Positive Test for Blown Head Gasket?

I should add the car idles smoothly and the operating temperature is the same as always.

jim

One other test is to pull the spark plugs. If you find one really clean, coolant has likely gotten to it.

You also can go to a rad shop and have them pressure test the system.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

jim evans wrote:

jim evans melodiously murmured in news: snipped-for-privacy@4ax.com:

A garage will do a pressure test. They put an air line into one of the spark plug holes and blow air into each cylinder in turn, with the rad cap off. When air bubbles start coming out of the rad cap opening, that's the one that has the bad head gasket seal. If none of them leak, the head gasket is fine.

--

------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage:

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That would be a compression leak though wouldn't it?

Headgaskets don't all blow out into the cylinders. They can leak externally or in-between the oil and water channels.

Mike

"William R. Watt" wrote:

Thanks. That seems like the answer.

jim

Is this the same as a cylinder leakdown test?

Exactly the same test except that you're focusing on any relative movement of coolant level in the radiator.

No it's not!

A cylinder pressure or leak down test will only show a blown compression leak in the head gasket o ring around the cylinder.

It will 'not' show other types of head gasket leaks!

The OP needs a rad pressure test, not a cylinder test.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

You need to focus on the question that Neil was actually answering. He wasn't making any statements about whether the above mentioned procedure would find "all" types of head gasket leaks, he was simply saying that..."yes"....the test is essentially the same as a cylinder leakdown test.

Actually, a combination of the two would probably be helpful. But, really...if you go back and read the original post, you can see that the guy is complaining about loss of coolant with "no" visible external leaks. Since he doesn't see anything in the oil, I think it's safe to assume that he's probably consuming it through a cylinder.

I would add another test into the mix....we used to use it quite successfully on Chrysler products...we referred to it as a "block" test. Just a liquid in a tube that was inserted into the rad cap hole of the radiator, if there was combustion gas in the cooling system, the liquid would turn from blue to yellow.

Ian

"shiden_kai" melodiously murmured in news:Kbhmb.1092$zx2.484@edtnps84:

There are fluorescent dyes used for that purpose as well. If the pressure test passes, they will probably try putting the dye into the coolant and running the engine for a while. Afterwards, a black light will be played around the hose ends and such to see if anything glows. If it does, there is a tiny leak that only leaks under pressure, and the leakage gets boiled off by engine heat, making it difficult to detect.

Really?

Into the cooling system, which is exactly the concern here.

Then it is the appropriate test since there are no other driveability problems mentioned by the OP.

Fine for an external coolant leak, but pumping the radiator up to 15psi is not likely to produce any meaningful results WRT locating a minor head gasket leak.

"Tegger®" wrote

That's a different kind of test all together. The one I was thinking of, tests for combustion gas in the cooling system while the engine is running. We do also use your method, but it's mainly for simple external coolant leaks.

Ian

[Good things done, and other good additional suggestions, deleted, such as checking the plugs and having the cooling system pressure-tested]

---and as long as you've got the plugs yanked, might as well do a compression test.

A trick I've heard about but never had occasion to try, for diagnosing a certain class of otherwise cryptic head-gasket headaches, is using an emissions probe to look for exhaust gases in the coolant . The only way they can get in there is if the exhaust is communicating with the cooling system through either a puny gasket or (eek!) a crack.

You might also try settling in with a good book and occasionally throwing an eye on the cooling system as it cycles from full cold to full hot and back down again, just to make sure it isn't puking out the reservoir under circumstances that prevent you from noticing. Take a good look at the vicinity of the heater core too when doing this. It's a no-tools, almost-free initial check and thus is probably worth your while as a first step.

I've had cars run just ducky for a long long time with a small

*consistent* amount of mysterious coolant disappearance, but since you've noticed it getting worse recently, your decision to pursue the problem is a wise one.

Cheers,

--Joe

This is a phenol/"sniffer" test, sometimes called the "Snap-On Test." NAPA and other parts houses sell these.

CO/CO2 will cause the reaction. The test is reliable, but somewhat expensive and difficult to perform correctly.

GTr

Thanks for all the replies.

When they pressurized the radiator they found a leak along the bottom right end of the radiator. It leaked in a place that can only be seen with a mirror.

So, now to find a radiator.

See my next post.

jim

You are right, I didn't read that right.

Mike

Neil Nels>

Don't forget having a sample of the motor oil tested by a lab for traces of coolant. This costs about $20 and will take a little over a week to get the results:

--- Bror Jace