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Coolant in spark plug well


Junior Member
Thread starter #1
Hello, I am new to the site.

I have a 2001 LS, V8 with about 170K miles, it has mostly been a good car. About a year ago I started to see coolant in the spark plug well of cylinder 3 (car missed badly). I added some stop leak and dried out the well which fixed the problem, but in the process it plugged up the heater solenoid control valves. Since I live in sunny California, I did not notice the lack of heat until winter. I replaced the solenoid valves and flushed the coolant. Of course, the leak is back. I pulled off the intake manifold and everything looks dry, no leaks anywhere. One odd thing I noticed is that all the ports on the manifold and the engine have a thin lining of a shiny wet film, kind of like you see on carburetor throttle bodies, except for the ports related to cylinder 3. Those are bone dry.
I suspect I have a cracked cylinder head, in which case the car will probably be sacrificed. Does anybody have an explanation for what I am seeing?

If you put on a brand new cylinder head on an engine with all those miles, that thing is a ticking time bomb for the lower end. I warned two people who had similar issues with head gaskets. They put new heads or refurbished heads with low miles and within 2 months the lower end went kaboom because it could not handle the pressure of the newer head. If you put on new heads, then you need to overhaul the entire engine. If you love that car, it may be worth putting a re-manufactured engine in it from these people who make them for the LS. I, myself had the same issue with a car I had 20 years ago before I learned of such things. My engine had almost 200,000 miles. My cylinder head had a leak. I bought a new gasket set and found a cylinder head from a junk yard that had 74,000 miles. Within 3 weeks I was driving at 30 MPH and the engine threw a rod as I was passing through an intersection.


Senior Member
Ottawa Ontario Canada
Welcome to the Forum.

From your description I would suspect a coolant leak from the throttle body adapter. The attached file shows the Coolant flow and includes a diagram of the coolant flow showing the engine parts. You will notice in the V8 flow diagram a throttle body adapter (item 10) which has input and output coolant hoses. The "wet surface" of the intake is hydrocarbons which can be shiney. The reason #3 cylinder does not have the hdrocarbons is that coolant in a very small amount is leaking into the intake for cylinder #3 and cleaning it (coolant is a particularly good cleaner in an engine but it will take out bearings in sufficient quantity). There may also be an exterior leak allowing coolant into #3 plug well. Not had much experience with the LS, so its an educated guess.

Good luck.


Does that go through the throttle body to keep the air warm as it goes in similar to what I've seen some GM cars do?
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