I have been smelling a slight coolant odour when coming off the highway lately. Not much but it happens every time I go from 70 MPH to a stop. I stuck my nose everywhere I can think of that would leak and I can't find any thing external so I am worried about the head gasket. I did a compression check and got 180-185 for all. Plugs look consistent except for #3 which is a little yellow (middle in the following photo).

I am not burning any oil or coolant and I don't see any water in the oil or oil in the water.

No overheating issues.

Am I imagining things or could the HG be starting to go? I'm taking the car to Texas Motor Speedway for a track weekend next month so I want to make sure that I catch anything that may give me issues before I hit the grid.

I find it hard to believe that head gaskets fail on N/A motors after seeing the punishment they take in my L28ET. I would first investigate traditional leakage points, as in the heater hoses/core, radiator, water pump weeping, which is often dried up by the time you open the hood. Look for "slug trails" of where coolant may have dripped and dried. Carefully monitor coolant level in the overflow, and if your radiator cap is old, go get a new one.

Edited April 24, 201114 yr by cygnusx1

I had a similar situation and found that my head gasket was leaking at the very back of the head. You could see the coolant residue right above the starter and a water trail down the block. No leakage in to or out of the cylinders though, just some steam and syrup smell from the back.

I fixed it with some Barr's leak stopper (don't hate, my car is a rolling experiment in how things work, a reason to go to the auto parts store or roam the junk yard. Every "problem" is a new adventure). After about half of the bottle of sealant powder extruded itself out of the gap [a couple of months], leaving a pile sitting on the block at the back of the head, it sealed up.

I just did a pressure test of the radiator and found that it went from 15psi to 13.5psi in 10 minutes. I don't see any leaks but I am loosing pressure somewhere. I'll check the back of the head as you suggest.

The system wasn't cooling off when you tested it, was it?

Yes it was. Should I test cold?

Yup. System drops in pressure naturally as the gases shrink in volume while cooling.

Crap! Should have thought of that.

I have used Barr's Stop Leak in a number of cars with great success.

I used radiator stop leak powder one time in the past. It stopped the leak but two weeks later my thermostat stuck open. Could be a coincidence but I'd rather find the leak and fix it in this case.