Constant bubbles in water

[twzted_gst]

When I take my water cap off I have constant bubbles and the bubbles look frothy. Also when I take oil cap off there isn't as many bubbles. Any ideas? Blown head gasket?

 

[low_n_slow95]

Yea thats what I thought just wanted to make sure thanks for the heads up

 

[2ndGenTurbo]

try block testing it... it's a tool that has a rubber cone that stabs in where the radiator cap is, then a clear cylinder that u fill with a special liquid to a line, then a cap and you squeeze the ball on the cap that creates a suction in the liquid and it detects exhaust gas in the coolant... be careful not to get actual coolant in the tester as this will falsify results. if the liquid changes color (with out coolant contamination in the liquid) the there is head gasket leak for sure

 

[low_n_slow95]

Damn that's pretty highspeed, I'll shop around for one this weekend

 

[2ndGenTurbo]

I got mine of the snap on truck but they're available at most part stores

"block tester"

 

[Calan]

A compression test will tell you if you need to do a leakdown test.

Not necessarily.

I just had my head gasket start pushing coolant last week, and the compression test showed all cylinders great at 180-185 psi. The leak-down test showed cyl #1 leaking into the coolant though, which was verified when the head came off.

A leak-down test will find smaller problems and is usually the better choice out of the two. Compression tests are good for finding "big" problems that drastically affect cylinder compression, but they won't show smaller issues or more dynamic problems.

My case was a good example; I could only find air leaking into the coolant if enough pressure built up in the cylinder over time, at which point it would push past the head gasket and into the coolant. It then took about 10 seconds for enough pressure to build up again and cause more bubbles. By injecting air into the cylinder continuously at high enough pressure I caught it, but a compression test would never show any symptoms of that type of problem, unless maybe someone caught it while watching the coolant carefully during cranking. Even that isn't likely though, since the pressure generated from cranking will leak away almost immediately as the valves cycle.

This makes a lot of sense when you think about it. During a compression test, you are only building the same pressure that compresses the air/fuel mixture (usually 100 to 200 psi), and it's momentary. But when the engine is running and combustion is taking place, peak cylinder pressures are MUCH higher; maybe in the range of 1000-1500 psi, depending on amount of boost, fuel, tune, etc. The typical sample-and-hold comp tester that is used while cold cranking the engine will never find problems that only show up at these much higher pressures and temperatures; especially if they take time to locate.

 

[Black'95]

Not necessarily. I just had my head gasket start pushing coolant last week, and the compression test showed all cylinders great at 180-185 psi. The leak-down test showed cyl #1 leaking into the coolant though, which was verified when the head came off.

A leak-down test will find smaller problems and is usually the better choice out of the two. Compression tests are good for finding "big" problems that drastically affect cylinder compression, but they won't show smaller issues or more dynamic problems.

My case was a good example; I could only find air leaking into the coolant if enough pressure built up in the cylinder, at which point it would push past the head gasket and into the coolant. It then took about 10 seconds for enough pressure to build up again and cause more bubbles. By injecting air into the cylinder continuously at high enough pressure I caught it, but the compression test would never show any symptoms of that problem.

Aha! I wonder if that's my problem; my compression test came back good, with similar numbers to yours, actually. After I give 'er a footful, I almost always smell coolant, but I never smell it while I'm under boost. I can't keep coolant in the damn thing, and if you take the radiator cap off, it looks bone dry, but NEVER overheats, no matter what the outside temp is. I've long since given up filling the coolant up. No leaks that I can find, either. The temp gauge never moves past normal, even when I was at the track doing 3-4 back-to-back runs... It runs fine, other than smoking when it idles for too long. I think that's from bad valve seals, though...

 

[Calan]

Aha! I wonder if that's my problem; my compression test came back good, with similar numbers to yours, actually.

Do a leak-down test; you'll be amazed at what you can discover about your engine.

 

[low_n_slow95]

thanks for the advice i picked up a block tester at work today. gonna knock that out asap, now i need to find a compressor to do a leak down test. i have a feeling that im about to rebuild a motor fml

 

[Absit]

Interesting, thanks for the information calan.