themoveforward

Hi Guys,

I apologize in advance for the long missive, but I'm just trying to be as thorough as possible.

For starters, my car is running a Stage II GIAC tune, with an AWE cold air intake and exhaust system. 2014 B8.5 S4 w/ 16k miles.

On a recent trip from Long Island, NY to Montreal, Canada I decided to let my friend drive for a bit and relax. He decided to do a bit of "spirited" driving and after about an hour a message appeared on the dash that stated "Coolant System Failure".

Having already driven 200 miles I decided to continue driving the rest of the journey while monitoring the coolant temperature. I checked under the hood for leaks which there were none and the coolant reservoir is full, which a later diagnosis at a shop confirmed.

I managed to continue the drive there and back to Long Island which is about 400 miles total. About 5-6 times during that period the coolant temperature would begin to rise when there was additional stress placed on the engine such as going up a steep grade, however not above the 3/4 mark on the temp gauge. Turning the heat to high and letting it blow would drop the temp back to normal.

About an hour after the warning message appeared I stopped at an auto parts shop to borrow a code reader and clear the code. That worked, however after about 15 minutes on the highway the message appeared again without the coolant temp rising (though it would sporadically rise afterwards like I mentioned).

For the last 300+ miles of driving the temp has not strayed from the normal halfway mark on the temp gauge.

When I returned home, I brought the car to a mechanic who did some testing and confirmed there are no leaks with the system, that the coolant temp is around 160-170F (70-75C) and engine temp is around 200-210F (95-100C). They also stated that the coolant smelled acidic and looked dark possibly indicating electrolysis. They pointed to possible water pump failure but couldn't prove it without removing the pump.

I figured if the water pump is failing it would lead to consistently high coolant temperatures though.

At that point however the lead mechanic said he wasn't comfortable working on a newer Audi like this in which he didn't have experience and suggested I take it directly to Audi (whom I can't bring it to since they'll TD1 it immediately).

They cleared the code and sent me on my way. I've been driving the car for the last week without an issue and without the message appearing again.

Yesterday I dropped the car off to an Audi specialist who said based on the previous diagnosis and the freeze frame I pulled via VAGCOM, that it's the water pump and needs to be replaced at a cost of $932USD including labor.

I contacted the shop who did the tune (AWE) as well and they're not sure on the diagnosis based on the info presented as well. He basically stated to keep driving the car if the coolant temps still aren't an issue and its not throwing codes again.

I don't drive the car very far on most occasions usually 6-10 when I do and that's only a few days a week (hence 16k miles in 3 years). I'm thinking that this problem has been around for a while/months and just hasn't made itself known since I don't stress the engine for long periods of time and this most recent trip is the longest and furthest it's been on.

I'm not sure whose advice to take at this point and I'm looking for an outside opinion from you guys.

Thanks in advance.
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DrGP

While the Supercharger is off, it would be prudent to replace the T stat as well. Or you may be pulling the SC off again to replace it when it goes bad. I said when, not if. But in the past, when the plastic WPs failed, it was catastrophic and let you stranded with no fluid in the coolant reservoir. Same thing happens if the IC radiator gets punctured by road debris. Both of these problems happened to me .When the T stat fails, it usually fails closed causing an overheating problem. I'm wondering if the T stat could be starting to fail and sticking closed and then finally opening?

AForePlayin'03

Possible to flash the ECU back to stock to potentially avoid the TD1 and have the dealer look at it under warranty? I don't think they'd flag you for an exhaust and CAI.

themoveforward

I was thinking it could possibly be the thermostat, but the detailed diag I just got the other day said they didn't measure a significant increase in temp at the thermostat but there was a significant differential at the water pump itself.

Still wouldn't explain why it's functioning well enough to give it WOT for a bit and the coolant temp doesn't budge.

Either way I plan on having the thermostat replaced right along with the water pump if I have it done.

themoveforward

I guess it would be possible to flash back to stock, but I'm pretty sure they can tell from the flash counter that the ECU has been messed with anyway.

Plus I have the shortened supercharger pulley on there that they would see right away.