A cylinder head gasket can fail in a number of ways, some of which will show up in tests and some won't - especially if it's in the early stages of failure (have a look at the diagram on http://www.agcoauto.com/content/news/p2_articleid/200 for some more info!)bikesnbones wrote:I took my car to another garage yesterday owned by the father in law of a work colleague of mine.
He did a test that involved attaching a tube filled with blue liquid to the expansion tank and idling the engine for 10 minutes.
If the liquid turns brown, it means head gasket failure but if it stays blue, it's fine.
Mine stayed blue.
I didn't see what the other garage did but he reckoned it would have been the same test.
So now I'm very confused.
The test you describe sounds like a hydrocarbon test - it's basically a check to see if there are any hydrocarbons (or combustion gases) in the coolant.
If there are, it would indicate a leak between one (or more) of the cylinders and the water gallery, so when the gases get compressed by the piston they leak into the cooling system - and when the gases get ignited and force the piston down, they also force their way into the cooling system. Therefore, this kind of leak is often accompanied by overheating and/or missfiring. As you dont have either of those symptoms yet, it either means that:
1) You don't have this type of failure
2) You do have this type of failure but it is at a very early stage so is only leaking a small amount that may not trigger the colour change, or is only leaking under certain conditions.
As you are loosing coolant, do you know if anyone has done a pressure test? This involves taking off the pressure (radiator) cap and attaching a tool that you use to pump up the cooling system, then leaving it a while to see if the pressure drops. The ones I've used are like a big bicycle pump with a guage attached. If the pressure drops, then there's a leak. The rate of drop should tell you how bad it is, and the faster the drop the easier it will be to find!
