its caused by the visual screen and the visual receptors being out of sync with each other.

It's taking time but we believe it will eventually be cured with a stopover between Canada and France, somewhere in the land of Eccentrics.

We believe we have traced a particular malt manufactured here that will solve that particular issue. Thing is that it doesn't work as a virtual cure, it has to be hard copy.

robmack

robmack

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michaelvass wrote:What's the best way to remove the temp sensor? It says on the IBMWR article that you need to remove either the airbox or the radiator - which would be easiest? I've removed the air intake pipe and can get my hand in there and touch the sensor, but I haven't had a go at taking the clip off yet. I can see how its tricky because I think you need to unclick it simultaneously at the top and bottom of the connector, right? Can it be done this way as a shortcut without removing the airbox or radiator?

It is possible to remove the clip holding the harness lead onto the sensor body from the front without removing the radiator or airbox. However, it will not be possible to remove the sensor from the standpipe like that. I think the easiest of the two choices is to remove the airbox rather than the radiator. It ends up being a bit more fiddly working with the tools inside the space but still doable. I personally find removing and replacing the rad a PITA. DAMHIK.

IainM

IainM

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michaelvass wrote:
IainM - You had a similar problem to mine, but your light & fan were not coming on at the same time. What exactly what were they doing?

From a cold start on my daily commute, the fan would come on after 20mins followed about 5 minutes later by the temperature overheat indicator - just as they would with a genuine overheating problem. But the rad hoses were not that hot to touch and so I doubted the engine was actually overheating.
Iain

Rick G

Rick G

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Like most modern engines the K100 has a bypass for the coolant so the coolant can flow while the engine heats up quickly and evenly.
This is achieved but having 2 valves in the thermostat housing which opens the bypass when cold and as the temperature goes up the thermostat slowly opens which directs the coolant through the radiator and closes off the bypass.
Without the thermostat the majority of coolant goes via the bypass which has no cooling effect. So if you have the incorrect or no thermostat the engine will most likely run hot but the main hoses that you will feel could quite likely feel cool.
Make absolutely sure that you have the correct thermostat in it.

michaelvass

michaelvass

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RicK G wrote:Make absolutely sure that you have the correct thermostat in it.

Yeah, good point. The Thermostat I put in is a Tridon brand TT214-180 readily available in Oz which I chose after reading this forum http://www.motobrick.com/index.php?topic=4903.0
Is anybody else also using this and can confirm it is suitable? If not, which aftermarket one is recommended? - The BMW OEM is, as usual, very expensive.

Newly purchased 12/1986 K100RT overheating indication problem 110

I also purchased the matching gasket, a Tridon TTG47 (as recommended on that forum) but when I went to put the thermostat into the bike it would not fit with the gasket on it. It fitted perfectly with the gasket removed, so I installed the thermostat without any gasket, assuming that's how it was designed to be. Now you have got me thinking. Have I got the wrong thermostat &/or gasket? Is there a way to fit it with the gasket attached? Could this be the cause of my problems?

Newly purchased 12/1986 K100RT overheating indication problem 210

The thermostat went in as per this diagram easily with no gasket, but with the gasket on it would not even fit through the entry hole. So if I have the right thermostat and gasket, beats me how you get it to fit in.

michaelvass

michaelvass

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robmack wrote:It is possible to remove the clip holding the harness lead onto the sensor body from the front without removing the radiator or airbox. However, it will not be possible to remove the sensor from the standpipe like that. I think the easiest of the two choices is to remove the airbox rather than the radiator. It ends up being a bit more fiddly working with the tools inside the space but still doable. I personally find removing and replacing the rad a PITA. DAMHIK.

So you cannot remove the sensor even if you have a long extension to your socket wrench? I'm away from my bike at the moment so can't check, but I thought this would have been possible. What's the reason why not, the angle of it?

robmack

robmack

Life time member

Number of posts : 2334

Michael,

Here is a picture of that area of the engine with the radiator removed.

Newly purchased 12/1986 K100RT overheating indication problem 2013-017

Newly purchased 12/1986 K100RT overheating indication problem 2013-017

You can imagine that with the airbox removed, access to the sensor it restricted by the bypass pipe. That pipe can be removed from the T-junction on the stand pipe on the left, allowing it to be moved slightly out of the way. That will allow more access to the sensor hex fastener. Once that sensor is loosened, it can be removed by hand from the front between the radiator and engine block. Doable but fiddly.

michaelvass

michaelvass

Silver member

Number of posts : 58

ok thanks Robmack

michaelvass

michaelvass

Silver member

Number of posts : 58

A couple of postings back I talked about the Tridon TT214-180 thermostat I bought and how it does not fit my K100RT with the gasket on it, only without the gasket.

Like I said, I bought this because it was recommended here http://www.motobrick.com/index.php/topic,4903.msg30742.html#msg30742

HOWEVER, I have just read this http://www.motobrick.com/index.php/topic,7603.0.html where it states that the aftermarket thermostats which are 35 mm (such as my Tridon) might not allow enough water through to the pump. So I am really wondering if I have been led a bum steer by that first article and bought the wrong one, and this is what is causing my overheating problems.

So sorry to ask again, but can you guys please tell me what aftermarket thermostats you use in your bikes. Or should I just get the BMW thermostat?

michaelvass

michaelvass

Silver member

Number of posts : 58

I just found this post...
https://www.k100-forum.com/t7589-thermostat-gasket
...where Charlie99 says he got the Tridon TT214-180 thermostat to fit when using a TTG26 gasket instead of the TTG47 which I purchased. That post is from 2014 and I'm not sure if he is still an active member of these forums, but I've sent him a PM asking to confirm if all is still good with this combination. Can anybody else confirm?

