Help in diagnosing coolant/oil mingling
Question:
>At first, I noticed that there was oil in my coolant recovery tank, but >there was no sign of coolant in the oil. Now that’s changed and the oil >has taken on that *milky* look on the inside of the filler cap. I’m >assuming that there’s a gasket leak allowing the oil and coolant to >intermingle (I don’t want to entertain the idea of a block or head crack).
If you have oil in the coolant, but no coolant in the oil, you don’t have a blown head gasket or a cracked head. In order for oil to get into the coolant it had to come from somplace that has oil at a higher pressure than the cooling system. for example, the only oil in a cylinder head of the V-6’s is drip fed oil that comes up through the pushrods and drips off the rocker arms to lube the valve stems. On the other hand if you had a crack in an oil galley, you would have direct access to oil at 40-60 p.s.i. More than enough to overcome the mere 16-18 p.s.i. in the cooing system. Another thing to check is the condition of the transmission fluid. If the truck has an automatic transmission, there is a cooler in the tank of the radiator. If this cooler leaks, it is also under higher pressure than the radiator…most of the time. If you turn the truck off when it’s hot, you might get a backflow of the coolant oil mix into the transmission. Then things could get *really* expensive. Good luck, Big Daddy ICQ#6342575 ASE Master Auto Technition Chevrolet Certified Master Tech.
Response:
At first, I noticed that there was oil in my coolant recovery tank, but there was no sign of coolant in the oil. Now that’s changed and the oil has taken on that *milky* look on the inside of the filler cap. I’m assuming that there’s a gasket leak allowing the oil and coolant to intermingle (I don’t want to entertain the idea of a block or head crack). My question: Is there any way to figure out which head gasket is leaking other than removing the heads and visually inspecting? BTW, the vehicle is a 1991 GMC Jimmy 4×4 with the 4.3L V6. If anybody can help, I’d really appreciate it. Thanks Fred
Response:
Coolant/oil can be a bad head gasket, or a warped head (which can cause the bad gasket). Can be caused in one episode by severe overheating which can warp the head, or bad luck, which can cause the gasket to go. You may find that a compression check will show which side. H McCollister – Hide quoted text — Show quoted text – > Newsgroups: alt.autos.4×4.chevy-trucks,rec.auto.misc,rec.auto.tech > At first, I noticed that there was oil in my coolant recovery tank, but > there was no sign of coolant in the oil. Now that’s changed and the oil > has taken on that *milky* look on the inside of the filler cap. I’m > assuming that there’s a gasket leak allowing the oil and coolant to > intermingle (I don’t want to entertain the idea of a block or head crack). > My question: Is there any way to figure out which head gasket is leaking > other than removing the heads and visually inspecting? > BTW, the vehicle is a 1991 GMC Jimmy 4×4 with the 4.3L V6. > If anybody can help, I’d really appreciate it. > Thanks > Fred
Response:
my first guess Fred would be to run a compression check on all the cylinders. that may tell you which one is bad. all the cyl should be within 10% of each other. but you may have cracked a oil galley along a coolant jacket, or even a head gasket that let between an oil galley and water jacket. that would be tough to find without a visual inspection and magnafluxing the block or heads – of course that means removal of components. doesn’t sound like a head gasket break at the cylinder, because compression gases would leak into the water jaket and would increase pressure in the cooloing sys – to the point of blowing a hose…. etc. foam (a gazzilion air bubbles) in the coolant would indicate this try some type of additive to your coolant that seals small cracks. it may solve your problem long enough to get rid of that vehicle :-( good luck GA Sly US Army NCO Maint Tech
– Hide quoted text — Show quoted text -> At first, I noticed that there was oil in my coolant recovery tank, but > there was no sign of coolant in the oil. Now that’s changed and the oil > has taken on that *milky* look on the inside of the filler cap. I’m > assuming that there’s a gasket leak allowing the oil and coolant to > intermingle (I don’t want to entertain the idea of a block or head crack). > My question: Is there any way to figure out which head gasket is leaking > other than removing the heads and visually inspecting? > BTW, the vehicle is a 1991 GMC Jimmy 4×4 with the 4.3L V6. > If anybody can help, I’d really appreciate it. > Thanks > Fred
