Overpressurising?coolant being pushed out of expansion bottle .

[Mike McKinstry]

Hi All-not posted for a while due to the old '09 140 Golf never having many issues. Its gone now so here we go..
For several months I have had an issue with 2014 A3 150hp 2.0TDi throwing all coolant out of the expansion tank after longer runs30miles+.
Running back/ forward to work 9 miles each way no apparent issues and coolant moves up a few mm in bottle however may feel warmer than our Passat on same journey.
Longer runs temp gauge always at 90 and no obvious signs of overheating .
One longer journey felt we heard bubbling from behind dash but not heard since on other incidents.

No work done previously apart from an aircon condenser 12 months prior

So to resolve-First garage returned car saying loose connection on aux water pump and all sorted. Issue continued.
I Sourced new expansion tank cap from GSF and fitted-no improvement.
Next garage as there was no obvious flow of water from pipe into expansion tank and cambelt was due anyway did waterpump and cambelt and have hopefully fitted non shroud type water pump.Also prior to change did a smoke test for HGF but ok. Garage also thought new cap not good fit so old cap replaced and advised to try car .At same time silica bag has been removed from bottle and no signs of any splits/damage.
Unfortunately issue continues and on recent 25 mile motorway trip heaters went cold which turn out to be result of all water thrown out of expansion tank again-through the vent.
Same garage now suggesting HGF but no signs of any coolant contamination or dipstick mayo and pipes dont get rock hard straight way on start up and in my gut Im wondering if a matrix change would sort the issue-do also think heater doesnt really pump hot air through like our passat or fiesta although friend with Golf R thinks the heather just not as good in the later models having to turn to 24 when maybe older version was 22.

Any thoughts on a way forward please as very frustrated, not using the car and having to tax and insure a spare vehicle due to the Audi being off road or unusable ..
Amazing to see Crasher still on here all these years!!!! Top Man.

[Crasher]

Yes, still here, a bit like an irritating rash you can't get rid of. I haven't done it but I have heard using the none variable displacement pump can cause problems and on certain engine such as the CUNA they are almost impossible to fully bleed with a vacuum filling system and a specific computer bleed process so around 2L of water volume air stays trapped inside the system and travels around causing hot spot boiling and overflow.

[Mike McKinstry]

Yes, still here, a bit like an irritating rash you can't get rid of. I haven't done it but I have heard using the none variable displacement pump can cause problems and on certain engine such as the CUNA they are almost impossible to fully bleed with a vacuum filling system and a specific computer bleed process so around 2L of water volume air stays trapped inside the system and travels around causing hot spot boiling and overflow.

Hi,
Thanks for reply.
Do you mean without a vacuum pump and computer bleed process hard to get rid of air or even with this process I could have airlock??

What would you suggest as a course to remedy this -apart from auctioning the car which is very tempting at the moment ?
So you dont believe heater then ?

[Crasher]

What is the VIN? The CUNA code engine is the worst for this.

[Mike McKinstry]

what is the vin? The cuna code engine is the worst for this.

wauzzz8v3ea170210
crbc191548

[Crasher]

Yes it has the system which is near impossible to bleed without ODIS and a vacuum system. I find even VCDS cannot initiate the bleed procedure ODIS can.

[Mike McKinstry]

Yes it has the system which is near impossible to bleed without ODIS and a vacuum system. I find even VCDS cannot initiate the bleed procedure ODIS can.

Oh Dear .Who would sort that then -dealer?
Not sure why I would even have an airlock as this happened before water pump changed etc
And everything had been fine up until first expansion tank dump of coolant .
Maybe when condenser changed g13 got mixed with something else ?
Still think heater matrix could be part of problem as heater vents don’t feel as hot as they should be (I feel) but even if I changed that the bleeding may mean I fail to resolve issue anyway .

Feel a trip to “we buy any car”may be the easiest solution to this problem and no more VAG for me

[Mike McKinstry]

[QUOTE=Mike McKinstry;1153574]Oh Dear .Who would sort that then -dealer?
Not sure why I would even have an airlock as this happened before water pump changed etc
And everything had been fine up until first expansion tank dump of coolant.
Still think heater matrix could be part of problem as heater vents don’t feel as hot as they should be (I feel) but even if I changed that the bleeding may mean I fail to resolve issue

[Mike McKinstry]

Ran car 40 miles today with heater off and had no loss of coolant from expansion tank vent which I would have expected .
Not sure the significance of this but will try again with heater on and see how long it takes for coolant to appear .

[Crasher]

Odd, maybe it has purged itself?