1.5L of coolant lost, no obvious leaks. Where has it gone?!

[M1ke]

Hi,

Over the past 2 days I have driven less than 10 miles and had to top up a total of 1.5L of coolant. The engine doesn't seem to heat up fully suggesting a stuck open thermostat but where is the coolant disappearing to? I drove 1 mile today and the radiator fan stayed on for ages after I turned the engine off (I topped up the coolant before setting off and it lost about 1 inch from the tank).

If anyone has any ideas beyond replacing the thermostat I'm all ears!

Cheers,
Mike

 

[S4_dan]

What engine do you have?

I was losing coolant a lot after my 13 mile journey to work. Replaced the thermostat and CTS as the temp gauge rarely moved and when it did, it was fluctuating.

Turned out my water pump impeller was slipping on the spindle. New water pump fitted and all is good now.

Mine is a 1.9tdi AWX.

 

[M1ke]

2012 A6 2.0TDI. It's done 80k. I'll get the pump replaced and see where it is, thanks.

 

[SootySport]

No good just changing the pump willy nilly, it's within the cambelt drive so a new cambelt needed as well. You need to ask this question in the A6 forum and you'll get more appropriate ideas when the coolant is going.

 

[S4_dan]

Yeah, as above, don't just change the pump without investigating first. I traced my fault to the pump and I changed it all myself. I didn't do the timing belt as that was done by a VW Dealer not too long ago but the pump wasn't.