Positive Test for Blown Head Gasket?

I have a '94 Camry with the V6 engine and about 100K miles. Over the past year it has begun losing coolant at an increasing rate. I check fluids etc once a month. At first I was adding about 6-8 oz of coolant each time. This has increased to a one-and-a-half pints.
Now, by the time of the monthly check the reservoir is empty and the system isn't full.

I've examined all the hoses and fittings and see not evidence of leaks. Revving the engine with the cap off the system pushes coolant out, but there are no bubbles. I don't see any white exhaust after the car's hot. I drained a half-cup of oil and see not evidence of water. As I understand it these are classic tests for a blown head gasket and none are show anything.

I've read that a bad cap can cause loss of fluid but I can't see how it can do that without the reservoir being almost full immediately after stopping the car and it isn't.

Are there any other possible causes?

How can I be positive the gasket is the problem before replacing it?

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

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

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.

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

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.

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

according to instructions for a vacuum guage if the needle is fluxuating rapidly at all engine speeds the head gasket is leaking. I put the diagnostics for vacuum guages in a file on my website. Look at www.ncf.ca/~ag384/vacuum.txt. You can also get to it from my homepage listed below.

Thanks. That seems like the answer.

"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.

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.

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.

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.

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.

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

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.

A garage will do a pressure test. They put an air line into one of the

Is this the same as a cylinder leakdown test?