Cooling system help

[Rare Ara S3]

https://www.dropbox.com/sh/95szoktpexsruak/AAC1rXZY0qI-a5EewOxiDE-Sa?dl=0&preview=Engine_Manual.pdf

This has the official VW coolant bleeding procedure listed. It also goes into bleeding and flushing specific sections of the coolant systems

you may just be a life saver.

 

[AceHammer]

This step about removing the connector for the temp probe might help, never heard of doing this before

Edit - And hey at least it's nice to know that if your coolant sensor fails the car makes an effort to not overheat

 

[Rare Ara S3]

View attachment 207596
This step about removing the connector for the temp probe might help, never heard of doing this before

Edit - And hey at least it's nice to know that if your coolant sensor fails the car makes an effort to not overheat

i hadnt seen this yet. im still stuck on the fact that they use a scan tool while bleeding. I think a trip to the dealer is going to be required.

 

[Rare Ara S3]

Well I tried running it with the coolant sensor unplugged and it didnt help. The fans run at least. I feel a little heat coming off the radiator after it runs a while but when I drive the coolant temp goes up and doesnt cool down like it should. Seems odd that a waterpump that worked before it was removed would just take a dump. If its not an air pocket then I'm stumped. Or worst case a head gasket? The engine was just rebuilt! FML Im hopeful that the dealer can run through their process of bleeding it with their diagnostic tools.

 

[AceHammer]

If the water pump was removed sounds like something wasn't installed correctly or it got damaged. Head gasket you would be losing coolant and they seem to be very rare on this platform.

 

[gixxerfool]

If the water pump was removed sounds like something wasn't installed correctly or it got damaged. Head gasket you would be losing coolant and they seem to be very rare on this platform.

In the past I have head gaskets popped that don’t leak externally, but suck air in on cool down and belch all the coolant. Not on this platform, but I have had it.

BMWs you need to run a specific purge cycle with the scan tool to get the air out of the electric water pump. Could the air be binding in the auxiliary pump and not able to purge itself? Just a thought.

 

[AceHammer]

Never heard of anything with the aux pump before. The biggest coolant issue with these cars is the water pump and thermostat housing cracking and leaking coolant, it is possible that it cracked in a way that air is being sucked in.

IMO if I removed the water pump on one of these cars I would never put the old one back on, the housing is just too fragile.

 

[gixxerfool]

Never heard of anything with the aux pump before. The biggest coolant issue with these cars is the water pump and thermostat housing cracking and leaking coolant, it is possible that it cracked in a way that air is being sucked in.

IMO if I removed the water pump on one of these cars I would never put the old one back on, the housing is just too fragile.

Yeah. It was just a thought. I agree though. Going that far in, ain’t worth it.

 

[AceHammer]

Really wish someone would come out with an all-aluminum water pump like the mk6. Would buy that in a heartbeat

 

[Rare Ara S3]

I would typically agree on not installing old parts. This car had 28k miles on it and the pump is in excellent condition. I had considered buying one anyways but I looked it over and it doesn’t have any cracks. There was never any leaks nor any oil leaking onto it

 

[AceHammer]

When you drive does the radiator actually get hot? Mine after a short drive with a few pulls quickly gets to the point I don't want to touch it.

I'm trying to find it but when the coolant is cold it is not sent through the radiator to speed warmup. It sounds like your car could be stuck in this mode

I would ensure all electrical connections on the thermostat are fully seated, besides that, you could have a faulty t-stat.

Edit - Found it, this goes into detail about exactly how the t-stat works https://procarmanuals.com/vag-ssp-606-audi-1-8l-2-0l-tfsi-engine/
On page 35 you can see the different coolant modes the car goes into, sounds like it is stuck in one of them. I'll try to see if there is a test procedure for N493 the motor that changes the coolant valves

Edit 2 - Above 235F the t-stat has an 'emergency' wax capsule that melts which will completely bypass the valve system and allow water to flow to the radiators. So I guess this is a hard limit to these cars, as if that melts you will need to replace the thermostat

 

[Rare Ara S3]

When you drive does the radiator actually get hot? Mine after a short drive with a few pulls quickly gets to the point I don't want to touch it.

I'm trying to find it but when the coolant is cold it is not sent through the radiator to speed warmup. It sounds like your car could be stuck in this mode

I would ensure all electrical connections on the thermostat are fully seated, besides that, you could have a faulty t-stat.

Edit - Found it, this goes into detail about exactly how the t-stat works https://procarmanuals.com/vag-ssp-606-audi-1-8l-2-0l-tfsi-engine/
On page 35 you can see the different coolant modes the car goes into, sounds like it is stuck in one of them. I'll try to see if there is a test procedure for N493 the motor that changes the coolant valves

Edit 2 - Above 235F the t-stat has an 'emergency' wax capsule that melts which will completely bypass the valve system and allow water to flow to the radiators. So I guess this is a hard limit to these cars, as if that melts you will need to replace the thermostat

I think I’d be seeing an improvement if that melted lol. Everything is connected. I checked and rechecked. Not to mention Id get a fault if the tstat was unplugged. Having disassembled and reassembled half the car this is such a silly problem to have. I guess it could be worse. The water pump is not difficult to install or replace. Either way I flatbedded it to the dealership.

 

[Rare Ara S3]

226 is the target coolant temp at idle on a stock tune. I recently replaced my water pump. I just left the coolant res cap off, started the car, let it warm up. Every so often squeeze the larger hoses to work out the air bubbles. I don't know if this 'trick' even applies to these cars, but I also turned the heat on full hot. It was funny, I had 0 heat, and then randomly at some point the heat came in, like some valve on the water pump finally opened up.

Anyways, I've done it this way 2x times now and never had any bleeding issues. Pretty much how I do any car that doesn't have a radiator cap and seems to work fine. Elevating the front of the car (drive on ramps) might not hurt either to elevate it even more.

And to be honest I am not sure about the fans, to answer the original question.

where did you find the info on the temperature target at idle? Also what failed on your water pump?

 

[aaronc7]

where did you find the info on the temperature target at idle? Also what failed on your water pump?

Doing my own tuning with HP Tuners. I guess it's actually 225*, see below.

Mine was a really minor leak and would only go down from time to time vs consistently over time. It was kinda weird, but I already had the intake manifold off for MPI, so it was a no brainer to swap it. It appeared to be leaking on the 'front' where the 'water neck' looking thing is bolted down with the 4 torx screws.

 

[gixxerfool]

I am sure you have already tried this, but I will throw this out there. I have had cars over the years that are absolute bears to bleed. This has worked on cars with overflow bottles and surge tanks. I will over fill the bottle and close the system. Let it get as hot as you can then shut it off and let it cool. As the system cools it will purge the Air and replace it with the excess coolant.