: Oil in coolant tank

03-20-10, 12:28 AM
:annoyed: My babys been acting crazy lately. Engine on 2000 deville overheating every now and than especially when iI go up big hills. Got a coolant flush with Dex-Cool, prblem still continues I would say about once every week or so. Still drives like a dream but i discovered oil in my coolant tank when engine was hot (Engine Hot-AC Off). I am now pretty certain I need a head gasket and thread job. Can you guys please give me a few tips or maybe recommend North* mechanics in my area (N.J./N.Y.) also funds are limited and can not do right away but looking to do b4 the summer gets here. Is it ok to drive short distances?, my job is only 5 miles away. I am a 80/20 city/hwy driver avg 13 miles/gal. Thanks in advance guys

03-20-10, 10:34 AM
If you've got oil in the coolant I'd say you're in for more than an HG job. That's a very very rare scenario.
By design the N* will almost never mix oil and coolant. That would have to be a very specific and unlikely HG failure.

03-20-10, 12:13 PM
Oil in the coolant leads me to believe you have a leak in the oil cooler coil down in the radiator side tank. Picture a coiled oil line running down through the side tank surrounded by coolant. Oil pressure is much greater than the cooling system pressure so oil flows from the oil line leak point into the coolant side tank. Thus oil in your coolant. Keep in mind that the other side has a trans cooler line so it could be trans fluid as well. In either case it would be wise to change the radiator soon. When you shut the car off, oil pressure drops to zero immediately, but cooling system pressure remains until the engine cools down. IF the leak is sufficient enough, that cooling system pressure can reverse the flow and pass coolant to the oil or trans fluid and coolant does not play well with either. The cooling system can tolerate oil or trans fluid in it MUCH better than the engine or trans can tolerate coolant.

03-21-10, 08:59 PM
You know, I never think of that. I guess I've never had a radiator with internal leaks so I forget that can happen.

Good call. But yes, coolant, even a little in a lubricated environment like the engine or trans is highly detrimental.

03-21-10, 09:44 PM
Still, he is overheating once a week. A little oil or tranny fluid in the coolant wouldn't make it do that.

03-21-10, 10:29 PM
Good point. He did said "Engine on 2000 deville overheating every now and than especially when I go up big hills". That is not a good sign. Get a block test done to check for exhaust gases in the coolant. Buy it from Napa or rent it from Autozone or have it done.

04-10-10, 12:01 PM
I really appreciate the info guys,I really do. Ranger I think you hit it on the nose with the radiator coolant line leak. About a week ago I discovered a leak coming out of the right side cooler line. I just put a new radiator in today and I will be looking for signs of temp rising. I am sure if I continue to overheat I will need hg job done soon thermostat & water pump ok. Other than that my baby still runs great I guess it just has it's moods when she overheats once every week. Well I wll be seein you all in the near future.