mk 4 golf 115 tdi losing coolant

[key-matic]

hi all, anybody any clue why when i take the car for a good run on motorway, say a 100 miles, athe end of the journey the stop sign on the dash lights up to tell me i need more coolant. it doesn't need a lot maybe a pint or 2 to top up, this has happened numerous times now and have tried remedying it by putting on a new rad and new coolant bottle. yesterday returning from a journey as soon as i hit the motorway the car seem to develop flatspots and tried to overheat ( went to 130 instead of usual 90 on indicator) had to pull over twice (very briefly)then it seem to sort it self out for the rest of the 100 miles home. any ideas anyone PLEASE

[Cam]

Could be the coolant pump?

I hear the VW/Audi OEM pumps are pretty soft and can fail early on in life.

If the coolant is appearing/ disappearing in lare volume like you say could be this and/or air-locks.

Cheers

[gurpalbasra]

I had this problem on my Mk3 TDI and it turned out to be the head gasket only ever lost coolant on high speed motorway driving. You need to feel around under the coolent bottle and if it feels wet and oily it is being pressurised out of the bottle when the engine pressure goes into the cooking system.
G

[doriclad]

I am having exactly the same problem.

The car did quite a lot of motorway driving a couple of weeks ago during holiday. I then drove it around locally last week for work and everything was fine. However, at the weekend when I went to York on the motorway (1.5 hour drive) the coolant bottle was almost empty on arrival. It was the same on the way back from York.

I have topped it up and it doesn't seem to lose water whilst sitting unused. If I drive it locally to work it still doesn't lose any water. It only seems to happen on long fast drives.

When the car had been sitting stationary for just over 3 hours after a short local drive I opened the coolant bottle and there was a hiss / release of pressure. So it does seem to be holding some pressure within the system.

I can't understand what the problem is, so will have to take it to the garage for diagnosis. I would be interested to hear any other views and to hear how you get on with the problem.

[doriclad]

PS. My car is also a Mk4 TDI 115 with 50k miles. It has never gone above 90 on the temp guage - even on the long run. When the level gets low the warning light does come on, usually when I have stopped or restart the engine.

[nash997]

I am having exactly the same problem.

The car did quite a lot of motorway driving a couple of weeks ago during holiday. I then drove it around locally last week for work and everything was fine. However, at the weekend when I went to York on the motorway (1.5 hour drive) the coolant bottle was almost empty on arrival. It was the same on the way back from York.

I have topped it up and it doesn't seem to lose water whilst sitting unused. If I drive it locally to work it still doesn't lose any water. It only seems to happen on long fast drives.

When the car had been sitting stationary for just over 3 hours after a short local drive I opened the coolant bottle and there was a hiss / release of pressure. So it does seem to be holding some pressure within the system.

I can't understand what the problem is, so will have to take it to the garage for diagnosis. I would be interested to hear any other views and to hear how you get on with the problem.

DID YOU FIND OUT WHAT WAS CAUSING THIS FAULT BECOZ I AM HAVING THE SAME FAULT ON MY GOLG MARK 4 GT TDI

[nash997]

hi did you fix this problem with the coolant because i am having the same problem can you please tell me your findings .
thankyou

[doriclad]

Thankfully I have now got the problem sorted.

In my case it was a blown head gasket. I had been checking the water and oil regularly but could see no problems. I drove it to Aberdeen and left it with my mechanic who after driving it around for a week managed to diagnose the problem. Basically the fault became more apparant the more the car was driven.

Early in the week the mechanic had done some tests but could not find any leaks or problems with the coolant system. By mid-week he was saying that where everything appears to be ok but the car is continuing to loose coolant it can be a porous head gasket. However these are difficult to test/diagnose and are only proved faulty by replacement. This was going to cost a massive £2000 which even included his low labour rate and parts sold on at cost price.

I hope you manage to find what is wrong soon. It is very frustrating as it can be something inexpensive like the seal on the expansion tank to something expensive as a porous head.

If it were a porous head then I did find out that there are some companies who can inject a resin into the head to seal the holes. This was costing about £300 and may be worth trying.

Best of luck.

[onzarob]

Rob ;o)