3.4L Cooling leak, intake manifold or head gasket?

Question

Looks like I'm not the only one loosing a bit of cooling on this motor. Talked to an independent mechanic who said once it fails pressure test he would replace both head gaskets and the intake manifold, since he won't be able to find specifically where it is. Dealer tells me they can tell where the leak is, and if its only the intake (or even one head), save a bunch of work. Any opinions on being able to tell if it is only the intake?

The leak is almost certainly externally, as there is a faint whiff of that lovely Dextrol after running the motor.

<HLS · Accepted Answer

Chances are strong in favor of the intake manifold gasket, I think. That has been the tradition with these engines.

You have to take off the intake manifold to get to the heads anyway. Evaluate at that point. You can normally see where a leak has been occuring.

You can run compression and bleed off tests in the cylinders to see what the general condition is. If you get excessive leakage, then you may want to go deeper into the engine and see what the problem is. This could signal head gasket, cracks, or just poorly seating valves.

Occasionally you encounter a crack or gasket problem that doesn't open up very much, except at operating temperature.

shiden_kai · Answer

The reason the dealership says this is that they have probably done thousands of intake gasket replacements and hundreds of either one or both cylinder head gaskets on these engines.

It's almost "never" a head gasket leak at the combustion ring around the cylinder. It's almost "always" a cracked head gasket around the outside perimeter that leaks coolant externally.

And it's far more likely to simply be the intake manifold gasket.

Ian

3.4L Cooling leak, intake manifold or head gasket?

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