I have a problem guys and gals .i have a 2010 audi a3 170bhp diesel .my coolant is draining from the header tank but its not filling back up unless i go take the cap off ,then it gushes back in .no leaks either AA did a pressure check all good no leaks .i know sweet FA about cars .any help would be apperciated .

Sounds like an air lock in the cooling system. Given you know nothing about cars I suggest you take it to a garage.

3 hours ago, Chogger said:

I have a problem guys and gals .i have a 2010 audi a3 170bhp diesel .my coolant is draining from the header tank but its not filling back up unless i go take the cap off ,then it gushes back in .no leaks either AA did a pressure check all good no leaks .i know sweet FA about cars .any help would be apperciated .

Hi try changing the cap on the header tank as when they get old they leak air which centralises the pressure in the tank with the outside barometric pressure, the system is designed inside to work with a different barometric pressure to stop it boiling.

Steve.

In the past six months i have replaced header tank ,water pump intercooler radiator .today i watched it drained ,then i got my coolant warning ,i pulled over it was empty .i undid the cap it refilled instantly ,i got home took cap off again while coolant was still in then fast idled with everything turned on heater etc it drained in about 20 mins and never came back lol i looked under car no visible leaks so i topped it up again .once the engine was up to temp again i left the lid off and the coolant was just overflowing the neck  it seemed to burp lol and the coolant level dropped but then slowly rose again until it burped a few more bubbles .it sounds like its under a lot of pressure when it rus hees back into tank .im probs not making sense lol but i can only frscribe it as i see it i have no technical terms .

 

Ive recently lost my job so garage is a no go for me .

37 minutes ago, Chogger said:

Ive recently lost my job so garage is a no go for me .

Hi I am truly sorry to hear about the work situation, from your description I can only assume one of two things, its either the thermostat is on its way out or its the head gasket, my money is on the thermostat as you say its been pressure tested that should show up any gasket leaks but the thermostat would not, my neighbour was told her head gasket was blown but I took a an educated flyer at it and changed the thermostat and all coolant loss ceased, I only mention this as its very much cheaper than a head gasket leak which would blow the the water out in about five mins rather than twenty.

Steve.

Its funny you should mention that ,in the begining my heaters  were not getting hot luke warm but not hot .so i went and bought a thermostat BUT its not been fitted yet .would that cause the coolant to dissapear and the come back then .and thankyou btw 

11 hours ago, Chogger said:

Its funny you should mention that ,in the begining my heaters  were not getting hot luke warm but not hot .so i went and bought a thermostat BUT its not been fitted yet .would that cause the coolant to dissapear and the come back then .and thankyou btw 

Sorry to hear of your situation. Hope you find a job soon 🙂 I'm with Steve on this one and I'd definitely fit the thermostat to see if that cures the issues. 

Whoop whoop,so ive managed as a pure novice to strip out the centre console so i could gain access to the heater matrix as i suspected this may be blocked .nothing leaked from it weirdly it was bone dry (red flag)i put a new one in and now i have no coolant warning lights yaaaay no rushback into header tank nothing ,APART FROM NO FUXXXNG heating lol i never had it in begining to be fair ,thats what this whole quest started from ffs .the only thing thats not been changed yet is the thermostat which im aiming to do this week as soon as ive you tubed it hahaha another first for me .i would like to thank everybody that has replied and gave me guidance 🙏

Edited May 10, 20224 yr by Chogger

I thought it was an air lock when you first raised the matter. Your report of a dry heater matrix only confirms my opinion. It is a common problem after any work on the cooling system that involves draining any of the coolant.

There are several methods posted on-line to deal with air locks which can be difficult to shift from the A3, though I admit I have not tried them myself.

Is this an airlock

 

Airlock methinks