I'm still a bit concerned with what is said in this post about 35 mm thermostats not letting enough water to the pump...
http://www.motobrick.com/index.php/topic,7603.msg54213.html#msg54213

charlie99

charlie99

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Number of posts : 11701

I think the motobrick post is referring mainly to the distance of the closure of the bypass port ...from the movement of the thermostat itself at temperature

if you follow my post you may notice that I gained some distance , by um "peening" the rear end of the thermocouple connection to the rear block off by about 5 mm ..or so

the seal around the thermostat , I predict is quite important , in as much as the bypass temps , and the cooled radiator water temps cannot be isolated ...over heated bypass coolant could well be unregulated on its way back to the pump

I believe that rt - lt versions are the most noticed "hot machines" of our marque ... whilst in cooler climes this is an advantage ..but in hot climates ...a real pain in the upper legs etc .

just to add some clarity perhaps ?

TacKler

TacKler

Life time member

Number of posts : 1345

michaelvass wrote:
How did you end up with a spare temp relay? Is it normal to carry this as a spare, or did you have previous problems as well? Just curious.

By the way, are you good at removing the mirrors on these bikes? I've tried the thumping with your hand method to no avail and don't want to break it.

Michael,

I have a spare parts bike with a complete set of relays. I can take it out and bring it along. I don't have a spare sensor though. Also I've not experienced the problems you speak of (yet).

I can practice thumping on a spare set of RT mirrors I have, to see what the best practice is to remove them. I can understand you not wanting to damage the paint on your fairing. Others may have a better idea.

Oh, and just be wary of the dreaded K pox. You will end up with a garage full of K bikes before you know it.

indian036

indian036

Life time member

Number of posts : 1458

TacKler wrote:Oh, and just be wary of the dreaded K pox. You will end up with a garage full of K bikes before you know it.

Fake News! I only have 6, with thoughts of a 7th.

(By the way, how many bikes owned confirms a diagnosis of K pox?)

Bill

robmack

robmack

Life time member

Number of posts : 2334

One is enough to expose the victim to the K-pox bacterium, symptoms of the disease only appearing later, far too late for any treatment. There is no known antidote nor no known cure once this insidious affliction has taken hold. The K-pox has been known to invade dreams, and result in the victim frequently attending BMW hookups, boot sales and flea markets searching for new acquisitions of the marque or parts for the current collection. Gastly!

michaelvass

michaelvass

Silver member

Number of posts : 58

Dave, do you have a spare thermostat you can bring for testing as well? If so, is it a BMW OEM one? I am liking the idea that the Tridon TT214-180 thermostat I fitted with no gasket could be the cause of my problems. I will buy, fit & test a TTG26 gasket instead of that TTG 47 that couldn't fit, see if that does the trick.
Thinking back about my prior actions, I put the new Tridon thermostat into the bike after I done a radiator flush a few weeks ago and that's when the overheating light + fan problems really started getting bad. Could the thermostat be the problem then? Highly likely I say.
As I wrote earlier, before this there was no thermostat fitted. The warning light + fan problem did occur from date of purchase 3 months ago, but not to the degree since putting in the thermostat. I do remember when draining the system to do the flush that the coolant level as filled by PO was a little low, so that could explaIn the initial overheating issue (he purchased it at an auction last December after it sat in storage for many years to get roadworthy and resell. He done a full service but never took it on the road, so he wouldn't have had a chance to see the overheating issue). During the the 400 km of flush treatment the bike ran "normal", probably because I corrected the coolant level to where it should be. But when I drained the flush, put in new coolant and the Tridon thermostat, that's when the problem came back, worse than before.
It still could be a Temp Sensor &/or Temp relay fault, but eliminating the thermostat as the cause will be the first step, once I get back home next week.
Regards the K-pox, that would explain why I mysteriously found myself looking at K bikes on bikesales.com.au last week. 3 months ago I didn't even know what a K bike was! Now I find myself a junior K bike mechanic & auto electrician.
Nobody has replied to confirm what, if any, aftermarket thermostats they are using. Are we still using the original 30 year old BMW ones then?

Laitch

Laitch

Life time member

Number of posts : 3253

robmack wrote:One is enough to expose the victim to the K-pox bacterium, symptoms of the disease only appearing later, far too late for any treatment. There is no known antidote nor no known cure once this insidious affliction has taken hold.

Destitution has been suggested as an effective temporary control. Smile

robmack

robmack

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Number of posts : 2334

charlie99

charlie99

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Number of posts : 11701

I have a spare thermostat here (original type ) but you will still need a new oring around it

I have seen a few radiators with issues , like silicon sealant remains , all in the input side of the radiator , from past works I guess ...

could this be a contributing factor ?

but you need to get the thermostat working correctly in the first place

I wonder if an oil pump seal job has been done and the impeller is not fitted correctly ?

or the fluid filler cap seal is incorrectly fitted - missing the second seal (quite common issue resulting in fluid escaping as it heats )

give me a message if you want to borrow - whatever a thermostat

Rick G

Rick G

admin

Number of posts : 12055

Compare the length cold of the thermostats they should be the same. For many years I searched for a thermostat that was the correct length but never found one. Some were within 3mm but not the same and Tridon didn't have one listed for the early Ks

blaKey

blaKey

Life time member

Number of posts : 2756

Aftermarket thermostat: Tridon High Flow TT2014-180
gasket: Tridon TTG26

Charlie99 (Charlie) provided us with photos of a modified thermostat (can't find the photos...do a search?) which I did to my thermostat and the bike (1986 RS) is running fine!

blaKey

blaKey

Life time member

Number of posts : 2756

Found it!

Have a look here...page 14, post 671. This is the mod as mentioned above.

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