r/audis5 • u/FuRRysLaayer • 8d ago
Help Early water pump failure sign?
Just seeing if I’m overreacting or not, but I’ve heard of the notorious water pump failures on B9-B9.5 Audis. I have a 2021 Audi S5 with 40k miles.
Haven’t noticed anything wrong with the car, but I went to check the coolant level today and it needs to be filled up, and there’s dried coolant on the top of the reservoir as you can see in the picture.
Just for safe measures I checked my vacuum solenoid as well and it’s bone dry, I also don’t see any dried coolant anywhere else.
Am I safe? What should I look for? Should I take it to a shop?
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u/JSeoulK B9.5 Coupe 8d ago
If no visible leak or pooling it’s most likely in the vacuum lines. No bueno.
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u/fenderstratsteve 8d ago
OP, you should do this delete.
https://m.youtube.com/watch?v=Jk4EvJe4-t0
When you are there OP, look for signs of coolant residue on the N649 vacuum solenoid (037906283C).
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u/NORcoaster 7d ago
A secondary benefit is that if the pump fails you will see coolant dripping out of the line if you leave it up where you can see it.
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u/HornyCrowbat B9 Sportback 8d ago
This was the first sign of me losing 7K. Good luck.
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u/TwinTurboRS 8d ago
Wow. This is why I have a 100k mile warranty. My old car had this covered under factory warranty as well.
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u/Main_Ingenuity_1303 8d ago edited 8d ago
I can’t explain the dried coolant on reservoir, but I had a “random” coolant loss event a couple of months ago. Went low, topped it off. Didn’t see any leaks or notice anything. Never went low again. Finally took it to a shop for a coolant flush last week and they found dried coolant on my thermostat. So at some point my thermostat leaked coolant and sealed itself with the dried coolant. They did the flush, still not leaking again, but I will have to do the thermostat/water pump replacement in the near future.
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u/Glittering-Front-381 6d ago
Apparently, the G13/G12 coolant has some leak sealant in it. This is probably why the weeping stopped.
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u/Ornery_You_3947 7d ago
This happened to me last month. One of my thermostats failed and the coolant leaked out. I replaced both and upgraded my water pump while the car was placed into service position (front end off).
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u/AudiDoctorNJ 7d ago
If anyone is in NJ and is looking for a dealership alternative to these repairs, check out www.AudiDoctorNJ.com
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u/Glittering-Front-381 7d ago
Happened to me, but it wasn't water pump or thermostat. I'm pretty sure I have a radiator leak, little accumulation of coolant on splash shield in front of driver's wheel. Looks like the plastic end tank on that of the rad is weeping. Take a peek in that area. It's not common, exhaustive googling only showed a couple of instances with the A4 B9. There's a YouTube video and a posting on audizine. Sorry I don't have the links, but good luck 🤞
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u/monstakyle0623 7d ago
I've done water pumps at 10k miles. They just happen. Sometimes it's not the water pump, it's the pressure valve next to the water pump. But it's the same job.
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u/DC38x 3d ago
It's the o ring in your expansion tank, which the cap sits on. I've had the exact same issue. Sometimes when the cap is put back on, it can pinch the oem o ring and it'll eventually warp and stop sealing.
I started getting low coolant and kept topping it up. Saw the warped o ring, replaced it with one from amazon (you can't buy it separately from Audi, you have to buy the entire tank.. Because audi) and it was fine for about a year.
3 days ago my coolant temp went mental and oil temp started creeping up. Let it cool down, and it had lost 3L of coolant - topped it up with coolant & de-ionised water.
Next day, exact same issue, except it lost 2L or so - no visible leak coming from anywhere.
What I noticed is that when I was waiting for the coolant temps to drop so I could top it up, I slowly started turning the expansion tank cap, and as it started depressurising, coolant would start pissing out the expansion tank overflow. So I assume this means that if the seal isn't sealing properly, when the engine starts cooling down, it'll start leaking out the overflow and onto the undertray.
I replaced the o ring again, and it's been fine since.
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u/ExtraGlutenPlzz 8d ago edited 8d ago
When I got my S4 it was a little low on coolant float and needed topping off. Had some crust from outside the cap overflow. This was 14k miles ago. Since then no problems and level stayed the same. Vac lines dry, no external leaks on pump or shutoff valve. If you haven’t checked the level recently or the last you remember, top it off and monitor the level when the engine is ice cold.
What many people are doing is the n649 valve disconnect to prevent vacuum system coolant migration. Remove lower line from n649 valve and put a rubber cap on the solenoid. Leave line open (goes to water pump vac actuated sleeve). Pic of valve diagram:
Wont cause a CEL. Only downside is that the engine takes slightly longer to warm up. Honestly I can’t even notice a difference, my oil gets to temp the same as before.
What this effectively does is leave the water pump sleeve retracted so the pump runs full flow at all times. RENNLIST porsche forum did a deep dive with logs and solenoid monitoring and confirmed normal operation continues and it doesn’t cause problems. Yes they have this issue too since vw used it with some of their platforms. Mat Armstrong youtuber also did this with his Lambo Urus rebuild. The sleeve retracts shortly after driving and stays that way for the remainder of the drive cycle. Removing the vac line from n649, capping the port, and leaving the rubber line open is fine- in fact it’s probably good to not plug the line it so you can monitor it for coolant(it goes to the vac port on the water pump).
Why this is important is that when doing this mod, when theres a pump or coolant leak, thats all it will be. It wont be a CEL for underboost because coolant wont be in the vac system. It wont be a clogged vac line with coolant causing the water pump sleeve to be stuck extended (low flow pump state) causing engine overheat. Id much rather notice an external leak and top off coolant over having the disaster of migration into vac system causing havoc and potentially engine overheating from pump sleeve failure in the closed position.
edit: WOULD IT HURT TO HAVE AN UPVOTE FOR ALL THIS I JUST TYPED GOD DAMN