Thermostat stuck open?

[Prof Mat]

Hi all,

I am almost certain that a thermostat stuck open is the issue here - temp fluctuates between 70 - rarely to 90 and temp drops and stays low when at speed or it is cold...

But just before buying parts and taking the spanners out, I wanted to double check:

1 - if others with a 3.2 petrol see temp holding steadily at 90 once warm (and that this temp fluctuation is not some weird idiosyncrasy of the 3.2 engine)

2 - the engine's done 100K - if others think thermostat failure at this age is not uncommon

3 - if I have got the wrong end of the stick and its actually something else

4 - I'll change the water pump while at it - anything else to change while the front etc is off (I did the aux belt and tensioner and pulley not long ago)

5 - what about carbon cleaning (assuming its been running rich for a while)?

 

Any replies appreciated.

M

[Steve Q]

Does sound like a thermostat. You could always do a diagnostic check to see if any fault codes flag up. You're doing the right thing changing the water pump. I've not head of the 3.2 fluctuating in temp 

[Prof Mat]

Great - thanks Steve. Helpful...👍

[Steve Q]

No probs

[Magnet]

Hello Mat,

Sounds almost certain to be thermostat issues. 
Couple of points:- what make thermostat are you intending to replace it with? 
Is the water pump leaking or noisy? If not, why change it? Again, if yay are intent on changing it, what make are you going to buy? 
Kind regards,

Gareth. 

[Prof Mat]

Thanks Gareth, appreciate your reply ... I always play the game of looking around for parts and toying with getting cheaper non-genuine, but end up deciding that getting genuine is usually (but not always) worth it. I've just rang Lincoln Audi to see what they want, and its £76 for the thermostat and £116 for the pump... genuine on eBay is no cheaper (versus stat for £35 and pump for £40 for Meyle). I figure a difference of £120 is worth it this time (I will easily save that by not having to pay garage labour).  I take your point with if it ain't broke why fix it on the pump (as this usually ends up creating other problems), but I think coolant pumps are the kinds of things it pays to replace (no evidence of ever being replaced before I got it a couple years ago) - I'll do the coolant temp sender as well for £30. Sods law some other cooling part will go once I do all that though...  still, stops me getting board...

best

M

[Magnet]

Hello Mat,

I applaud your principle of spending wisely on quality parts, since you aren’t paying any labour bills. 
I still question the reasoning behind changing the water pump, since genuine ones can be long lived. 
Genuine VAG parts mail order at discount?
Might be worth trying Audi Parts Direct at Cardiff ( part of Mon Motors/Cardiff Audi as was), and/or Aberdeen Audi - both are usually accommodating with a bit of discount. 
Kind regards,

Gareth. 

[Prof Mat]

Thanks Gareth,

Yes - probably overkill to do the pump but it nearly has to come out to change the thermostat (following workshop manual), and I have a tendency to belt and braces... thanks for the heads-up about Cardiff and Aberdeen... Lincoln Audi were accommodating with a little discount (possibly due to a sympathetic 2007 A4 Q owner on the parts desk 👍).

Oh - check codes as per Steve's Q: P2181 - 'engine coolant temperature mapping is lower and out of expected range based on operating conditions of the engine' - makes sense.

 

Another Q: ever used or heard of some who has used: http://www.enginecarbonclean.com/our-uk-pricing/

£100 seems good assuming it actually removes any carbon...

Best

M

[Sammyrai]

I just received my car yesterday having changed a stick thermostat (same symptoms as you). It's running perfectly now.

My car is only a humble 2.0TFSI, the genuine VAG stat cost £48, plus 1 hour labour.

I had the car serviced at the same time, and just need to take it out for a good long fun run!

 

 

[Magnet]

Many thanks for the helpful information Sammy.

Kind regards,

Gareth. 

[Prof Mat]

Yes - thanks Sammy - appreciate your response. Glad yours is sorted now