I bought a nice cheap Pontiac Aztec, which had overheated and the shop that towed it says it needs a head gasket. There is coolant residue on the oil cap. Other sources suggest the coolant could have come from the intake gaskets and run past the cylinders. Anyone have experience with these? Has anyone changed the head gaskets? It’s quite tight under the engine hood, but Chilton’s doesn’t say anything about pulling the engine. Unfortunately the book has obviously missed some details…
If you are doing the job yourself, as it sounds like you are, just replace both the intake and head gaskets. Make sure you use the improved metal gasket for the intake. Refill with green coolant, forget about Dexcool.
Not knowing how long this vehicle was driven with a leaking gasket (regardless of type) you’ll have to have the crankshaft bearings and journals inspected for damage from the coolant/oil mix.
How badly overheated did the engine get? Is the head warped? Hopefully that will show up (or not) when the engine is stripped down. Questions, questions and more questions.
This means checking further than the head.
Which engine? The GM 3.4L V6 can be rolled ahead about three inches to allow some working space although it will still be tight.
A total coolant flushing and a oil and filter change is a must. Removing the oil pan to ensure all the oil/coolant is removed is a good idea but can become expensive due to the labor involved.
A lot of people prefer to use the old standard green coolant rather than the GM Dexcool but that’s personal preference.
I had the intake manifold gasket changed in my 2000 Olds Silhouette 3.4L and replaced the removed coolant with new Dexcool and have had no problems since. That was in Sept/'04.
Note: I don’t wait the five years GM claims it’ll last before changing, I do it every three.
I agree with Roadrunner about a possible crankshaft and crank bearing problem. Coolant diluted oil can ruin the crank and bearings and if the engine suffered severe and/or chronic overheating it’s possible the cylinder walls are ruined along with the pistons and rings. In a nutshell, it would need an entire new engine.
Without knowing the entire Gospel truth behind the problem, simply replacing the head gaskets is a coin flip really.
A compression test could be performed on all cylinders (both a wet and dry test). A head gasket fault would affect several cylinders but if all cylinders come up pretty low on the numbers (and if those numbers increase dramatically with a squirt of oil) then the rings are fried. At that point you would know for sure that head gaskets only are not going to solve the problem.
Head gaskets can be replaced with out pulling the engine. But by the time you have disassembled enough of the engine to get at the Head gasket there will not be much left in the car. To check bot bure the head gasket is bad do this 1. Do a compression test on all cylinders. Pressure should be with in 20 psi of each other and none below 80 PSI. Should be around 100 - 125 psi with all plugs removed and a strong battery. 2. Inspect for a brown milky color on the dip stick. 3. with the enigne cool start the engine and remove the radiator cap. Look for bubbles in the coolant. If they are continously present suspect a blown head gasket.
Coolant in the oil does not necessary require an engine rebuild. A compression test and oil pressure test should be performed to gain more insight to the condition of the engine.