Hello and a quick question
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Hello and a quick question
Hi everyone. It's a pleasure to come back to AudiWorld after a long long while. Life goes through motions but I'm glad to be able to enjoy this wonderful forum again, pick up gems, and contribute when I can. :-)
I posted the following on the A7/S7 forum but it seems quiet over there. Given these cars are technically close, I'm posting here too and hope someone can help.
I had my C7 S7 serviced yesterday and to bring her maintenance up to date, I got Audi to service the S-Tronic and the sports diff, plus replace brake fluid, spark plugs and the V-belt. At the end they told me all went well but they found signs of a minor leak/sippage at the coolant reservoire where the fluid level sensor plug is.
My question here is whether anyone here is familiar with this issue and if so, how serious is it? I'm going to keep an eye on it but was wondering if it's going to be a reliability concern and whether I need a new reservoire very soon. Any help is appreciated. Cheers!
I posted the following on the A7/S7 forum but it seems quiet over there. Given these cars are technically close, I'm posting here too and hope someone can help.
I had my C7 S7 serviced yesterday and to bring her maintenance up to date, I got Audi to service the S-Tronic and the sports diff, plus replace brake fluid, spark plugs and the V-belt. At the end they told me all went well but they found signs of a minor leak/sippage at the coolant reservoire where the fluid level sensor plug is.
My question here is whether anyone here is familiar with this issue and if so, how serious is it? I'm going to keep an eye on it but was wondering if it's going to be a reliability concern and whether I need a new reservoire very soon. Any help is appreciated. Cheers!
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From: BC, Canada
No V belts on these cars, just a flat style serpentine belt. (x2)
A common area for a leak around the reservoir is the actual coolant cap, the ORing gets old and flat, causing coolant to run down the side. You can either just replace the ORing or get a whole new cap.
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Thank you Sallad. V-belt is the wording they used in their initial report, quote and invoice. Without getting into the semantics, I guess we're both referring to the same actual belt. :-)
They also provided a photo of the actual point where they said they found the leak. You raise a good point though. If a leak finds its way down there, it'll be hard to tell. I noticed there's too much coolant in the reservoire. This can contribute to the situation if your theory is the case. I'll take some coolant off the top to bring it to the correct level and then keep an eye on it. Thanks for the hint!
They also provided a photo of the actual point where they said they found the leak. You raise a good point though. If a leak finds its way down there, it'll be hard to tell. I noticed there's too much coolant in the reservoire. This can contribute to the situation if your theory is the case. I'll take some coolant off the top to bring it to the correct level and then keep an eye on it. Thanks for the hint!
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Keep an eye on the coolant level and change when you can fit the time in. Might be the res, might be the o-ring on the sensor, could be just a matter of pulling the sensor and put a dab of something to help seal the o-ring. Understand that at idle with the engine cool you will not see much of anything for a leak but at temp and under pressure is when you will see it leak.
FCP has a replacement res for $45 made by Meyle. You can spend $100 for the OEM res as well with them but I would guess at a 99.9% certainty that the OEM is Meyle with a $50 4 ring surcharge. Another $20 or so for a jug of antifreeze. Job should take less than 30 minutes but a shop will charge you an hour of labor so $175 - $250 or more.
If you decide to have this repaired at a shop there is no reason to take it back to Audi, any shop can do this. You don't even need an Audi specialty shop. Factor G-12 or 13 coolant would be best but Zerex Euro will work perfectly fine.
FCP has a replacement res for $45 made by Meyle. You can spend $100 for the OEM res as well with them but I would guess at a 99.9% certainty that the OEM is Meyle with a $50 4 ring surcharge. Another $20 or so for a jug of antifreeze. Job should take less than 30 minutes but a shop will charge you an hour of labor so $175 - $250 or more.
If you decide to have this repaired at a shop there is no reason to take it back to Audi, any shop can do this. You don't even need an Audi specialty shop. Factor G-12 or 13 coolant would be best but Zerex Euro will work perfectly fine.
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Thank you - much appreciate the information and suggestions. :-)
I had noticed technicians must have overfilled the coolant tank when I arrived home on the day I picked the car up. There were some smudges of dried coolant on the tank which I wiped. Beneath the sensor felt dry. Even after the engine was cool the day after, the tank was full to the hilt.
After reading the comments here, I siphoned out 600 ml and brought the level to the range and marked it. I have now driven the car a few times. The coolant level seems stable and no signs of leak around the tank or under the sensor housing. Not sure when the mechanic noticed the sign of leakage in the first place. If it was after they filled the tank, it could simply be that the tank was too full and when hot, some leaked from the cap o-ring.
I'll continue and keep an eye on it. Hopefully it's been a misdiagnosis.
Thanks again.
I had noticed technicians must have overfilled the coolant tank when I arrived home on the day I picked the car up. There were some smudges of dried coolant on the tank which I wiped. Beneath the sensor felt dry. Even after the engine was cool the day after, the tank was full to the hilt.
After reading the comments here, I siphoned out 600 ml and brought the level to the range and marked it. I have now driven the car a few times. The coolant level seems stable and no signs of leak around the tank or under the sensor housing. Not sure when the mechanic noticed the sign of leakage in the first place. If it was after they filled the tank, it could simply be that the tank was too full and when hot, some leaked from the cap o-ring.
I'll continue and keep an eye on it. Hopefully it's been a misdiagnosis.
Thanks again.
Last edited by dA4banger.au; Nov 22, 2025 at 01:38 PM.
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