Oh dear.

Am loosing coolant but cant find where! Dealer said it was cap and replaced but still going down. 2.8 petrol. From the front it sometimes drips from right of undertray but when taken off cant see anything. Any ideas please?

Thanks

John

Best thing to do is get the engine running and up to temperature. It could be that the leak is only minor so doesn't show up when the system isn't pressurised, or is somewhere like the water pump or the return line that doesn't leak unless the coolant's circulating. With an undertray, the location of drips can be very misleading, unfortunately...

HTH

Does it leak a lot more when you put your foot down? ie after a motorway drive.

If yes, it could be a leaking head gasket resulting in increased pressure in the coolant system and the coolant expelled through the cap.

On 2.8 petrol it is easy to diagnose- ask mechanic to check for exhaust fumes in the coolant after a drive.

VAG radiators are rubbish and nearly always leak after about 5 years' use. It's usually very hard to see the leak until you pull the front - they normally fail at the bottom where the side pieces are crimped on. There are some very cheap Chinese radiators on eBay, but I would go for a Nissens radiator from GSF. I have found these to be generally better than the OE.

Whatever was a dealer doing replacing the cap without carrying out a pressure test? I hope you got your money back.

rotodiesel.

Many thanks for info. It does seem to use more if you go faster, but so far have not traced leak even tho its hot and running and no not got money back!!! Spent a few hours investigating???? and charged £65 + cap for the priviledge. Its going back to them!!

Not found anything 'oily' in header tank so far............

Many thanks for info. It does seem to use more if you go faster, but so far have not traced leak even tho its hot and running and no not got money back!!! Spent a few hours investigating???? and charged £65 + cap for the priviledge. Its going back to them!!

Not found anything 'oily' in header tank so far............

For stlg65 they've likely carried out pressure test. Successful pressure test again points to gasket and away from radiator (gasket leak initially only happens when you step on the accelerator). If they did not test, get it pressure tested and if there's a loss of pressure I agree the radiator is likely.

Does the temp gauge shoot forward after hard acceleration? E.g. after entering motorway at hspeed through an uphill entrance? This is faulty gasket trademark.

I had a similar problem had a test done, nothing but the water still disappeared. I think it was going into the oil. Bought a tin of leak repairer it is American stuff and it cured the problem instantly for a tenner.

I had a similar problem had a test done, nothing but the water still disappeared. I think it was going into the oil. Bought a tin of leak repairer it is American stuff and it cured the problem instantly for a tenner.

What did you use?

We sell both Bars Leaks and Radweld at Halfords, btw. Although I'd avoid the latter.

bars leaks I think!

Look around the hoses for a crusty buildup, this will indicate a leak as will streaking on the hose, I've one myself but until I'm ready to service it again I've left it.

Thanks for all the info. Temp gauge stays normal.It appears it may leak on cooling down - does that indicate anything? Infuriating thing is when you want it to happen it wont!!!!!!!!!!!!!

JJ

My TDI's head gasket timeline:

Early on: Temp gauge OK, coolant apparently lost on cooldown, but in fact it was evaporated/ejected under load, replaced by vapour and then went to a lower level on cooldown (when vapour condensed)

Later: Temp gauge overshot past 120deg C after entering motorway on uphill

So I'd recommend:

1. Look for the leak, it's not that hard to see (pinki-yellow residue)

2. If you cannot see the leak anywhere, keep driving for a while (and always make sure the coolant is there). Watch temp gauge 30s-60s after long acceleration (eg entering motorway). If it starts overshooting even a little, it's the gasket.

As I said earlier, best to test for exhaust fumes in the coolant, your mechanic should know how to do it.

Failing that, if you really want to diagnose it yourself, try adding K-seal (or similar). If it fixes the leak your problem is gone, if it does not fix the leak, it is almost certainly the gasket leak.

Note that if you find after adding radweld that your coolant got expelled in much larger quantity, again it's definitely exhaust entering the system and foaming the coolant (because of K-seal or radweld etc),