coolant loss

[edoh]

odd one this....
dalek cap squeaks like a duck - hoses look fine and well clipped - coolant temp sensor renewed - coolant bled a la wiki - vw approved antifreeze in - up to the brim -
BUT - every week - losing about a tea cup size of coolant - and once a month - have to top up tank behind the number plate with about a pint of coolant/water mix - when the red temp light comes on and stays on -
then all fine again for another few weeks -
no oil mixed in with the coolant -
keep topping up - and looking at all the hoses - no obvious drips that i can see -
wondering where the coolants getting lost?
any ideas anyone?
as always - any thoughts appreciated

[CovKid]

Most common loss (perhaps) is not when the vehicle is out and about but when it stops after a run and cools down. Are you checking underneath at these times?

[itchyfeet]

Assuming pressure tank is full it's most likely a leak you haven't found.
Swapped my engine in summer and been loosing a little coolant since, just about found all the leaks 6 months later.

E D I T just read light coming on so pressures tank not full, worth a read

https://club8090.co.uk/forum/viewtopic.p ... 46&start=0" onclick="window.open(this.href);return false;

[edoh]

hey - thanks so much for the replies people
covkid - have only checked for leaks when van running - to see if i could identify where leak was - useful heads up to also check when van cooling down
itchyfeet - that's a really useful article - well worth bearing in mind -

further investigations required -
one more bleeding the system -
one more checking all the hoses when engine hot - and cold -
and see from there -

thanks again for the quick responses

[shepster]

Also, slight leaks can be burnt off as you drive along so difficult to trace.

I had a weep on the rad once but took ages to spot as it was burning away without dripping so didn't see it until I removed the grill.

[edoh]

Cheers
I was wondering if a small coolant leak could just be burning off on the exhaust or rad....

[Oldiebut goodie]

Heater valve? Not easy to see and often leaks unnoticed.

[Ralf85]

Have all the original main coolant pipes been replaced? One of mine was rusted through about 8 years ago. Assuming the pipes are in order, you've got a couple of dozen hose connections in the coolant system a few of them hidden away up front. After a drive the coolant is still under pressure. As pipes cool there is the possibility of this pressure finding a slightly loose hose and pushing a small amount out. Good luck searching.

[edoh]

hey - thanks again for all your contributions -
had a good look round when engine hot - and cold -
another bleed of the system - another check on all the hoses -
check on all the connections -
(where is the heater valve situated oldie? - any directions appreciated )
long drive - engine temperature as usual -
back home - leave engine to cool - a few hours later - check on coolant level -
pressure tank in engine bay (the one with the blue darlek cap) - still up to the brim!
YAY!
Then check the header tank (the one behind the number plate) - and half the tank is empty!
tried this whole routine one more time - bleed - top up - check hoses - drive - wait for engine to get stone cold - check coolant levels - pressure tank fine - header tank - half empty
hose between pressure tank and header tank looks fine -
wondering if it's time for a new header tank?

[AIR_CHILLED]

Hi,
How did you come to the conclusion you need a need header tank?
I need to change mine as I have hairline fractures in it that leak when cold but evaporate off when up to temperature.

Heater valve control is the in-cab control on the dash, this needs to be open (on hot) to allow any trapped air to pass through the heat exchanger.
If your expansion take is continuing to take inventory and you've got all the air out then you have a leak somewhere.
Get under the van with a powerful torch when cold and get familiar with the entire circuit.
It's a big volume, 17 odd litres I think so plenty of leak paths!
Look for signs of pink crusty coolant residue which evidently will burn off when warm.

I have a leak on the plastic flange to bleed rail on cylinder two just above the exhaust manifold, hard to spot that one as when hot all looked clean and leak free.

[Oldiebut goodie]

Heater valve is under the cab just to the right/in front of the gear lever behind the spare wheel. Poor diagram at 19.10 in Bentley

[kevtherev]

Then check the header tank (the one behind the number plate) - and half the tank is empty?

That's correct the top up tank (header tank) should not be full

[edoh]

thanks again for your contributions -
hairline cracks on header tank - not where the leak originates
all hoses and clips in engine bay look fine -
more looking required -
underneath and to the front!
thanks again to everyone -

[Oldiebut goodie]

If you look on the right of the tank you can just make out the max and min marks.

[MGP]

A pressure cap that is unable to hold the correct pressure but otherwise working would cause the same symptoms, check the level in the header tank when hot.
If you get stuck with this I'm happy to pop over with the pressure test equipment.

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