Cooling system pressurisation - any ideas as I’m stumped ATM?

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Geronimo
Posts: 5
Joined: Sat Mar 09, 2019 7:42 pm
Passat model: B7

Cooling system pressurisation - any ideas as I’m stumped ATM?

Post by Geronimo »

Evening all,

I’ve got a 2013 Passat Techmotion TDI 177 (it’s only done 131,000), which has a cooling system presurisation problem I can’t find the answer to.

I’ve done a hydrocarbon test (negative), replaced the thermostat assembly, done a system flush and replacement, changed the expansion tank, removed the fans to check the radiator front and back for any damage, checked all the pipes, clips etc. for leaks, blockage and can’t find any sign of a problem.

I’ve serviced it today so have had it in the air and looked at everything possible.

The heater matrix has a mind of its own and sometimes blows hot, then back to cold and then back to hot on all vent options. The lower radiator hose is solid after an initial run of about 20 minutes and then I have to release the pressure from the expansion tank to get things working properly and to top up as necessary.

There is no damp on the carpets, so there’s no ingress internally, so I’m stumped at the moment as to what could be causing this problem as all the normal things it points to I’ve addressed and checked or replaced, so if anyone has any ideas or suggestions, please can you let me know and I’ll keep searching to try and diagnose?

Where is the coolant possibly going?

Many thanks,

Jim

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