Coolant in the oil but zero symptoms of a bad head gasket

Hello I have an 08 tundra sr5 5.7 that I’m having troubles with. Getting a lot of coolant in the oil but zero symptoms of a bad head gasket. No exhaust smell or smoke, good compression on all cylinders, no misfires or anything but just coolant in the oil but nothing in radiator that I can tell. I’m wondering if the oil cooler on these can fail and send coolant in the oil. The radiator goes down quite quickly, it’s basically being dumped in the oil. I’ve ran compression on all cylinders warm and hot and have close to the same readings on compression gauge but I’m at a loss here and I really would appreciate any help here. Oil cooler appears to have been leaking oil, the ac compressor is covered in oil

 

Welcome

 

Thank you sir. I got a feeling I’m gonna be on here a lot lol

 

Yes, try pulling the coolant lines out of the oil cooler, couple them together, then pressure test the cooling system.

 

Sorry to hear about your trouble. Any oil in the coolant? Checking the oil cooler sounds like a good idea.

 

Yes a lot of coolant in the oil unfortunately and alright, I will try to couple the lines together and pressure test it tomorrow. I appreciate all help on this.

 

Mileage on the truck?

 

They most definitely are. I have a complete gasket set just in case but definitely am not looking forward to it if that’s the problem. And it has 300,000 on her but the motor has been pulled once so really unsure of miles. Bought the truck at auction a few years ago and only now just having any kind of problem and I service it regularly

 

If it is indeed the oil cooler should I replace it or could I leave the lines coupled together and bypass it? Also is it the cooler that fails or the gaskets behind the cooler going onto the block?

 

Depending on the condition of the truck, if I had to do head gaskets and wasn't sure on mileage other than quite a few I'd go all in on a rebuild. Just can't see having to turn around and do a rear main seal or something soon after. Plus that the bearing lubrication went South already. Might have a cracked head. Just have to hope it's the oil cooler, if not, lots of wrenching ahead. Good luck!!

 

If it is the oil cooler is it the cooler itself that went bad or the gaskets that are behind it that went out that allowed for cross contamination?

 

Could be either, it depends on the design of the gasket and failure mode. Typically an oil cooler is a stack of metal plates (copper, stainless steel, aluminum) brazed together (copper, nickel) and sometimes heat cycles or corrosion can break those joints allowing cross talk of the fluids. You should also be able to pressure test the cooler itself if you can find appropriate fittings to block off all the ports but 1 and apply air to it while dunking it in a water tank while looking for bubbles. Caution, sometimes it takes heat to expand the cracks enough to leak, while air does a good job at finding smaller leaks it may also require an extended dunk in "hot" water to get the entire stack to expand similar to how it would with hot engine oil and coolant flowing through it.

Failure of the gasket with cross talking leak paths should be visible when removed.

Either way running a cooling system pressure test as is, then again with the cooler bypass would tell you if that's the cross talk location first. Then removing it to find the failure mode.

 

I appreciate it very much. I will pressure test it both ways and see what she does. Thank you