I too recently received the temperature warning on the dash. Pulled over and the radiator fan was spinning at full speed all while oil and cool temperatures were reading normal.
Popped the hood and everything was cool to the touch, no observable coolant leaks or smells. Hopped back in the car and drove home. Next day I start up, same thing happened. Same message, same fan at 100%, engine cool, no leaks or smell of coolant.
Broke out vcds and scanned. Only errors found were for the terrible front speakers. Posted on 034 FB group as I’m running stage 1 E85 on my 2018 S5 sportback. Everyone seems to point to a water pump problem.
In everything if read online, everyone has the water pump and thermostat replaced, but only to still have the same issue a day later. Because of that I replaced this same part. Bought the part for $50 on Amazon. It’s actually manufactured by pierberg, but doesn’t have Audi rings.
Long story short, replaced this in about 30 minutes, and the car has been running flawless for the last 500 miles. I was ready to drop off at Audi, but I felt like replacing this cheap part first was the better route since it’s what appears to fix the real issue. The real issue is a failed sensor, now a bad water pump! So many owners have been screwed out of thousands of dollars because of this shitty diagnosis.
Originally Posted by
Broke18SQ5
A valve can fail on top of the passenger cylinder head (N649) with a message on the dash coolant temperature to high. The valve is the coolant pump switching valve, The vehicle will overheat if driven. You can test this by removing the vacuum line on the front of the valve and plugging the vacuum line. If the message is gone and the engine is no longer over heating, the valve is faulty.
The valve is the correct solution however the part isn't listed correctly under any part distributor and is nearly impossible to find.
The part number for the valve on the vehicle is 037906283. Which is listed as a secondary air injection valve on FCPEuro for $27. And you can also buy it from oriellys auto under interchange part number 667-108 for 149.99 I can confirm both parts are the same number, identical, and work.
Part 037906283 has been used in tons of audi/vw vehicles over the years but still says it won't work when you put in anything 2018+ for a vehicle search... this is incorrect and it is the same part for the 3.0 Turbo sq5/s4 (not supercharged)
Part is easily changed on top of the passenger cylinder head. Slightly in front of the waste gate solenoid under a wire loom.
Originally Posted by
grimspd
Howdy:)
Just finished repairs on 2018 Audi S4 premium plus 3.0T. The coolant control valve described above was sticking in the open position. Verified with vacuum gauge in line between vacuum valve and coolant pump. Monitored power and ground to valve, and after the ecm switched the valve off (coolant temp. approx. 194 degrees as seen on scantool ) the vacuum did not release as expected. The vacuum valve was indeed stuck open. Upon inspection I could see some oily ooze under the valve (saw someone post a pic of this in another thread). Yes, the correct repair includes the valve, but that ooze came from somewhere (the coolant pump most likely). Also noted that when the vehicle was overheating due to the valve stuck open, the ecm stored a rationality code p1c1b - water pump mechanical malfunction. When this code sets, the message to check the coolant level appears in the MFI, even if the reservoir is full. Once the problem is fixed, and the fault is cleared, the message will be gone. Make sure no faults are stored before assuming your tank / level sensor is faulty. I replaced the coolant pump, control valve, and thermostat (since i was in there)... also the seals for the coolant pipes were not available separately -- replaced both pipes. I couldn't find any useful information on alldata or identifix, and these thread were helpful in thinking through the repairs. So THANK YOU!!! and i hope these other nuggets are helpful to the next person
oh yeah, you dont have to perform service position to do these repairs. the trickiest part was removing the air intake tubes. I used a Skewdriver (or also called offset screwdriver, Angle drive from Window Removal Set -VAS861001A- or Offset Screwdriver -T40398-) plus two bit driver extensions to get down there. The tube to the turbo inlet lower bolt was made easier with a ball end t30 bit.
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Some more info on overheating
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