Overheating - Water pump issues

[guyg]

I have recently seen a lot of threads regarding overheating problems that seem to stem from faulty water pumps, so I thought this might be worth making into a 'sticky'

The water pumps an many of the VAG engines are fitted with a plastic impeller to avoid corrosion. Unfortunately, the plastic part has a habit of becoming loose on the shaft. When this happens, it spins lazily or not at all and there is little or no circulation. Sometimes, the impeller breaks up altogether.

The symptoms will be as follows:-
From cold, the temperature will rise and usually stabilise at normal running temperature for a very short time. The temperature will then start to climb again until the engine is stopped. [If there is absolutely no pause around 90C, then try changing the thermostat, but these rarely fail closed].

There will be no observable coolant flow in the header tank [although this is not conclusive on it's own].

There will be no coolant loss unless the engine was allowed to become hot enough to boil the coolant, in which case some will be lost via the pressure relief.

There will be little [if any] output from the heater and the rad fan will come on with little effect.

These are a pain to change, so if you're having a cam belt change, as a bit of PM, it's probably worth changing the water pump at the same time [they're around £30] especially on the A4/Passat/Superb where the front of the car has to be dismantled to gain access.

Hope this helps...

Cheers

Guy

[Cambrai]

Cheers Guy,
The symptoms you have described appear the same as my problem. I have been quoted £185 for replacement from Specialist Vehicles at Plympton in Plymouth. Is this a good price?
I appreciate the post to explain the potential problem.

Cheers Steve

[guyg]

Could be worse... this is much less that it would cost for the Passat; I'm guessing there's much more room in the new A6 engine bay - this was certainly the case with my old [1995] A6, so it looks like the front doesn't have to come off.

If you're anywhere near a cam belt change, it's proabbly worth having that done at the same time...

Cheers

Guy

[MalcQV]

This happened to my Pasty, all the symptoms as described, fortunately all corrected under warranty. I also had the cambelt changed whilst they did this and consequently it was quite cheap to do;)

This is a problem with a few cars now as they seem to be using plastic impellers in increasing numbers.

[Cambrai]

Hi Guy,
Got the waterpump changed the old one was in a terrible state just about functioning on life support!! Car runs fine now. Once again thanks for the advice as the garage could not find the problem initially as it wouldn't overheat under diagnosis and I gave them your advice.
Regards Steve
:beerchug:

[MalcQV]

Glad you got it sorted :approve:

[supa_greg]

Can someone tell me how much it is likely to cost me?? my TT has just started overheating and i have been told its the water pump. My car has only done 46k and i have been advised it may be a worse problem...! can anyone please shed some light on the situation?? Many thanks...

[Fred Thornton]

I drive a 2004 A6 2.0 petrol engine with 145k on the clock.

My water pump has just disintegrated, nothing left of the impellor. the shaft ceased and then twisted as the cambelt was still turning. luckily the escaping water reduced the friction on the belt making quite a strange high pitched noise so I turned the egine off straight away.

If they chose to use a plastic impellor because they don't corrode, surely they should last longer? or is this normal wear and tear?

PS: It cost me £ 700 to fix which included new water pump, timimng belt kit, timing belt hydraulic damper and auxillary belt guide pulley. And it happened only a week after I got the car back from having the CVT ECU replaced. Ouch.