I have tried four times to get a replacement o-ring to seal on the oil cooler adaptor. Each time, the o-ring seals fine when the car is first started cold (high oil pressure) & then fails & begins leaking after the engine warms up. I have tried the stock GM replacement o-ring & the thicker type recommended by the GSCA. I have tried using silicone or fuel lube in the groove to hold the ring in place & I am torquing the nut to 40 lbft. Each time, the o-ring ends up looking very tattered, & in one case actually broke in two. Can anyone explain what I am doing wrong? Also, what is wrong with just eliminating the oil cooler since I am running a large remote System-1 filter mounted in a cool place behind the right headlight? System-1 claims this fined aluminum filter housing will drop oil system temperature 10F. How much does the radiator cooler (cooled with 100F+ water) drop the oil temp?
An adaptation of prior suggestions:
It has been previously suggested to use the square o-ring out of an oil filter. However, these are a little wide to fit in the indentation in the oil cooler adaptor.
I solved this by pulling the o-ring out of the old filter and taking it over to my bench grinder.
I stretched it out a little to get a straight surface and ran the outer surface lightly against the grinding wheel. Continued working it around until the entire outer surface was ground down enough to fit the adaptor indentation nicely.
Since the adaptor seals against the block exactly like an oil filter normally would, this works great.
The square rubber o-ring in most oil filters also seems to resist twisting and tearing like a normal o-ring. Guess it should - oil filters have been designed to seal good for ages.
Just be sure to wipe a little oil on whatever seal you use before tightening - a dry seal can become a useless piece of rubber otherwise.
Rubber has a lot of friction unless oiled first.
David Workman
Lake Worth, FL
1987 Grand National (Dark Side)
Wife - 1987 White Turbo T-Type (Princess Leia Side)
OK, I finally got the oil cooler adaptor to seal on the fifth try. Apparently overtorque, as mentioned in some of the replies was my problem. I was torquing to 40lbft, which crushed the o-ring. 25lbft worked. The problem is that nowhere on the website or in the service manual is this adaptor or its correct torque value even mentioned. I used a Viton size #144 o-ring of 70 durometer rating which I obtained for $2.50 at the local rubber supply store. This is same as the GM replacement except it is 60 durometer rated which means slighty less hardness & durability. The secret is - don't overtorque it!