Audi A3 8V 2.0 TDI coolant loss and intermittent heat in cabin

[serrobert]

Good morning everyone, I'm looking for a possible solution to a recent problem I'm having with my A3.

It's a 2014 8V 2.0 TDI currently sitting at 163.000 km / 101.000 miles. Recently I noticed the coolant level not being consistent and no heat when using a/c.

I topped up the coolant to the "max" line (car cold) before a long trip I had to take (500 km / 310 miles). The next day (car cold again) the coolant was again under the "min" line.

Car was running fine the whole trip, without overheating with oil temperature in the 98-103 °C range (208-217 F). No heat in cabin the whole time.

I recently serviced the car and replaced diesel, air and oil filters, along with a full change of oil. Old oil was clean black and not contaminated - I'd exclude a failing head gasket.
Aircon controls works fine and putting it on max blasts cold air at full force.

Yesterday I suddendly had hot air again. Stopped for some errands, coming back no hot air again.

Once home I checked the engine bay for the coolant level and saw a lot of coolant in the engine bay, directly under the container.

 

I'll inspect it for cracking or leakage, but could it be linked to the missing heating or it's probably the heater core matrix too?

[Steve Q]

I'd have said heater matrix as the first port of call. Have you got any wet carpets which could be caused by a leaking matrix? 

Definitely inspect the expansion tank as these can split especially around where they're joined together. I had that on a works van late last year. 

[serrobert]

Thanks for the answer, no wet carpets around driver nor passenger side. Still have to inspect the expansion tank, wife drove the car (no signs of overheating luckily) and it was still pretty hot.

That's the situation under the expansion tank.

My idea is that the heater core is clogged / partially clogged resulting in an increased pressure in the cooling system. 

Edited January 13, 2023 by serrobert

[Steve Q]

Hmm interesting. Might be worth getting the system flushed first for sure. 

[Magnet]

Hello Robert,

If not obvious leak site around the expansion tank, then it might be worth try a new quality replacement cap. 
Kind regards,

Gareth. 

[serrobert]

Update for whoever finds this thread in future.

Apparently my expansion tank is a different revision and has no physical silica bag inside. So no burst silica bag. Also checked with VCDS for errors but aircon unit had no faults.

I ordered an original Valeo heater matrix from Germany for less than 100€, disassembled the entire central tunnel and replaced it.

No leaks around the AC site, but the old heater matrix was almost 100% blocked. After cleaning it I tried to blow inside but only very little air was coming out. Compared to the new it was day and night.

Reassembled everything, refilled the lost coolant, reset all the errors.

Aircon works again, even hotter than before. After another small trip of 1000 km coolant level seems to be stable. Will keep an eye on it in the next weeks.

Edited January 30, 2023 by serrobert

[Steve Q]

53 minutes ago, serrobert said:

Update for whoever finds this thread in future.

Apparently my expansion tank is a different revision and has no physical silica bag inside. So no burst silica bag. Also checked with VCDS for errors but aircon unit had no faults.

I ordered an original Valeo heater matrix from Germany for less than 100€, disassembled the entire central tunnel and replaced it.

No leaks around the AC site, but the old heater matrix was almost 100% blocked. After cleaning it I tried to blow inside but only very little air was coming out. Compared to the new it was day and night.

Reassembled everything, refilled the lost coolant, reset all the errors.

Aircon works again, even hotter than before. After another small trip of 1000 km coolant level seems to be stable. Will keep an eye on it in the next weeks.

Glad you got sorted 🙂

[Toni123]

On 1/30/2023 at 10:56 AM, serrobert said:

Update for whoever finds this thread in future.

Apparently my expansion tank is a different revision and has no physical silica bag inside. So no burst silica bag. Also checked with VCDS for errors but aircon unit had no faults.

I ordered an original Valeo heater matrix from Germany for less than 100€, disassembled the entire central tunnel and replaced it.

No leaks around the AC site, but the old heater matrix was almost 100% blocked. After cleaning it I tried to blow inside but only very little air was coming out. Compared to the new it was day and night.

Reassembled everything, refilled the lost coolant, reset all the errors.

Aircon works again, even hotter than before. After another small trip of 1000 km coolant level seems to be stable. Will keep an eye on it in the next weeks.

Hi Thanks for the update, very useful thread.

I have a Audi A3 2016 2.0 TDI and have a similar, I really could do with some advice please.

For the last 6 months or longer, I have had only a warmish air coming thru the heaters, I noticed when driving on the motorway, it does get a bit warmer, but most days it's cold. 

I've also noticed there's coolant coming out of the side vessel of the expansion tank, I believe its spraying out due to the high pressure, also sometimes I can hear a gurgling/ steam noise when in the car. The coolant is very clear and the the engine oil has no cream.

I have recently taken the car to a VW specialist and they believe it's due to a clogged heater matrix, which I plan on changing myself this week.

 Could the clogged heater matrix be causing the high pressure in the expansion tank?

 

Thanks

[Stevey Y]

5 hours ago, Toni123 said:

Hi Thanks for the update, very useful thread.

I have a Audi A3 2016 2.0 TDI and have a similar, I really could do with some advice please.

For the last 6 months or longer, I have had only a warmish air coming thru the heaters, I noticed when driving on the motorway, it does get a bit warmer, but most days it's cold. 

I've also noticed there's coolant coming out of the side vessel of the expansion tank, I believe its spraying out due to the high pressure, also sometimes I can hear a gurgling/ steam noise when in the car. The coolant is very clear and the the engine oil has no cream.

I have recently taken the car to a VW specialist and they believe it's due to a clogged heater matrix, which I plan on changing myself this week.

 Could the clogged heater matrix be causing the high pressure in the expansion tank?

 

Thanks

Hi yes the matrix would cause this as the heater is fed from a bypass before the thermostat so the car gets warm air quickly from starting, think I remember reading that the way the system is designed it is prone to clogging as it is not high pressure enough to clear naturally occurring debris in the water system, would also suggest a new expansion tank while your at it.