Coolant Leak Help!

[derekw7]

I have a 99 4x4 Tahoe, 123k miles. Recently had some work done on the electrical and the mechanic said he thinks I need to have the intake manifold gasket replaced (which I know is common) because of a coolant leak.

Here's my question: After sitting for 3-4 days without running, I noticed a significant drop in the coolant level (the level in the tank dropped about an inch or so). If my problem is actually the intake manifold gasket, does it make sense that the coolant would be leaking even when the truck isnt running at all?

Thanks

[derekw7]

And, if you can, please explain it to me like I'm a 3 year old -- I'm an electronics guy and know zero about mechanics.

[777stickman]

Last time I tried to explain something to a 3 year old the only response I got was WHY?

So I'm going to speculate. When metal gets hot it expands and could be sealing the leak to a small extent. When metal gets cold it contracts which could be allowing the leak to increase.

In any case the coolant could be going into the cylinders and then into the oil which is not a good thing. Probably need to get 'er fixed asap.

[J-Ri]

It seems to me that the tank in these is not pressurized. That would mean that a coolant leak will not immediately lower the level in the tank. Are you checking it hot, then leting it sit 3-4 days and then checking it cold? The radiator cap keeps the cooling system pressure at a max of 15 PSI and a min of 0 PSI. When the truck heats up, some coolant is allowed past the cap (thermal expansion) and into the tank. As the truck cools down, and the pressure reaches 0 PSI, the cap allows coolant to come from the tank back into the cooling system.

Are you adding coolant? The intake gaskets can leak anywhere from where it's wet around the gasket, to where there's a steady stream coming out (if you're lucky, on the outside of the engine.

Look on the front of the engine. On each side there is a valve cover. Now, looking at the valve covers lengthwise, the aluminum part just towards center of the engine is the lower intake. Follow the edge of the lower intake, and if any part is leaking even a very small amount of coolant, I'd replace the gasket.

This is really one of those things where you either have to do it yourself, or trust the guy doing it. Unfourtunately, not everyone can be trusted.

[Tmann22]

Yes that is exactly what it is. I had the same problem with mine. Intake Man gasket. It will cause a drop in fluid. B/c it actually leaks back into the engine also and on the outside. Get a outside mech to do it. A dealership will rip you off. It is a big job 4-5 hours. both ways.

[wafrederick]

It is Intake gaskets and a very common problem.Fel Pro has the best upgraded intake gaskets,made out of metal instead of plastic and last longer.They are more money but worth it if you do not want to have them replaced anymore.Jasper,the best reman engine reman company out there even uses them and threw every plastic intake gasket out that they had left.Have the water fitting replaced too,the one from factory is made out of pot metal which breaks real easy and and the replacement is made out of steel.The timing is not adjustable and the distribitor is set with a scan tool.Look for cam sensor retard and the spec is 0 or -0 degrees.Mark the distribitor before pulling out.

[Tmann22]

Its also a good Idea to replace the water pump and some hoses and fittings while the top of the engine is off.

[NoEcm]

Here is an excellent article:

http://www.market-place.com/intake/intake.htm


It explains the different types of Intake Manifold leaks and how to repair it.