Originally Posted by Dv8
-check headgasket by doing a compression check and/or leak down test.
Another sure-fire test for headgasket failure is to take the car to a mechanic who also does smog checks. Make sure the engine is fully warmed up...its even better if you've been driving for a while. Also make sure you've got a good radiator cap..no leaks allowed.
Your mechanic can use his smog "sniffer" to test for hydrocarbons (combustion gases from the cylinder) getting into the cooling system...he sticks the "sniffer" probe into the air space at the top of the coolant reservoir. If HC's are detected in the reservoir air...they can only get there by leaking past the headgasket.
To me this is a lot easier to understand than compression and leakdown tests. Leakdown can also be caused by rings and/or valve problems..and you or your mechanic really need to know what you're doing to tell what's really going on and know the difference.
There's also a simple chemical DIY hydrocarbon test kit that you can buy from most MAC or Snap-On tool trucks. About $55.
It's kinda' like a "turkey baster" thing ....a glass tube with with a rubber squeeze bulb at the top. Pretty simple device. You put a special chemical inside of the glass tube of the turkey baster ...it also has a fat hard rubber cone shaped nozzle at the otherend . Warm the car up to full op temp. Then jam the cone shaped end into the filler hole of the coolant reservoir and squeeze the rubber bulb....this sucks air from inside the reservoir into the glass tube and it bubbles up through the chemical.
If there are hydrocarbons in the air in the coolant reservoir...the chemical turns color (blue I think)....indicating HG failure.