Coolant leak

[vwgolfv5]

I have a very annoying water coolant leak. There are no visible signs from where the leak is and my oil is clear of all signs from a head gasket.
When I had my anti freeze replaced a few months back, I asked the mechanic to give it a quick once over and he too could not see any signs of a leak.
But yet, at least once a week, my warning bleeper tells me that the expansion tank has dropped below the sensor and I have to top it up.

So, where is the water going ? and how can I fix it ?

[viperjsy]

try changing the expansion tank my dash light came on and it was the tank that needed replacing

[hardmonkeys]

On my mk4 it was the radiator that was leaking..very slowly.

Replaced,and all was ok

[vwgolfv5]

Thanks guys.
I will triple check the radiator. I don't think it is the expansion tank, it is too clean around that area, no signs at all of any leaks.

[Dalo Harkin]

If there are no physical signs of a leak anywhere then it must be being burnt in the engine.
if there is no powdery white/pink (depending on colour of antifreeze) anywhere then it must be being burnt

[WadGTI]

Might be worthwhile letting idle at 90 for 15 mins or so, check for any leaks, give a wee rev now and then, move the car and see if there is any leakage.

[barrym381]

Might be worthwhile letting idle at 90 for 15 mins or so, check for any leaks, give a wee rev now and then, move the car and see if there is any leakage.

what good will this do 

[james2]

Might be worthwhile letting idle at 90 for 15 mins or so, check for any leaks, give a wee rev now and then, move the car and see if there is any leakage.

This ^
Mine has had 3 pin hole leaks on the same metal pipe, it would only leak when the engine was hot. Also turn it off once its at 90 and remove the coolant bottle top (slowly). Should help it leak faster. 

[WadGTI]

Might be worthwhile letting idle at 90 for 15 mins or so, check for any leaks, give a wee rev now and then, move the car and see if there is any leakage.

what good will this do 

Its a better suggestion than the one you provided to the op 

And to answer your question Barry, I had a toyota , few years back, it had pin hole leak at the top of the rad on the hot liquid entry side which only really became visable when a) the stat opened fully taking the coolant bypass out of the equation and the coolant temp was up to 90 b, the water pump was turning higher that the idle tick over.

it might be a stupid suggestion in your view, but any suggestion is better than none in my view!

[barrym381]

Might be worthwhile letting idle at 90 for 15 mins or so, check for any leaks, give a wee rev now and then, move the car and see if there is any leakage.

what good will this do 

Its a better suggestion than the one you provided to the op 

And to answer your question Barry, I had a toyota , few years back, it had pin hole leak at the top of the rad on the hot liquid entry side which only really became visable when a) the stat opened fully taking the coolant bypass out of the equation and the coolant temp was up to 90 b, the water pump was turning higher that the idle tick over.

it might be a stupid suggestion in your view, but any suggestion is better than none in my view!

oh how exciting you had a Toyota once    and if its taking a week for the coolant to drop below the sensor level I cant see 15mins making much difference