Head Gasket Suspect

[Guest iancar]

got a 1999 tdi galaxy with 74,000 on the clock, i am now loosing water which appears to be overflowing from my expansion tank, this is only apparent by the appearance of water under the bottle, it takes about 1 week to go from full to refill and there appears to be a small build up of fine carbon dust in the water filler cap, has anyone got any ideas on what the problem could be? it has been suggested it might be the head gasket, i,m not loosing any power though?

 

help

Ian

[dipsomaniac]

Is car overheating before erupting coolant?

 

Check for other signs of head gasket failure - exhaust gasses/oil in expansion tank, water in the engine oil or exhaust emitting white smoke/steam.

[Guest iancar]

no car seems to be operating fine in all respects, no overheating or signs of water in the oil, no white smoke from exhaust just some black smoke on hard acceleration, the water dosn't seem to be bursting out of the expansion tank it more like escapes by stealth over a week or so.

 

cheers

ian

[paulmpaciorek]

Is it possible that there is a small split or hole in the expansion tank ??????? :huh:

[dipsomaniac]

Try a new expansion tank filler cap.

[Guest iancar]

I have replaced the expansion cap recently this dosn't seem to be making a difference.

 

cheers

ian

[seatkid]

Please give us your definition of "full" and "refill"......

 

Do not fill above the maximum line, this is just over the halfway "joint" of the expansion tank. A lot of VAG cars however tend to vent off water till it settles at around the "minimum" mark which is about an inch under the halfway "joint". Its perfectly ok to leave it at this level.

[johnb80]

I'ts also possible that you have an airlock in the system somewhere. When you run the engine the air expands shoving the water out, switch off the air cools and the water level drops. Attach a plastic bag to the vent pipe of the expansion bottle and keep checking it's contents. If you find water in there you know it's venting off via the cap in which case another new cap / bottle / test for exhaust gasses. Double check that the cap is the right one, if the pressure rating is too low it may boil the water off in traffic.

 

Regards - JB

[Masked Marauder]

no car seems to be operating fine in all respects, no overheating or signs of water in the oil, no white smoke from exhaust just some black smoke on hard acceleration, the water dosn't seem to be bursting out of the expansion tank it more like escapes by stealth over a week or so.

 

cheers

ian

If the head gasket was pressurising the coolant then normally you show a slight overheat when you put a lot of load on the engine. This is because of the build up of pressure in the cooling system.

 

If the gasket has failed between a waterway and a cylinder then it may be allowing a little water through into the cylinder where it is ending up as steam, your only loosing a little water a week at this point, so it would not smoke like a traction engine.

 

But headgaskets have a wide range of symptoms and you may get some of them and you may not. Often headgaskets are missed as a problem because people are not getting all the signs of failure, where there are infact many different signs of failure. Why if the gasket failed between a cylinder and a waterway would you get oil in the water?

 

But headgaskets also get the blame for things when they are not at fault because the home mechanic mis-diagnoses the real problem.

 

The only way you can rule out the headgasket in your case would be to have a chemical test done that detects exhaust gas in the coolant. But as you are not showing a rise in temperature on the gauge my gut reaction is it is unlikely to be the problem, but then I am a DIY mechanic......

[Guest MATT]

I had a similar problem, i was loosing coolant, i found out, that the cap wasn't on fully. i had turned it until i felt resistance, but then, you try and force it round, and it clicked, and went round again, giving a tighter seal - it was because of the 'steam release' gap, that had fooled me.

 

So, just see if you can turn the cap anymore.

 

MATT

[Guest iancar]

just made sure it is v tight, i'll keep an eye on it for the next week or so.

 

cheers

Ian