Bizarre coolant leak

Since I could not find this leak I have taken it to two different mechanics and they can not figure out this leak either. We replaced the coolant O ring on the right side of the head by the brake master cylinder but that did not fix the leak. The only time this leak happens is when I drive my car cold for just a few miles and then turn it off for a couple hours. Somehow in that time while it sits it releases about 10 to 20 ounces of G13 onto the ground. I have a skid plate so its really hard to tell exactly where the leak is coming from. If I reach my hand all the way around the head to feel the coolant lines there is no leak that I can tell. The timing belt was recently replaced along with the water pump so its not that. This has happened now about a half dozen times over the last 4 months. Now if I drive it more than 5 miles it does not do it. It only happens if I drive it a few miles and then let it sit. Then when I walk out I see the big puddle on the floor. Any ideas?

Run it without the skid plate, most problems are underneath, where we don't like to go.
Losing that much, you will eventually find it.

When mine did that it was a bad radiator, leaking between the tank and core on the driver's side.

As has been suggested, I drove it without the belly pan until I caught it leaking, then crawled underneath to identify the source.

Simon

I don’t know what a quality coolant system pressure tester costs nowadays as I bought mine about 40 years ago, but it has been an invaluable tool and a worthwhile investment I never regretted.

The one harbor freight sells works well but don't know the cost.

Have you looked very closely at the hard pipe under the IP? It's got an o ring that will sometimes leak.

The hard part is finding where it crawls from. You could try some die but you'll need to clean everything very well prior to

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Definitely a pressure test for this one.
After everything heats up equally there's no issue, however, with pressure on the system and not enough heat it comes out.
So, put pressure on and watch with the pan off.

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Good chance it is the coolant hose going to the EGR cooler. It runs across the front and then turns under the tandem pump. Leaky fuel will cause it to rot. The pressure is the way to go. You can pump it up and it won't be hard to see where the problem. Also look at your coolant temp sensor. My DD had a leak and it was the plastic clip had rotted and wasn't holding it in causing my leak.

joep1234 said:

Good chance it is the coolant hose going to the EGR cooler. It runs across the front and then turns under the tandem pump. Leaky fuel will cause it to rot. The pressure is the way to go. You can pump it up and it won't be hard to see where the problem. Also look at your coolant temp sensor. My DD had a leak and it was the plastic clip had rotted and wasn't holding it in causing my leak.

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I have done an EGR delete so its not that. I agree that pressure is the way to go.