HELP - Overheating 2005 A6 4.2 V8

**jpbeng** · 20-01-2011,01:14 PM

Hi
I have a 2005 A6 4.2 V8 Quattro S Line.
It will run and idle fine all day long with the temp staying at 90 and fans kicking in and out, as soon as you drive it (and especially when using the paddle shift) the water temp shoots up to 135, the water in the header bottle boils over and it losses most of its coolant out of the header bottle overflow.
There are no warning lights at any point other than a coolant level warning light after the event.
I have pressure checked the system and it was good. The oil seems clear of water and visaversa.
Would I be right to think along the lines of a sticking thermostat or the waterpump (does this use a plastic impeller?)?
Also have you any idea where these are and how easy/hard a job they are?
Should I use genuine Audi parts or are GSF or Euro ok?
Many thanks

**kite** · 20-01-2011,01:53 PM

OEM parts, they come with a 2yr warranty.
I would suspect the water pump,

**iwaters** · 20-01-2011,02:15 PM

Originally Posted by kite

OEM parts, they come with a 2yr warranty.
I would suspect the water pump,

Only if they are fitted by a mechanic. If you DIY it you only get a year. You should still use the genuine parts which ever route you take.

Could be either the pump or the stat. You could remove the stat and test it but it costs about £40 whereas it will take quite a bit of labour to get to it. Might as well strip and replace both including the timing belt and tensioners unless they are very new.

**kite** · 20-01-2011,02:18 PM

Originally Posted by iwaters

Only if they are fitted by a mechanic. If you DIY it you only get a year. You should still use the genuine parts which ever route you take.

Could be either the pump or the stat. You could remove the stat and test it but it costs about £40 whereas it will take quite a bit of labour to get to it. Might as well strip and replace both including the timing belt and tensioners unless they are very new.

Well, you learn something every day...thanks.

**Peter D** · 20-01-2011,03:26 PM

I too suspect the water pump. Access means the front has to go into the service position but the water pump is driven by a drive shaft from the back of the oil pump. I suspect the engine is a BAT or BNK neither of which have a timing belt. It has a complex set of timing chains at the rear of the engine. I would also change the stat as it has been well strained at 135 degrees. The pump and stat are part of the same unit, lower right front of engine with a cluster of houses. Regards Peter

**jpbeng** · 20-01-2011,04:24 PM

Thanks for the replies everyone.

I have looked into it a bit more myself this morning at the local Audi dealers.
It is a BAT engine, so on chains not belts.
Water pump and stat are in a remote housing off the engine as you have said.
On Audi's diagram for the car it looks as though it is driven by a pulley which comes of the Vee belt?
It means the front end of the car coming off to access it. Nice!
Audi dealer has quoted 5.2 hrs labour at £85/hr, £140+VAT for a water pump/thermostat kit.
Needless to say, it's going to my local garage at £30/hr, but having genuine parts fitted!

Thanks again

**Peter D** · 20-01-2011,04:45 PM

It is not remote, and not belt driven. It is fixed to the front of the engine and a small drive shaft sticks out from the front of the oil pump through the engine housing. The Aux belt drives the alternator, the steering and A/C are shaft driven which are driven fron one of the chains at the rear of the engine. If you PM me your email I'll send you the drawings. Regards Peter