Coolant loss

[vw754]

Rs3 2019.
Coolant goes from max to minimum roughly every 200-300 miles , took under tray off no leaks , pressure tested , gauge on the pressure tester drops very slowly , a good 2 minutes+ before you notice gauge dropping , any ideas?
No smoke nothing unusual , doesn't over heat etc

 

[northpole]

check the expansion bottle for traces of coolant on the rear of it... there is a pressure release hole in it that might be pushing access pressure out... this usually is a sign of a bad working coolant bottle lid as they are made to release pressure... if they fail the expansion bottles pressure release hole is the backup... so you can continue driving... but that comes with loss of coolant overtime. so your first point of call will be to replace the expanion bottle lid/cap... if you've done that and it still happens... have the cooling system pressure tested.

 

[flybynite]

Rs3 2019. Coolant goes from max to minimum roughly every 200-300 miles , took under tray off no leaks , pressure tested , gauge on the pressure tester drops very slowly , a good 2 minutes+ before you notice gauge dropping , any ideas?
No smoke nothing unusual , doesn't over heat etc

First thought is water pump, as it is a known problem and you are not likely to see a leak this time of year as IIRC it only leaks when driving.

I would also keep an eye on the oil cap to check for mayonnaise as head gasket, although unlikely is not completely unknown

 

[vw754]

check the expansion bottle for traces of coolant on the rear of it... there is a pressure release hole in it that might be pushing access pressure out... this usually is a sign of a bad working coolant bottle lid as they are made to release pressure... if they fail the expansion bottles pressure release hole is the backup... so you can continue driving... but that comes with loss of coolant overtime. so your first point of call will be to replace the expanion bottle lid/cap... if you've done that and it still happens... have the cooling system pressure tested.

THanks

 

[vw754]

First thought is water pump, as it is a known problem and you are not likely to see a leak this time of year as IIRC it only leaks when driving.

I would also keep an eye on the oil cap to check for mayonnaise as head gasket, although unlikely is not completely unknown

Ok thanks , bit of mayonnaise on the oil cap yesterday when I was doing a oil change , but saying that car had been driven first time after sitting for a week or so

 

[flybynite]

Ok thanks , bit of mayonnaise on the oil cap yesterday when I was doing a oil change , but saying that car had been driven first time after sitting for a week or so

In which case I would get a compression and leak-down test. Mine (albeit a DAZA) sits for much longer than that and cap is (so far) clean as a whistle.

 

[vw754]

In which case I would get a compression and leak-down test. Mine (albeit a DAZA) sits for much longer than that and cap is (so far) clean as a whistle.

Will be doing a 130 miles round trip later today , will check cap before I set off and check it again tomorrow morning see if it's clean or not

 

[vw754]

Cap was clean before I set off today , drove round trip of around 130-140 miles , checked oil cap , all good , nice and clean , smelt coolant , checked under the bonnet and noticed these 2 if any has an idea , pipe that I've circled was wet , and at the bottom of the rad , just below the pipe...damp patch.

 

[northpole]

looks like you got a leaking radiator... I'd replace it asap, because if left it'll get worse a lot quicker than you'd expect. refrain from using a stop leak solution... it can make matters worse ( like blocking the interior heater matrix's core)

 

[vw754]

looks like you got a leaking radiator... I'd replace it asap, because if left it'll get worse a lot quicker than you'd expect. refrain from using a stop leak solution... it can make matters worse ( like blocking the interior heater matrix's core)

Will double check it's the rad and not the pipe , cars got extended warranty anyway

 

[HM3P]

Cap was clean before I set off today , drove round trip of around 130-140 miles , checked oil cap , all good , nice and clean , smelt coolant , checked under the bonnet and noticed these 2 if any has an idea , pipe that I've circled was wet , and at the bottom of the rad , just below the pipe...damp patch.

Check around this pulley for the water pump.
It can leave evidence if weeping

 

[vw754]

Check around this pulley for the water pump.
It can leave evidence if weeping

View attachment 282836

Had it on the ramp on Saturday did oil change couldn't see any coolant residue anywhere ,will look again at some point