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Matt, Engineer
Category: Audi
Satisfied Customers: 20374
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Audi A7: My A7 giving me a "coolant error"

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My 2012 Audi a7 is giving me a "coolant temperature too high! Let engine run with vehicle stationary". I pulled over and let it idle for an extended amount of time and the engine temperature gauge only dropped one bar from

As a very first check make sure the coolant level is correct / up to the mark on the tank, then I'd first check that the radiator cooling fan is coming on as it should and if thats OK then replace the thermostat in the engine.

Whilst the thermostat is being replaced you might as well also reverse flush the cooling circuit (remove top hose to rad and use a hosepipe to push water into the engine until you get clear water out of the radiator hose) and top up with 30-50% fresh antifreeze. Also check that the small diameter bleed hoses that run from the top of the radiator and the top of the engine aren't blocked as this allow the air to vent back to the header tank automatically.

If you still have a problem then check that the water pump impeller / turbine isn't spinning on its shaft. You should be able to achieve this by removing the bottom hose from the engine and use a screwdriver or similar to feel for the water pump impeller blades, whilst your assistant turns the engine over by hand.
If you can stop the impeller with slight pressure from the screwdriver the pump needs replacing.

Also its possible the belt is slipping so its worth replacing its especially if the rubber ribs are cracked or it looks shiny on flat side of the belt - while its off check that the tensioner and other pulleys all spin freely the exception to this is the AC pump ( if fitted)

I'd also suggest ensuring that you've got all the air out of the system as this sort of episode can leave pockets of air trapped and prevent the coolant from circulating properly.

So check that the small hoses that run from the top of the engine and radiator that run back to the header / expansion tank are free flowing and not blocked

If these are OK then remove the tank pressure cap and run the engine from cold with the heater set to full hot

As the engine starts to warm, squeeze the large hoses running to the radiator to help displace any air - all the time keeping an eye on the level in the header tank, making sure it doesn't drop below the minimum

Once the engine is up to temperature the tank should be quite full. Switch the engine off and leave it to cool

Then top up to the mark once its all cold and replace the cap
Customer: replied 3 years ago.
In doing all th above I have to use a certain coolant correct? If so is this purple coolant available at any part store or is it strictly a dealer item? Additionally, if the coolant is low does this point to an issue with the cooling system such as a leak? According to the owners manual th system is sealed and should never require adding coolant.
Audi's do use a specific coolant which you shouldn't mix with other types as it can react inside the engine

however most garages and auto shops will stock it as its not a dealer only part

and yes if the coolnat is low then is quite possibly got a leak somewhere

If you have a tiny pinhole leak in a radiator then these often don't leak water but will lose water as steam ( steam molecules being small enough to pass through the hole where liquid cannot) take a look on the rad for any signs of localised corrosion and for areas that look like they've been 'steam cleaned'.

If all of this is OK it may be worth replacing the header tank cap as again you can lose coolant as steam if this is blowing off too early ( the cap should hold pressure of around 1Bar)

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