Hello all, really hope you might be able to help with this . 

I have a n Octy 1.9 TDi pd and have real problems with the coolant system, as it is always pressurezed. 

It will show coolant level low , and when I when I release the exp tank cab it will return to normal. The cabin fan always blows out cold air when car up to temp.Even in the morning the tank holds pressure.

So far I have had the following replaced but to no avail....

Water pump

Thermostat

Expansion tank

Garage have done compression test ....All ok

Sniff test  also resulted ok

Garage does not think h/gasket gone , and car runs perfectly well.

 

Thanks in advance for any suggestions

1 hour ago, trc said:

Hello all, really hope you might be able to help with this . 

I have a n Octy 1.9 TDi pd and have real problems with the coolant system, as it is always pressurezed. 

It will show coolant level low , and when I when I release the exp tank cab it will return to normal. The cabin fan always blows out cold air when car up to temp.Even in the morning the tank holds pressure.

So far I have had the following replaced but to no avail....

Water pump

Thermostat

Expansion tank

Garage have done compression test ....All ok

Sniff test  also resulted ok

Garage does not think h/gasket gone , and car runs perfectly well.

 

Thanks in advance for any suggestions

All modern cars have pressurised cooling systems. Maybe you have a bad heater element?

Unlikely I think , because when I’m doing about 60 or so I get hot air . Can’t help thinking it might be an air lock in the system.

All modern cars do indeed have pressurised cooling systems when warm/hot, but as you don't have to pump them up after topping up the coolant or otherwise removing the cap, if there's pressure when the engine is stone cold, it strongly suggests that something additional has entered the cooling system. Usually combustion gases via 'head lift' on a 1.9 tdi, I believe. Only happens during high power operation, and may well be one-way, without coolant loss, at least initially.

Chemical testing (or even sniffing) of the expansion tank after a 'lively run' (with suitable cooling time to not injure yourself) may show the presence of combustion gases.

Edited 11 November, 20187 yr by Wino

Could very well be,it has crossed my mine. When going up hills the temp gauge overheats until I get to the top , and goes back to 90c. Running around time it sits on 90 c with no problems.