head gasket ?

[baybronco]

hey eveyone
i bought a 1998 grand cherokee with 175000 miles on it. it seems to have oil in the radiator but no coolant in the oil. any one have any suggestions of what the problem could be. it ran and drove fine untill a slight over heat. it is a 5.2 v8

thanks all

 

[MudderChuck]

I sure don't know for sure, but if it is leaking through one of the oiling passages (that oil the crank, cam and lifters) it is under pressure, likely higher than the 16 PSI the cooling system normally holds.
If the coolant is leaking into an oil return passage (no pressure) is usually when you see coolant in the crankcase oil or the typical milkshake looking foam on the dipstick.

 

[hogseye]

I would think if it was the head gasket, it would still lead coolant back into the oil, once the engine was shut off and the oil pressure went to 0. The coolant would still be under pressure until the engine cooled down. But on the other hand I cannot for the life of me think of any way the oil could get in the coolant without it being a head gasket!! Will have to think on that one for a little while.

 

[hogseye]

2nd thought. I would drain and flush the radiator and cooling system. If by change someone mixed different types of antifreeze in the radiator, I have seen it react by turning a black oily looking mixture. If you clean it out and it does not reappear then I would not worry about it as long as you keep check on your dipstick as Mudderchuck said. Watch to see if it continues to get "oil" in the coolant. If it does then you need to check deeper.

 

[baybronco]

thanks guys
after further inspection the coolant appears to have gear oil in it.well at least it smells like gear oil. would love to hear any suggestion. do you think if the auto trans fluid was getting in there it would smell like gear oil? also the ABS light is on and has been since i bought it.

 

[MudderChuck]

Is it possible it's water pump lubricant? Has your water pump been changed lately. Old school mechanics most always added a small can of water pump lubricant after changing out a water pump.
Some radiator sealer is also black.
Just some thoughts.
The oil system has a check valve in the bottom, so the oil doesn't run back into the crankcase. If the lifter isn't being worked it's doubtful it would pass much oil (or coolant). The oil pressure may be zero, but you may not pass very much coolant into the pump side of the oiling system before the radiator cools back down. After the cooling system (and motor) cools down, the cooling system actually goes into vacume.

 

[SteelHeadz]

If your trans. cooler is modular with the radiator, check the trans. fluid for contamination of coolant. It's possible that the leak is occuring within the radiator and not in the engine. A good verification test to try would be to use a radiator combustion tester. This will determine if there is the presence of combustion gasses in the cooling system. A simple pressure test should yield a leak into the radiator's transmission cooler tank and should show the presence of coolant with the ATF.