Thermostat ??

[Spock]

Evening chaps,

just had the cambelt and water pump done on my sons 2012 A3 8P 2.0 TDI . Mechanic said it took just over 4.5 LTRS  of Coolant and may have an airlock but have heat in the cabin . Drove it home with the heater on and temp reached 90 degrees then when sat in traffic with blower on the temp reduced to 75 degrees (not normal as it should maintain 90) got home checked the level and managed to squeeze in another half litre. Took the car out along the motorway a little later , car got up to 90 degrees , heater nice and warm , and again at traffic lights temp reduced. Got home , removed the coolant cap , no hiss , as it wasn’t pressurised , coolant Luke warm after indicating 90 and 20 miles of motorway driving ! No coolant loss this time . Could it be airlock ? If so how to get rid ? Or thermostat ? 
 

Thanks 

[Steve Q]

Sounds like a dodgy thermostat 

[Spock]

My thoughts also Steve . I’ve got exactly the same model car and had to replace my thermostat last year . Pig of a job !!

[cliffcoggin]

I would expect 20 miles of motorway driving without full coolant flow to get it boiling, yet you say the coolant was only warm and there was no excessive pressure. That, together with the odd temperature reading, suggests to me there is still an airlock, probably in the heater matrix. A3s are prone to them and can be difficult to get rid of after opening the cooling system. I know of no certain way to eliminate the air as I have never needed to do mine, but I suspect that moderate vacuum would expand the air enough for it to bubble up to the reservoir.

[Spock]

I’ll let you know the outcome chaps . Thanks for the input 

 

Andy 

[Steve Q]

You're welcome, please keep us posted on how you get on 

[alpha omega]

mine was a pig of a job to do too on the audi a4 tdi maybe try what cliffcoggin thinks first regards stephen

[Spock]

It was the thermostat !! Thanks guys