I've had a pesky oil pan leak since I've owned my 88LT, it's in pieces for paint and to fix all those little things including the leaky oil pan. What sealer(s) have you used with the best results? Thanks.


Chris
88 K100LT
Springdale, Arkansas USA

I am a big fan of Hylomar.
Years ago, I was using Loctite products too.
Oil pans are not under pressure and unless the pan is warped, there is a good chance that the oil leak comes from somewhere else (oil pump, oil pressure sensor,....) and is sprayed by the wind pressure.
If I recall correctly, there are O rings between the engine block and the pan. These O rings must be replaced. I believe they are the orange one resisting to high temperature.

I agree that Hylomar works wonders, and Permatex make an assortment of decent sealants too. I really like this stuff...Drei Bond Silikon 1209 is my choice. It's almost clear, and an anaerobic sealer (doesn't harden in the absence of air), so it stays pliable and rarely do I have to re-seal anything. I even use it on the base of my Airhead's cylinders where no gasket seals the two machined surfaces and major torquing action exists.
Here's an image with the BMW part number too.

Thanks for the replies. I used black RTV on the pan when I first bought the machine in 2008, sealed ok for a while then started leaking again.

This whole project started as an air filter check, bottom right faring was off, then the left, then broken upper faring bracket was found, then wind shield was off, broken faring mount found and holy cow it's in pieces! It's 1 of 40 88Lts that came in Tobacco Brown and the 50 liter top case, I think The brown is an awful color so I've wanted to repaint since I bought it. Seems like a good time, I'll try to post some photos in the Renovation section as I move along.

Chris

Chris, take note of what Bert and TWB have suggested, but you also need to be very sure that the sealing surfaces are not marked or damaged in any way whick may compromise the sealing.
If any small burrs are discovered, be very careful in removing them, taking care not to scratch the surfaces. Also, be certain the sealing surfaces are absilutely clean and dry prior to applying the sealant. Any good quality RTV silicone is ok, though the up-market ones tend to be safer in regard to the inner bead not breaking away (sealant inside the engine cavity), which is not too big a deal as there is a pre-strainer on the oil pump pick-up.
Lastly, the oil pump, if it is to be re-fitted to the front of the engine, is a full oil pressure (up to 5 Bar) seal, so a very good sealant is required. I once had to make 3 attempts to get a perfect seal, the oil will be felt leaking by inserting your little finger into the hole where the oil pressure sender wire comes out. BMW recommend 3BOND 1209 for this joint, I use Loctite Master Gasket 515 after first treating with Loctite Primer T, then do not touch the surfaces.
Hope this helps, Dennis

Hmmm, the light just came on - TWB shows a pic of DREI BOND, DREI being German for THREE (3), hence my reference to the product 3Bond (Google it). Not cheap, but very good I'm told, as it is a very high shear strength silicone based sealant, exactly what is required for the high pressure seal between the oil pump housing and engine block.

On a slightly different note if I may, some klutz overtightened a bolt on my
85 k's oil filter cover (one of three bolts) and I er I mean he has slightly stripped the thread on the oil pan itself.
So far it appears that he/I may have gotten enough torque to get a seal (after 200k's no leak) but I just know it won't be long.
Has anyone had any success with helicoil replacement threads? It has been suggested to me to take the oil pan off and re-thread the hole. I'm inclined to wait till it leaks, too tight to waste the oil so soon after changing.
FYG 6nm is not much more than finger tight NOT 2 twists less than 12nm (the lowest mark on my massive torque wrench.)
Back in my box now
Regards all RT

Helicoil-brand and other steel thread inserts are ideal. I recommend them. Once I questioned a helicopter mechanic friend of mine about the use of inserts in aluminium until he kindly reminded me (like I was stupid) that nearly every single fastener in a helicopter's airframe is a steel insert into aluminium. I was humbled.

A Helicoil in a stripped K bike oil pan or oil filter housing thread, if the threads can't just be 'chased' with a tap (but be careful not to take too much metal out), is the way to go. The bolt is a 6mm x 1.0 pitch and needs just 7NM or 5 ft/lbs of torque to be sufficiently tightened.

Before playing with helicoils, I would try to chase the thread with a 1/4" fine thread tape (28 threads per inch).
1/4" is 6.35mm and 28 threads is the equivalent of a .907mm pitch.
It should be strong enough to accept 5 ft/lbs torque.

Thread chasers are always a good first option and Helicoils a good repair as the above gentlmen have stated, and they certainly do hold up to use in alloy as I once had to use them in light armoured vehicles.
I was just wondering has anyone ever made a gasket using gasket paper and had any success I know you would still put a smear of sealant on each side but, just thought.

BIG D

I make paper and/or cork gaskets for sealing quite often, but never for this bike, so far. I should think that a decent enough grade of pliable sealant like as previously suggested would suffice for any of the machined mating surfaces on the engine where a gasket isn't specified. One of my older Airhead boxers had a chronic oil pan leak that was remedied using a thicker than the stock 'paper' gasket and two good beads of sealant. It was caused by a poorly machined surface, ie, a terrible over the 'bars prang scuffed up by the road surface damaged the engine case enough to not allow a good seal to the new deep sump. It worked a charm and only took me a few months to get right back on.

Hmmm, I don't think the paper gasket idea is the way to go in this application, mainly due the spacing of the (3) holes and the fact that they are lugs external to the round cover casting, so there is the possibility of distortion between the bolts. VW (Type 1) engines use paper to sandwich the oil strainer, but they use 6 x M6 bolts, not 3.
If you are really desperate for a quick stripped M6 repair, you could tap the hole out to 1/4" UNC, which is 6.5mm. You will need to drill the cover hole to accomodate the slightly larger bolt. Not pretty, but a solution.
Personally, I would by an M6 Re-coil set, they are excellent in alloy, standard fitment to many machines these days, affectionately known as case savers.

Thanks everyone, all bases covered now, still hasn't leaked but I'll be doing 300k s tomorrow un accompanied so perfect setup for disaster.
HA I laugh in the face of it since owning this bike. It's the first time in my life that I feel I can fix something with all your help.
Cheers RT