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Discussion Starter · #1 · (Edited)
Hello guys,
Audi S3 2015 CJX, 90k kilometers mileage.
I'm running out of ideas.
It started with water pump leak - replaced.
While bleeding coolant system after replacing water pump thermostat housing we noticed there is problem with bleeding and water is "bubbling" (video).
My mechanic said it's normal behaviour, because of pressures etc. I didn't quite believe in that, because there isn't any "boiling" in my father's A3 2.0 tfsi and even my friend's same S3.
I was trying to make test for CO2 in coolant, but it was impossible due coolant reaching too fast to the tester.
Engine was sometimes running a bit I did basic diagnosis in VCDS - it showed misfires on all 4 cylinders. Few misfires after 10 min on idle and about 10-20 misfires on each cylinder after hard 1 km ride. Also there was something which looked like coolant under oil cap (picture) - mechanic said it's not coolant (then WTF is this)
Head was reassembled - no signs of wear or anything on gasket and cylinders. Head was checked under pressure with hot water for cracks, then planned and assembled. Coolant system was checked under air pressure. Head and block are straight. Compression is fine
Result after head regeneration - same problem with boling coolant, no misfires on idle, no coolant in oil.
At least that's what mechanic said. There wasn't test drive yet, because car was on summer tyres. I am picking it up tommorow and will check by myself on road if there really aren't misfires and no coolant in oil.

Car has no problem with power, no white cloud from exhaust. Oil coolant radiator wasn't checked yet, because he said that if it was damaged then oil would be in coolant, because of much higher pressure of oil. Bottom of the engine block wasn't checked too.

I'd appreciate any ideas why is this happening & what else could be checked.
Video

 

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I know we have a couple secondary coolant pumps. Not sure if maybe one has failed and causing a lack of coolant flow and overheating. I'd scan the car for an error code?

It is common for air to need to work its way through the system when refilling with coolant for the first time.

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Discussion Starter · #3 ·
Car is probably after chiptuning. I've discovered turbo is pumping almost 1.6 bar (23 psi) in peak. I'm going to restore ECU to stock tommorow. Also EPC error with turned off 4th cylinder (too high pressure) showed up. Probably due too many misfires or knocking. I Also error about blocked auxiliary water pump showed up yesterday, but it may be related with me changing HVAC hot country settings from cold country to normal.
 

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Discussion Starter · #4 ·
After installing new stock ecu&tcu software misfires are gone. Engine is still lil bit shaking for every several seconds though. I don't know what to check about this shaking if there aren't any misfires.. We've discovered that ignition timing angle is up to -5* on every cylinder from 5 to 6k rpm. Is it normal for these engines?
 
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