Head Gasket ???

[Deano2711]

Never had any trouble from my Golf until today !!!!!!!!!!  The temp guage has never gone above the halfway mark on the guage. Heaters all working as they should. Recently I have noticed a build up of pressure when removing the expansion tank cap even when the engine is cold. Today I went out for a drive and when I returned home I noticed a slight dribble up the drive so turned car off and went to have a look under the front splitter to try to see where the water was coming from. Then I noticed that the water was pouring out from the expansion tank with the lid on.
So I take off the expansion tank cap and let the car run for half hour or so and no trouble except the water then starts to come out of the bottle with the lid off and is like a boiling kettle. I topped up the water and replaced the lid and let the car run. I then noticed the temp guage creeping up (slowly). It got to three quarters of the way up the guage then fans kick in and down it comes. Heaters are still blowing red hot air and the top and bottom hose are both hot so water is circulating ok. Do need to add I believe I have a water leak from around the water pump area and this is on the to do list but I am not sure this would affect my problem.

Any one had a similar problem and views welcomed. Plan is to have a drive in the car tomorrow to see what happens and if the gasket has failed will speak to my mechanic to get a price but could do without this as I am off on jollys in a couple of weeks.

[Wayne]

It does sound like it is building pressure so I think you may have a HG issue

[Bandit127]

Head gasket to water circuit failure usually means the water level goes slowly up and down like something is breathing.

Don't know why this happens - but it is horrible to see when it is happening on your car. Like some Stephen King monster has moved in to your engine...

[JC]

compression test, and sniff test, but dont go straight for H/G .

oil coolers can fail too  give similar symptoms as h/g failure

[Deano2711]

Might not mean a lot but got no oil/water mixing, no smoke and no loss of power. Everything is working as it should and the water is nice and clean too with no nasty smells or anything. I had a very similar problem on a Mark 4 which is what got me thinking but the Mark 4 had no heaters whereas this one is blowing red hot. When driving it today everything was as normal until I reversed up the drive. I was thinking air lock before as I have been topping it up a couple of times per week due to the water leak. I keep it topped up regular. That is why I run it without the expansion tank cap on for a bit and it was all fine then but after running for a good half an hour without the cap then I put it on and left it running with no problems. But when I turned off the engine and removed the tank cap there was a bit of pressure there but not as much as the last week or so. Maybe an air lock but as said I will take it for a drive tomorrow to see what happens. Any tips for testing or things to look out for ??

[Bandit127]

As Chuff's answer.

Don't assume the flowing out like a kettle is due to HG. You were running it for a long time without the cap on - it was not designed to run like that.

Also don't expect it to hold on to water much more than 1 or 2 cm above the min line on the reservior. It will throw out anything over that through the overflow.

TBH - if it was mine I would run it while it is running OK and keep a close eye on the water level. Book a compression test and coolant analysis ASAP.

[itavaltalainen]

Do you have a steady stream of water coming out the thin hose at the top of expansion tank?
If you have a water pump with plastic impeller this could have come undone from shaft, I have seen this before..

[gladysp200]

It does sound like it is building pressure so I think you may have a HG issue

[Gavv8]

If the H/G has started to let go from a bore to a waterway then you would get the build up in pressure without the the oil/water symptoms but the latter is sure to follow.
I'm not sure how the waterways/oilways are configured in relation to the bores but its the most likely explanation although my brother had the same thing happen on his focus recently and that turned out to be a cracked expansion tank.

[Deano2711]

If the H/G has started to let go from a bore to a waterway then you would get the build up in pressure without the the oil/water symptoms but the latter is sure to follow.
I'm not sure how the waterways/oilways are configured in relation to the bores but its the most likely explanation although my brother had the same thing happen on his focus recently and that turned out to be a cracked expansion tank.

Thats why I conpared this to my old Mark 4 which had identical symptoms except for the heater. Will take her out for a test drive in a bit to see whats gonna happen.