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So coolant leaks when I pressure test with the engine cold, but not when it's warm.
It reaches under 1 bar and then it just starts dripping under the car.
Naturally because it's so crammed and tight I can't see where the leak is.
Don't think they would seal up completely when engine is warm?
When I just make many short runs around town I loose a lot of coolant, but if I take a longer drive, 2 hours or longer I loose very little.
Typically a water pump will not leak a large amount of coolant. When the shaft seal goes bad it will slowly leak coolant from the weep hole.
When you pressure test your cooling system when you car is warm, do you let it sit for 30mins to an hour to see if the pressure drops? When the car is warm it probably doesn’t seal completely, just reduces the amount of coolant lost. Or it could be burning off on a hot engine. When coolant dries it leaves a white residue, I’d suggest getting an inspection mirror and looking at the front of the engine for white residue. That will tell you where your leak is coming from.
Im not familiar with the 3,0 engine but the radiator hose end caps are common leak spot as well the coolant crossover pipe( if your engine had one)
So I noticed there was this area under the supercharger where the coolant first builds up and then runs down when it's full. The black arrow points to the place.
Was quite a lot of fluid there that I sucked out with a syringe. Pumped up the pressure again and the level started rising. Used a endoscope camera to get a better look.
Still have no idea where the actual leak is
Help from people with experience of the 3.0 tfsi engine?
Further digging around with the endoscope revealed another pool of coolant behind the water pump.
When I sucked this dry and put the pressure on this area started filling up again, but not the area in the back.
Metalhead,
It is highly probable you have a leak from the thermostat. I had similar leak in our 09 A6 last year that was caused by corroded area under thermostat gasket. As engine was overheating I had to replace thermostat and so that leak was also fixed. I had to make extra silicone gasket to flatten the seat for thermostat gasket. Hope I helped.
How many hrs should replacing thermostat be at a garage shop about?
Not shure about labor hours but pro job is rather pricey.
Here is the useful link: https://www.audiworld.com/how-tos/a/...rmostat-422162
There are multiple expertly presented diy over this thread and YouTube channels that will help you to understand the whole process.
I have done it twice last winter, took me two afternoons each time. Thermostats in early batches of 3.0t's are prone to failure so there is an opportunity to safely replace it, together with both belts.
I have ordered both water pump and thermostat as they were pretty cheap.
But what seals and o-rings (parts nmbr) needs replacing when SC is removed and re-installed?
01-19-2019, 05:03 AM
3.0 tfsi coolant leak when cold
