hey guys im trying to do some preventive maintenance on my 93 k1100lt and i noticed BMW wants $75 for a thermostat.

does anyone have a quality substitute for the oem part? thanks

What maintenance do you want to do to a thermostat?  If it works then there's no point in replacing it and they seldom fail on K bikes.

I would not mess with it.  It has a rubber sealing ring that you can mess up if you remove the thermostat.

duck wrote:I would not mess with it.

+1 Flush the coolant system then replace the coolant with the appropriate ratio of coolant to distilled water.

Getting that seal in if you remove the thermostat is a real PITA. Been there... Don't worry about it. The thermostat is one of the most reliable parts on the bike.

Ok Ill leave it alone. New to the bike but when I test rode it the fan kicked on around 3/4 way up and sounded fine. It was almost 100F out that day.

Here's how the K1100 cooling system works:



The fan coming on is a good sign. Some bikes that live in cooler climates or sit for a long time will never have the fan come on and the fan seizes from lack of use.  PITA to replace.

A flush of the system of my bike is probably a good move.  Should that be done with the thermostat in place?

brickrider2 wrote:A flush of the system of my bike is probably a good move.  Should that be done with the thermostat in place?

Yes and also when it is open.

Goodluck flushing a cooling system with a thermostat in it. If you removed it then ran the bike it will keep the coolant circulating. As soon as you introduce fresh cold coolant the thermostat will close and keep coolant from flowing.

Remember the job of the thermostat is to maintain a minimum temperature

NoSprk wrote:Remember the job of the thermostat is to maintain a minimum temperature

The job of the thermostat is to maintain an optimal running temperature—not a minimum temperature. If a minimum temperature is wanted, don't install a thermostat, but that won't help engine performance.

The engine is warmed up before each flushing to allow complete circulation and warmed up after the final filling so the thermostat will open, air can be evacuated and the system can be topped up.

Not true. If you didn't have a thermostat your engin would never warm up in cold weather. Even when it's hot out the thermostat keeps the engine temp at a minimum. The engine cooling is what keeps the temp from overheating

Even if it's 100dg outside the constant flow of the coolant and driving on the highway will not maintain a minimum temp the engine needs to run properly. that's why the thermostat shuts till the coolant is past the desired temp. Engine oil won't get up to temp. The cooling fan is there to cool the coolant in the radiator then it cycles

There is a difference between the meanings of optimal and minimum that is eluding you. The thermostat and fan keep engine temperature within an optimal range.