Coolant smell and no aux heater

**PerArdua** · 20-12-2021,04:14 PM

Since my last service in October the coolant level has dropped very slightly (from max to just under min) but after a slow run in town you can definately smell coolant but nothing apparent in the engine bay or around the hoses and the loss is very small. At the same time the aux heater has stopped working, could the two issues be connected? 2015 A6 Allroad 3.0 272bhp

**Crasher** · 20-12-2021,07:46 PM

In standard form the aux heater is a Positive Temperature Coefficient (PTC) electric element so should be unconnected with a coolant leak, start with a code read of the HVAC.

**Noony** · 21-12-2021,09:15 AM

The smell of coolant, inside the vehicle, is usually the heater matrix.

**PerArdua** · 21-12-2021,11:44 AM

Originally Posted by Noony

The smell of coolant, inside the vehicle, is usually the heater matrix.

No smell inside the car, just outside when you get back you can smell it. I am wondering if the expansion bottle is leaking as that happened with one of my Passats.

**gav28uk** · 21-12-2021,12:56 PM

I had the same, smell of coolant, have a look through and into the bottom of the engine, see if there is a nice puddle forming. I hope it's not what I had! I had a leaking thermostat housing (apparently a well know issue in the 3.0 v6) and a leaking coolant regulating valve in the bottom of the V, big expense, nearly £1k as it involved strip and rebuild plus replacing lots of gaskets/seals during the rebuild. And that was with an independant.

**PerArdua** · 21-12-2021,01:19 PM

Originally Posted by gav28uk

I had the same, smell of coolant, have a look through and into the bottom of the engine, see if there is a nice puddle forming. I hope it's not what I had! I had a leaking thermostat housing (apparently a well know issue in the 3.0 v6) and a leaking coolant regulating valve in the bottom of the V, big expense, nearly £1k as it involved strip and rebuild plus replacing lots of gaskets/seals during the rebuild. And that was with an independant.

Car is under warranty so I will need to get it looked at, what diagnosis did they do to find the leak? I seem to losing so little I doubt I am getting a puddle but will have a look, thanks

**gav28uk** · 21-12-2021,01:30 PM

They were Audi specialists and seem to know that the Thermostat housing would be the likely problem, apparently made of plastic which becomes brittle in the hottest part of the engine. They said they couldn't be 100% certain until they reached the Thermostat housing, but when they did, it was confirmed. They then found another smaller leak from the coolant regulating valve whilst doing the work. My coolant levels went from max to min over the spate of 6 months or so. I topped it up and then it was fine for months, then started dropping again. It was at that point I had it checked. Glad you have it covered under warranty...no need to worry at al then, hand it over and let them get on with it.

**Crasher** · 21-12-2021,05:39 PM

The regulator valve when it leaks tends to cause coolant to run over the oil pressure control valve on the front of the engine and leave pink stains. It takes my spanners a full day to change the coolant reg valve in the V. The coolant stains don't show up in this pic

**Noony** · 24-12-2021,09:35 AM

My apologies I didn't read your original post properly.

**PerArdua** · 24-01-2022,02:28 PM

Originally Posted by Crasher

In standard form the aux heater is a Positive Temperature Coefficient (PTC) electric element so should be unconnected with a coolant leak, start with a code read of the HVAC.

Just heard from garage that no codes being thrown up, just wondering if the heater can fail 'safe'? It is going to be cold started tomorrow to check further