A4 tdi Coolant Expansion *Help*.

[Ianh1]

Hi All,

Just to keep everyone up to date, firstly thanks for you help and my appologies for the delay in keeping you updated with progress but I have been building an extention on my house, anyway I replaced the filler cap and that made no difference the car was still blowing out coolant when hot (i.e revs at a consant 3000 plus not at tickover) however the temp gauge remained at 90 deg and would only venture over after a long journey (50+miles) at "motorway" speedand after loosing a little coolent.

So bearing in mind that the thermostat, filler cap and head gasket had been ruled out, and the pump appeared to be working because the water was obviuosly circulating, the only logical conclusion I could come up with was that there was a part blockage in the radiator which would not alow the water to circulate quick enough to cool at higher revs thus causing it to eqpand and blow out through the expansion bottle.

I tried a couple of bottles of rad flush and there was no difference so I bought a new rediator from Budget radiators on Ebay £69 delivered next day (excellent) and fitted it and there it was problem solved.

I hope this is of use to others who like me was scatching my head as to the problem.

P.s It's been fitted for several weeks and done a few k so it was definatly the fault and no more ear bashing from her indoors.

[RickT]

thanks for the update...

RickT

[hitachi]

Thought you guys were going to help me there ! I have similar problem water leaking from over flow on expasion bottle. when i undo radiator cap the water appears to come up the small pipe in to exp bottle with great pressure? which in turn tops up bottle again. I have changed thermostat & rad cap & bottle also done pressure test all to no avail. still loosing small amounts of water. Should there be that much pressure in the system. ps its a passat sport w regd

[Dave Avant]

Thought you guys were going to help me there ! I have similar problem water leaking from over flow on expasion bottle. when i undo radiator cap the water appears to come up the small pipe in to exp bottle with great pressure? which in turn tops up bottle again. I have changed thermostat & rad cap & bottle also done pressure test all to no avail. still loosing small amounts of water. Should there be that much pressure in the system. ps its a passat sport w regd

Yes the cooling system must be pressurised as water under pressure has a higher boilling point making it able to cope with high temps. When you take the cap off, which I pressume is when the engine is hot, the pressure is released and the coolant can expand and the only place it can expand to is the expansion tank.

How much are you topping it up with and how often. Some cars/engines will use some water between services etc. It depends to what extent. It may have a tiny leak that evaporates and is unoticable. Even with pressure testing it may not show up as sometimes it may only leak when the engine is hot or when its cold.

Also is the temp guage normal - does it warm steadily and then stay central?

[hitachi]

New radiator not helped, Done another pressure test today this time took car out for a drive with it attached pressure went off the gauge, ! so i guess its head off time. Is this an expensive job?

[beyerdynamic]

Hi All,

Just to keep everyone up to date, firstly thanks for you help and my appologies for the delay in keeping you updated with progress but I have been building an extention on my house, anyway I replaced the filler cap and that made no difference the car was still blowing out coolant when hot (i.e revs at a consant 3000 plus not at tickover) however the temp gauge remained at 90 deg and would only venture over after a long journey (50+miles) at "motorway" speedand after loosing a little coolent.

So bearing in mind that the thermostat, filler cap and head gasket had been ruled out, and the pump appeared to be working because the water was obviuosly circulating, the only logical conclusion I could come up with was that there was a part blockage in the radiator which would not alow the water to circulate quick enough to cool at higher revs thus causing it to eqpand and blow out through the expansion bottle.

I tried a couple of bottles of rad flush and there was no difference so I bought a new rediator from Budget radiators on Ebay £69 delivered next day (excellent) and fitted it and there it was problem solved.

I hope this is of use to others who like me was scatching my head as to the problem.

P.s It's been fitted for several weeks and done a few k so it was definatly the fault and no more ear bashing from her indoors.

Hi there,recently read your thread about your coolant probs with your a4 tdi.I have a similar prob. with my passat tdi 1997 r reg,can you tell me if you were getting pressure in the expansion tank when taking the cap off when the car was cold?,i too have ruled out head gasket i hope anyway,but was interested in your prob. with forcing water out of the tank at revs,look forward to a reply,many thanks.