I am going to be replacing the oil cooler o-ring on my wife's 99 Prelude BM, this was the cause of an oil leak that has been gradually getting worse.

My question is can coolant leak into the engine through the oil cooler? Because after me being deployed for 3 months the car has had a rash of problems kick up. Here's some info:

- Engine coolant wont stay filled. No visible leaks.

- CEL threw codes 71,72,73 (Misfires in cylinders 1,2,3)

- Removed Valve Cover to find coolant mixed with oil all over the valve cover (just on the valve cover, not lots, but no coolant is good) I couldnt see coolant anywhere else. Diptick does not have any signs of coolant.

- Spark Plugs are clean

My guess is i have to replace the head gasket... but the only thing that i dont understand is when i start the car, it has a rough idle, then is steadys itself and it runs perfect... That's why i dont think it's the head gasket. If there is a chance that coolant can get into the engine through the Oil Cooler that may be a possible cause. Any input? Maybe i'm missing something.

I just want to beat this car already. It has been a monster of problems since we bought it. Thanks in advance for any information fellas.

 

"My question is can coolant leak into the engine through the oil cooler?"

I am wondering this also. i am throwing no CELs and i'm not losing coolant but i am getting some oil in my coolant reservoir gradually. i don't see coolant mixing in oil when i change it but when i took the oil cap off i started to see some of that famous coolant/oil mix on the top of the cap (very very little but enough to worry me)

I was fine until one day i installed a sandwich plate at the oil cooler/filter. Since then i took it out but same issue.

Thinking maybe when tightening everything to make sure it wouldn't leak i did it too tight and maybe the oil cooler o-ring could be to blame?

any insight from someone who had similar issue would be greatly appreciated.

 

to add some info:



Leaky Oil Cooler - Coolant shows traces of oil. Transmission or engine damage can result from the mixing of coolant with transmission fluid or engine
http://www.arrowheadradiator.com/Rad...20Failures.asp

 

Well if the coolant was entering through the oil cooler it wouldn't affect the combustion chamber therefore it wouldn't cause misfire codes. Two things you could do: pressurize the cooling system. Look for leaks. If it looses pressure and the level decreases without seeing anything you have a problem somewhere. Next do a leakdown to further narrow the problem.

Also how does the coolant look ? Are you sure its not moisture in the oil ?
What color is the smoke out the back of the car ? What does it smell like ?