What are some ways to diagnosing a blown head gasket that you can do from home?

I don't have a leak down tester/air compressor. I was hoping to figure out some other ways to do it...

It isn't smoking, but it is also full of water and not antifreeze.

you pop the cap off of the radiator, and it bubbles, as if it is boiling, but it is overheating, so it could very well just be boiling...
(its on a 97 jetta, so it isn't really on the radiator, it is on the fill tank... VW's are weird)

no water in the oil
no oil in the water
no leakage down the sides of the block

any ideas?

thanks

 

Any coolant/water loss at all?

Fans coming on? Thermostat working properly?

There are countless things that could lead to a car over heating, check/replace the least expensive things first.

Also check the cap, your coolant hoses, etc.

 

Your car overheating at idle, how long since you last put in a thermostat? Get your system pressure tested asap. Depending on the leak, you might need to have a new gasket or a seal additive put in.

 

1.Look for differences in the spark plugs.
2.Crank it over with the plugs removed to see if water spits out.
3.Look for "chocolate milk" in the oil or water.
....and what those guys said...-Bob

 

If you have a 7M, its very likely you have a BHG.

Honestly it could be a radiator cap.

 

just replaced
the water pump
the thermostat
the radiator cap

the radiator flows the way it should
no leaks, until it over heats and the pressure builds up

the heater blows hot while everything is ok, but as soon as the flow gets messed up, from what I was thinking was vapor lock, it stops blowing hot.

the fans are wired to a manual switch so i could rule out the bad temp switch.

you can fill it, run it. let it cool down, top it off, and drive it for 30-45 minutes without a problem. then the temp gauge will just raise and raise til it is pegged out. you get it parked, and pop the radiator cap and there is significantly less water, around 3/4 of a gallon. it takes just over 1.5 gallons to fill it.

I was thinking headgasket because when you let it idle with the cap off, it bubbles, as if it is boiling. you can touch the water and it is warm, but not boiling hot. Then it warms up and just spits water all over the place. I was thinking it was just air getting pushed through, but it doesn't ever seem to stop. As in, there isn't ever enough water to fill in all of the places bubbles are. I just wrote it off as VW's being a pain to bleed the air out and every time you take the cap off, it sprays some water out because of the change is pressure.

 

If you have a blown headgasket I would think you would have loss of compression in one or more cylinders. A blown gasket doesn't always mean you are going to have coolant/oil cross contamination.
Get a compressioon checker and a Haynes manual (for the compression specs.)
With the checker screwed into the spark plug hole you can turn the motor over (but not start it) and have some else watch the gauge.

I think you can borrow a compression check gauge at Discount Auto or the other stores. Basically you buy it, use it, and they give you your money back when you bring it back.

 

yeah, but a compression tester isn't going to narrow it down to the headgasket... that will also point to vavles and seals and all that fun too..

a leak down test is the only way to test for it, at least accurately....

 

Sure, bad compression won't narrow it down to just being a head gasket, but it will start to eliminate the variables. Combine a leak down witha compression test and really narrow it down, But, if you really want to know if it's the head gasket thats causing your issues then you'll just have to pull the head.

 

Theres all kinds of things that happen when you have a blown headgasket. This is another test you should try before pulling the head, but it does seem like you have a blownhead gasket.

UVIEW 560000 Diesel & Gas Combustion Leak Tester Kit - eBay (item 200276192949 end time Aug-12-09 12:30:48 PDT)

you can pick these up at parts stores locally.