What temp does the water pump start?

a3oz

Registered User
I pulled the engine out and put it back into my A3 about 6 months ago. At the time, I went over possible future failures and the water pump intake had some cracks (it had had a front impact) as something had struck it. So I bought a new one and replaced it. I have had a devil of a time sourcing the Xenon lights & all related kit but now have everything back together and doing short test drives.

There have been no water leaks with the front end all back on, but now after idling for a few minutes, as the water temp comes up just past the first 1/4 mark (the mark at a 45 degree angle), there is a 'popping' noise that starts. Had me stumped for a while but I'm now thinking that this is the water pump kicking in and either not mounting properly, or possibly cavitating(?) I just refilled the coolant from the top and stop/started until the coolant level stabilised.

Would appreciate any thoughts. The sound seems to at the front of the engine.
 

paddy

Registered User
Pump runs all the time but thermostat opens at about 85c you could have an air lock (popping noise)
 

a3oz

Registered User
I think you're right Paddy. I started the car when cold, set all the temp controls to HI and turned the fan on full. The engine warmed up (although not quite to 90C) and no more popping noise. I have the VCDS dongle on order now and once that arrives, I should be able to track exactly when the engine reaches 85C/the thermostat opens and see if it occurs at that point.
 
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