Audi A3 cold air and losing coolant

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Flyingninja

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Hi everyone. I’m really hoping someone could guide me on my AUDI A3 issues. Car is Audi A3 2L diesel

About 1 month ago, whilst driving on the motorway, I noticed cold air blowing through the vents, I never thought much about it and drove home. The next day I got a message saying my coolant was empty. When I tried to open the coolant reservoir cap it was extremely difficult but I managed to open it and add coolant. After the incident I was constantly checking the coolant and got the reservoir bottle replaced.

I noticed that whilst driving locally my vents would blow warmish air (passenger side was slightly cooler then drivers), on the motorway after 15/20 minutes the vents would just blow cold air. Also whilst driving local/motorway the coolant would remain consistent but would go slightly lower the next day (after the car cooled down). Recently whilst driving I smelt coolant and saw white steam/smoke coming out near the residue (car overpressurised?). Again the reservoir cap was extremely difficult to open - I think the steam is melting something.

I’ve spend £200 taking my vehicles to two separate mechanics, both have said nothing is wrong with my car having looked at it under the ramp. I spoke with another mechanic who said I need to replace the water pump. He mentioned the car has three electric water pumps which work locally but on the motorway some ‘sleeve’ is unable to rotate the water pump resulting in cold air. He mentioned it won’t be the heater matrix as if the heater matrix is blocked then it would only give cold air and not hot air when driving local and cold air on the motorway.

Also the fan on the vehicle is constantly on when I drive small local journeys. I suspect it may be the DPF regen but it could be the engine overheating.

Sorry for the long message, I just want my vehicle fixed.

Many thanks in advance
 
Your mechanic already told you to replace the waterpump... I suggest you listen to the man. The one that is causing the problem is the one driven by the timingbelt so best to have that replaced at the same time.
 
northpole said:
Your mechanic already told you to replace the waterpump... I suggest you listen to the man. The one that is causing the problem is the one driven by the timingbelt so best to have that replaced at the same time.
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Thanks for the reply, everything I read on the forum suggests it's the heater matrix. Just want to get other peoples views before proceeding with it.
 
No it's the waterpump a blocked heatermatrix can easily be ruled out by using a piece of pipe to bypass it. But since it happens on long journeys and the expansion tank keeps overflowing yet pressure keeps building up it rules out the heatermatrix. Also the dead giveaway: the fans are on constantly... it means the flow is restricted, the electrical waterpumps still work giving enough flow for slow speeds but on constant speeds the mechanical waterpump does the heavy lifting. When it's broken internally it becomes a problem when doing motorway runs...

Longstory short replace the waterpump and timing while your at it.

Ps.scan the car and check if the thermostat isn't stuck closed as that can give the exact same symptoms
 
northpole said:
No it's the waterpump a blocked heatermatrix can easily be ruled out by using a piece of pipe to bypass it. But since it happens on long journeys and the expansion tank keeps overflowing yet pressure keeps building up it rules out the heatermatrix. Also the dead giveaway: the fans are on constantly... it means the flow is restricted, the electrical waterpumps still work giving enough flow for slow speeds but on constant speeds the mechanical waterpump does the heavy lifting. When it's broken internally it becomes a problem when doing motorway runs...

Longstory short replace the waterpump and timing while your at it.

Ps.scan the car and check if the thermostat isn't stuck closed as that can give the exact same symptoms
Click to expand...
Thank you very much, appreciate the response. Is there a reason why the coolant cap is keep getting stuck?
 
Yeah it's the pressure it builds up... because of the non responsive waterpump.. at first it'll push out the extra pressure through the vent hole.in the expansion tank... than when the coolant has dropped below minimum level it'll start pulling a vacuum... and in doing so, the cap gets very hard to remove.
 
northpole said:
Yeah it's the pressure it builds up... because of the non responsive waterpump.. at first it'll push out the extra pressure through the vent hole.in the expansion tank... than when the coolant has dropped below minimum level it'll start pulling a vacuum... and in doing so, the cap gets very hard to remove.
Click to expand...
Thank you!
 
Just a follow up, would you recommend I get a geuine Audi waterpump/timing kit or a aftermarket one. The mechanic suggested I get a aftermarket one since the genuine are prone to faults. I'm conflicted since I'm hesitant in putting a non genuine part in my vehicle
 
Just get the recommended stuff by your mechanic.. he actually is right on point.
 
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