Hi, new to the forum and bought my 2015 A7 Quattro 3.0tdi last August.

it was high miles at 100k but in good condition and was reflected in the low price.

I noticed low coolant in December and put in some before booking it in to a garage for check. The heater was cold and no warm air at all after topping up coolant it was warm again.

They diagnosed it for faults and found none. They pressure tested the system and found no leaks so was topped up and good to go.

Since getting it back started to notice a sweet smell and poor mpg. Checked coolant today as heater not hot and was almost gone!! Topped up and heater warm.

Temp is at 90 and never had any warning lights.

Any ideas? 

Hello Steve, 

Thanks for being in touch. 

It’s stating the obvious that coolant is being lost - either via. an external leak ( smell of coolant?) or via. being burnt as part of the combustion. 

If this were mine, I would be seeking out a good recommended local diesel specialist, and get them to check this over, and isolate the problem. 

Kind regards,

Gareth. 

There's no coolant leaking on ground and also the low coolant sensor has never lit up even though it's really low.

just wondered if there was something obvious other owners had seen.

I'll try another garage but the local Indy Audi guy is chocker and quoting weeks to look at it due to lockdown.

Thanks

Ok Steve - thanks. 

By what you tell us, the car is losing coolant even though you have not let that loss low enough to activate the low coolant sensor - you say ‘ almost gone’. It has to be going somewhere! 

What you don’t tell us is what mileage is covered for the coolant to drop to ‘almost gone’, from the starting point of being topped up - the Max. mark? 

Appreciating the Audi independent is booked up, but my suggestion was to get the car inspected by a diesel specialist rather than an Audi specialist. 

Kind regards,

Gareth. 

 

Update after the diesel mechanics tested the car. Cylinder Head Gasket compression tested ok. Water pump was leaking and has been replaced under the warranty. MPG back to normal, heaters working and no smell.

All working so thanks for the advice. 👍👍

Wondering if you ever found the root cause of this issue? I ask because I had a similar issue a few months back (2016 A7 272), it was diagnosed as a leaking coolant shut off valve (example here), it was replaced and a large wad of cash was given to Audi in return. Symptoms were loss of 1L of coolant every few weeks and a noticeable leak down the front of the engine near that main pully.