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234 Posts
Discussion Starter · #1 ·
I was advised:

But elsewhere I read:

Another way to check if you have a blown head gasket, or a cracked head, is to start with a COLD engine. Start it up, and run it for about 30 seconds. If you have something wrong, it will pressurize the radiator. Open the cap, and listen for the pressurized air to escape. It will make a quick PPFFFTTT sound for 1/2 second. Just don’t do this with a warmed up engine.

I gave mine more time, 90 seconds. Stopped the engine, quickly opened the cap, no pressure heard. I know the system holds pressure. I did what they say never do, removed the cap when hot. Plenty of pressure heard then. Coolant expanded higher too.

Some people say they can run at 2500 RPM for 5 minutes without coolant overflow from the expansion tank. Other people say pressure is expected when the engine reaches operating temperature, and coolant will overflow. That's why they say NEVER open the cap when the car is hot. At 2500 RPM my engine reaches operating temperature before 5 minutes. So that method of bleeding air doesn't work for me. It must self bleed during operation though. I don't overheat.

As for a head gasket leak, the quick test given above does not show it. What do you think, reliable or bogus?
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