Coolant leak

[RickV]

I just noticed a slow coolant leak under the oil dipstick. I forgot the name of this plastic fitting that it's leaking from. It's actually dripping from where the metal pipe goes into it. Can someone help with a fix please?

[80sGuy]

Sounds like your thermostat as they are connected to.

[RickV]

Good call, I believe that's the problem. Thanks

[Theiceman]

leaking thermostat, may want to consider the rear flange at the same time as you will be doing a flush and fill. rear flange is a PITA though.

[RickV]

leaking thermostat, may want to consider the rear flange at the same time as you will be doing a flush and fill. rear flange is a PITA though.

Hey pal how you doing? You helped me out alot on the engine rebuild and swap I did on this car back in March of 2023. I had that weird issue with the phaser. When I put the newly refurbished engine in and went to start it it went out of time and bent all the intake valves. You discovered that the phaser was bad and was already advanced on the engine I rebuilt which causes the pin to break and throw the intake cam out of time. I can laugh about that now ... Haha 🙄 not really. Lol
I had replaced the rear flange and the thermostat and pretty much everything else on this engine before I installed it. It's been solid since then. No issues until this drip. That's why I'm surprised it's even there. I've only put about 8k miles on it since.

[Theiceman]

Hey pal how you doing? You helped me out alot on the engine rebuild and swap I did on this car back in March of 2023. I had that weird issue with the phaser. When I put the newly refurbished engine in and went to start it it went out of time and bent all the intake valves. You discovered that the phaser was bad and was already advanced on the engine I rebuilt which causes the pin to break and throw the intake cam out of time. I can laugh about that now ... Haha 🙄 not really. Lol
I had replaced the rear flange and the thermostat and pretty much everything else on this engine before I installed it. It's been solid since then. No issues until this drip. That's why I'm surprised it's even there. I've only put about 8k miles on it since.

I can tell you a long time ago when i firs did my stat i noticed it leaking shortly after ... I realized i had put a couple of things on in the wrong order. I cant remember the details as it was so long ago , but there is a definite order to put the things on under one of the bolts. May be worth having a look at. Wish i could remember what the specific issue was.

[CycloSteve]

It could just be the o-ring on the metal pipe which is going into the t-stat in the picture.

If you replaced the t-stat, was it a VAG one? Aftermarket ones seem to have more issues, failing much faster.

[RickV]

I can tell you a long time ago when i firs did my stat i noticed it leaking shortly after ... I realized i had put a couple of things on in the wrong order. I cant remember the details as it was so long ago , but there is a definite order to put the things on under one of the bolts. May be worth having a look at. Wish i could remember what the specific issue was.

Ok good to know. All the parts I replaced (including the thermostat) were installed while the engine was hanging in my garage so I had really good accessibility and watched a crap ton of YouTube videos. However, I guess it is possible I may have missed a specific detail. For now I put a bottle of K-seal in with the coolant to see if it seals the leak. If it doesn't I guess I'll be buying a new thermostat and play mechanic again.

[80sGuy]

Your thermostat shouldn't failed this soon...UNLESS... you're using mickey-mouse parts. But before this have you checked anything else, like maybe the o-ring on the hard line connected to the unit? When I replaced my thermostat I also replaced that particular o-ring just in case. But again, (some) non-genuine parts can also screw things up. So carefully and thoroughly check it through. I'd go with the genuine parts if you haven't as mine has been holding up great since it was first replaced back in Feb 2023!

New O-Ring (right)
https://live.staticflickr.com/65535/54187568617_12dc780c88_c.jpg

Goes in hard line (seen underneath the rubber hose) insert to thermostat
https://live.staticflickr.com/65535/54188456296_9e2c3237a7_c.jpg

[RickV]

Your thermostat shouldn't failed this soon...UNLESS... you're using mickey-mouse parts. But before this have you checked anything else, like maybe the o-ring on the hard line connected to the unit? When I replaced my thermostat I also replaced that particular o-ring just in case. But again, (some) non-genuine parts can also screw things up. So carefully and thoroughly check it through. I'd go with the genuine parts if you haven't as mine has been holding up great since it was first replaced back in Feb 2023!

New O-Ring (right)
https://live.staticflickr.com/65535/54187568617_12dc780c88_c.jpg

Goes in hard line (seen underneath the rubber hose) insert to thermostat
https://live.staticflickr.com/65535/54188456296_9e2c3237a7_c.jpg

The drip does appear to be coming from the hard line. I was trying to remember what that connection looked like because what you're saying was my thought as well. Thanks for showing that. I only used OEM quality parts or better for every part I replaced which is why I was surprised by this. I honestly can't remember if I replaced that o-ring. If it looked good it's possible I may have left it and just lubed it. The K-seal I added did stop the leak for now but I'll definitely look into that o-ring the next chance I get. Thanks pal.

[Theiceman]

i made these comments after i did my thermostat as it started leaking after.....

Mine leaked right after this and it was due to my own fault . posting this comments so others don't do the same mistake. I kept seeing coolant above the drivers engine mount. took it all apart and discovered my error . the hard pipe that has the oring in it goes in first against the thermostat. then the other small verticle pipe , then the torx screw into the thermostat. I made the mistake of putting the other pipe first then the coolant pipe. the oring in the coolant pipe does not seat properly if you do them in the wrong order. as the bracket for the coolant pipe is further away from the stat causing it to not seat the oring properly. Not a big deal and cost me a couple of hours and more coolant .. all good now.

[RickV]

i made these comments after i did my thermostat as it started leaking after.....

Mine leaked right after this and it was due to my own fault . posting this comments so others don't do the same mistake. I kept seeing coolant above the drivers engine mount. took it all apart and discovered my error . the hard pipe that has the oring in it goes in first against the thermostat. then the other small verticle pipe , then the torx screw into the thermostat. I made the mistake of putting the other pipe first then the coolant pipe. the oring in the coolant pipe does not seat properly if you do them in the wrong order. as the bracket for the coolant pipe is further away from the stat causing it to not seat the oring properly. Not a big deal and cost me a couple of hours and more coolant .. all good now.

Ok good to know. I honestly don't remember how I installed mine since it was almost 2 years ago but I'll definitely keep note of that if I have to take it apart. That K-seal stopped the leak, at least for now so I'll wait it out and see what happens. I appreciate the help like always.

[Phil Audi B7]

If it’s leaking by the oil dipstick it’s most likely that O ring that attaches to the hard pipe. The thermostat is located in the back of the engine, passenger side. This doesn’t seem like the problem. I agree with Ice on this one. Hardpipe O ring

[80sGuy]

.....

......The thermostat is located in the back of the engine, passenger side.....
You mean the 'Coolant Flange'?

[Phil Audi B7]

The coolant flange also houses the thermostat, passenger side rear of the engine.
The leak you mentioned is by the dipstick, it’s most likely that small O ring from the hard pipe that’s the issue. Kind of a pain to loosen up the hard pipe but it’s an easy and cheap fix

[Phil Audi B7]

I need to correct myself here, there’s a thermostat sensor on the passenger side rear that’s part of the coolant flange. This area isn’t your issue.
There is another flange by the alternator that connects to a hard pipe that’s houses your thermostat.