Leak at the oil cooler thermostat

Post by **erikv11** » 07 Sep 2012, 00:57

After a couple weeks of work I've now got a replacement engine (stock) into my 95 R, and it starts up and seems to run well. Lifters have quieted down.

But before I take it out of the garage I want to fix the oil leak I saw at startup: right where the thermostat connects to the block, somewhere on the left (firewall) side, there is a steady drip-drip-drip that increases with throttle. It is just a very slow ooze at idle.

I am virtually certain it is not the oil pan seam, which is freshly done with Volvo pink stuff. I did the pan o-rings while the engine was out. The oil leak definitely comes from behind the oil cooler thermostat, which is lower than that seam line by a hair. The seam itself doesn't get wet. Whew. Yes I know it can be tricky; I have removed the thermo twice, to reseat the square o-ring gasket, but at removal the gasket appears to have been straight (not crushed anywhere) and reseating hasn't helped. Mating surfaces seem mighty clean and undamaged. The thermo I picked up from a mechanic I trust, he said the thermo, the gasket and the oil lines were only very lightly used (and the lines look brand new).

I'm going to hopefully pick up a new gasket today if the dealer here in DC (Don Beyer) has one, but otherwise any suggestions for when I get back home and go after this on Saturday? Would it be wise and effective (or stupid) to try sealing around the o-ring with RTV black?

Maybe I need to swap in one of the 175k thermostats I have lying around, I suppose the surface could be crooked or something.

850_GLT_Owner · Post by **850_GLT_Owner** » 07 Sep 2012, 10:48

I had a hell of a hard time putting that rectangle gasket in due to those notches that make it less than rectangular on the thermostat. I used some silicone gasket sealer to help hold it in place during re installation. I struggled hard putting it in correctly, but once the silicone gasket helped hold the rectangle gasket in place, it made things far easier.

Post by **erikv11** » 07 Sep 2012, 13:40

Thanks, I have already used a little dab of RTV to hold the ring in place, I am pretty confident it is sitting in the grooves. It leaks specifically from the same place every time, that area I described toward the passenger side of the thermostat.

Post by **confused_al** » 07 Sep 2012, 19:28

erikv11 wrote:...right where the thermostat connects to the block, somewhere on the left (firewall) side, there is a steady drip-drip-drip that increases with throttle.

I had some kind of leak there, just opposite side. I believe it is because I tightened one side first then the other, that caused a little gap on leaking side. The leak stopped after I re-tightened the two bolts alternately to make sure the oil t-stat is evenly pressed onto the block.
BTW, a good torx bit will make this easier.

Post by **erikv11** » 09 Sep 2012, 01:38

Thanks al, I gave that a try but no go.

So I removed the thermostat completely and checked it with a straight edge - it is bent in two different places, they totally explain the location of the leak.

I'll try to straighten it tomorrow, if that doesn't work then I'll put the old one back in.

Post by **erikv11** » 09 Sep 2012, 13:58

So I straightened it with narrow wood blocks, a 3 lb hammer and the hard, flat surface of a table saw. It isn't as flat as the old one I compared it to but is WAY closer, I installed it and looks like it will not leak. I'll keep an eye on it.

Lesson learned (again): for aluminum (thermostat) to aluminum (oil pan), snug up first, then tighten, no need to overdo it.

Post by **jblackburn** » 09 Sep 2012, 17:36

erikv11 wrote:So I straightened it with narrow wood blocks, a 3 lb hammer and the hard, flat surface of a table saw. It isn't as flat as the old one I compared it to but is WAY closer, I installed it and looks like it will not leak. I'll keep an eye on it.

Lesson learned (again): for aluminum (thermostat) to aluminum (oil pan), snug up first, then tighten, no need to overdo it.

Didnt know your own strength, eh? Thats the same reason I don't like to have people change my oil other than me - even on my new car under warranty. Some mechanic stripped out the drain plug on my Honda so much that I had to keep using oversized oil plugs each time.

Post by **Ozark Lee** » 09 Sep 2012, 20:16

I have screwed with trying to use the new O Ring / Gasket on a couple of them and at the end of the day I just clean up the old ones and use them over rather than fight with trying to get the replacement to fit long enough for me to get the bolts on.

...Lee.