ron mcatee

If we're talking about the internal thermostat located on top of the engine, I suggest a new one if the old one is bad. If it's the thermostat on the inside of the external housing in the right rear fender well that lets oil to the right front fender front oil cooler, it can be rebuilt. I haven't done the latter, but much more knowledgeable guys than me can offer suggestions. I do know that removing the cap and lines can be difficult if they are corroded. I had external thermosta repaired by a local shop who guaranteed the job and would fix any damage they inflicted on it, plus fixing the original problem. I know there couls be a problem with cross threading that cap when you put it back on. You need to be sure which one you are wanting info on. There may be some info on the Pelican site, specifically for your problem.

glenncof

David,

I have not done it yet but sounds straight forward. Internal thermostat is located front-right top of engine. Remove air filter box and MAF sensor. Remove Oil Pressure Switch , required for clearance. Looks like two nuts hold it in place. Fits only one way. New O-ring required, put oil on it for good seal & avoid install damage. I found new Behr (oem ?) with o-ring <$100 with free shipping.

Today I put meat thermometer next to temp sensor held with duct tape. I was able to get temp meter (in dash) just below the 90C mark by letting it idle after warm-up. Meat thermometer never got above 130F. Jumped on the highway and it dropped to mid point between two lower marks (90C & 60C, so ~75C)on meter. Search this forum for Jack Olsen comments/picutres/diagram.

Also oil filter was hot and front cooler was cold. External thermostat (fed from sump by scavenge pump) directs oil either to oil filter or front cooler. So that does not look like an issue here.

So I have concluded the internal thermostat is not closing all the way. This would be consistent with extended time to get up to temperature during idle and the drop in temperature at street/highway speed where air cooling is coming into play.

Or at least that's what I am thinking !

BMWDavid

Glenncof,

That does not sound to bad about channging out the internal thermostat. Though I'm still not sure if I have a problem yet.

Now that the temp is up in the 40's I see an oil temp reading of about 165*-175* (about halfway between bottom white block and first white line) after 20 mins of rural highway driving. The temp will rise just a bit if I get into stop and go driving and come back down as I get back on the open road.

The oil filter is quite warm and the oil lines in the right rear wheel well are warm before the external thermostat. The lines forward of thermostat are cold.

How does that sound?

David

glenncof

David,

I just checked ALLDATA at my local library. It's a professional repair data base.

It says the thermostat is to open at 80C. This would be 2/3rd up between the 60C and 90C marks.

Half way would be 75C. 6% difference is not much given the likely inaccuracies involved.

I think pulling it out and testing in hot water is the only way I'll know. Arrr..

Two things got me on to this. MPG has been off lately by >5% lately in cold weather (running 20W50) and I suspected some problems with thermo in summer but running hot. BTW, I did have a overheating problem in traffic 12 years ago (55K miles, now at 176K) resolved by replacing internal thermo according to mechanic. I verified it by the p/n on work order but looking at flow diagram I don't see how it could have been the likely issue (more likely External Thermostat).

Mike Murphy

It turns out that I do not have a thermostat problem at all. The reality of it all, is that we have air-cooled engines. These air-cooled engines operate at a temperature the correlates to the outside temperature. Ever notice how when it's really hot outside, people complain about hot engine temperatures? I didn't realize that when cold outside, these air-cooled engines also run cold. 80C is about 176F, and that is completely normal for my engine. I too, have a perceived loss in fuel economy. I also run my headlights, driving lights, heaters (3 blowers), fresh air blower, and sometimes defrosters in the winter time, so this could have an effect on fuel economy as well.

Just my $0.02, but you might not have a thermostat problem.