Sudden Overheating ...

[n0m1secnerwal]

Hi,

I have owned an A6 2.8 Quattro (1998 S Reg) for almost a year now. It's been reliable and fun to drive. It was a nice sunny day yesterday and after a short blast, I heard and saw the temperature warning. Luckily, I was just pulling up at home!

Turned heating right up, and opened the windows but temperature only increased. Switched off engine, waited for it too cool and topped up coolant which had escaped via the expansion tank overflow. Coolant bubbled up into expansion tank as pressure was released when undoing the filler cap - carefully! Checked oil level and topped up about 500ml.

Restarted engine, temperature guage was reading half way - normal engine running temperature. Temperature quickly started to climb even though heating on full whack!

I guess this is a new water pump! /ubbthreads/images/graemlins/frown.gif Is this a big job? Are water pumps expensive? Anyone able to give me instructions for changing the water pump?

Any advice would be gratefully received.

 

[maxlbrown]

FIrst try the thermostat these are classic symptoms its also a cheap replacement

Thermostat at about 8 pounds from GSF auto parts and water pump about 25

Max

 

[S4_dan]

also check your fans are kicking in. The sensor can sometimes get covered in cr@p or fail completely thus not turning the fans on. And it may of failed a while ago, but due to average weather etc the engine may not of reached the optimum temp to start the fans in the past.

Again, the thermostat is a classic failure, on most cars not just audi's.

sensor is approx 19 + vat from a stealer. I've just replaced both temp sensors on my S4. Works a treat now the fans do.

Good luck.

HTH

Dan

 

[n0m1secnerwal]

Yeah, you're right they are classic symptoms, points to no water circulation. I was just being pessimistic I suppose with the water pump.

I can't find the thermostat housing. it's probably in an obvious place, but I can't see it for looking! /ubbthreads/images/graemlins/wink.gif Anyone able to give me a clue? It's not behind the water pump is it?

Forgive my ignorance, this is the first 4 ring car I've owned.

Thanks for the response Max /ubbthreads/images/graemlins/bravo.gif The A6 board here seem's to be a bit quiet, or so it seems to me, so it is appreciated.

 

[n0m1secnerwal]

[ QUOTE ]
also check your fans are kicking in. The sensor can sometimes get covered in cr@p or fail completely thus not turning the fans on. And it may of failed a while ago, but due to average weather etc the engine may not of reached the optimum temp to start the fans in the past.

Again, the thermostat is a classic failure, on most cars not just audi's.

sensor is approx 19 + vat from a stealer. I've just replaced both temp sensors on my S4. Works a treat now the fans do.

Good luck.

HTH

Dan

[/ QUOTE ]

That's a fair point, however, the fan is on a viscous coupling and is therefore spinning all the time. So it's not that.

There is a "Creaking" type noise coming from the area of the water pump at idle. I put this down to loose drive belt originally. I can't see any water coming out of the water pump like in classic bearing failure though!

Thanks for the pointers /ubbthreads/images/graemlins/beerchug.gif. I'm hoping it's just a stuck thermostat. Just need to locate it.

 

[n0m1secnerwal]

Okay here goes ...

Firstly, there is an auxiliary fan (how could I have missed that!), not just the viscous coupled fan. This auxiliary fan is controlled by a switch on the radiator. Surprise surprise the switch was bust and caused the original problem!

There's a second sensor that feeds the ECU and the temperature gauge / audio-visual warning system. This was bust too!

When the sensors were replaced the auxiliary fan kicked in too late, by about 20 Degrees Celsius too late! All hoses were unbearably hot except the one fed from the thermostat.

Slightly sticky thermostat confirmed! Replaced water pump, which was just as well - impeller was about to drop off! Replaced cam belt, as it had to come off to get to thermostat housing.

All now fine and dandy.

 

[maxlbrown]

Blimey You had the lot! Well done and happy cool motoring

Max

 

[Fruit and VAG]

The impellars are prone to going.. of all the things that are great about German cars, they still make the water pumps with plastic impellars.... they could at least use carbon fibre but the labour charge on a water pump is huge for the manufacturers and you may as well do the cambelt while your at it.

I was quoted £1000+ for a new water pump Audi... I ended up getting a specialist to change it and the cambelt for £400 all in.

I recently had a major service with MOT for £300 all in... so I added a REVO remap on the top. A little extravagent seeing as it will go in about a year to make way for an S4.