What am I doing wrong?

[79TA7.6]

I keep getting a leak at my thermostat housing. I am torquing the bolts to the correct sped, I clean the area as best I can. The last time I even took a little emery cloth in case there were some rough spots I was not seeing. I replace the housing and o-ring about twice a year. This is getting annoying and expensive.

 

[BobnOH]

Are you using a new flange, maybe a new o-ring?
http://forums.tdiclub.com/showthread.php?t=264619

 

[79TA7.6]

Yes. Everything but the thermostat itself is brand new when I fix the leak. I will read your linked how to and see if maybe I am missing something.

 

[JB05]

What brand is the t-stat?

 

[Bran Diezel]

Did you get the right o-ring? I did that once on a car and realized they sold me the wrong one. The right one is about 2x as thick as a normal o-ring.

 

[oilhammer]

This is why we only use OE stuff from Volkswagen. Thermostat, o-ring, and flange, every time, never an issue. A lot of the non-OE stuff (Meyle, Uro, etc.) are all Chinacrap.

 

[79TA7.6]

I only get stuff from IDParts or BoraParts. I never get stuff elsewhere. Not worth the headache. That being said, the last thermostat and housing/o-ring came from boraparts.

Housing: http://shopping.boraparts.com/product_info.php?products_id=347
Thermostat: http://shopping.boraparts.com/product_info.php?products_id=346

If there are issues with these please let me know and Iwill order from somewhere else next time. I have yet to order the replacement parts for this leak.

 

[79TA7.6]

I have been thinking of having my machine shop make me a metal plate to help apply equal pressure all the way over the housing. This plate would have cutouts for all of the factory molded gussets that are currently on the housing. Does anyone see an issue in doing this? I know this is more of a bandaid fix than anything, but I am willing to try about anything right now.

 

[oilhammer]

I don't know whose part that is, I just know I too have had short-lived plastic water flanges on Volkswagens (as well as other non-VAG products) that were non-OE. The genuine Volkswagen water neck will have a VAG part number on it, with the VW and Audi logos, as does the thermostat. O-ring you really couldn't tell.

And to install these, you put the o-ring on the flange, then twist-lock the thermostat in place, and install it to the block as an assembly.

I keep TDI (as well as VAG gassers) thermostats all made up in little baggies, ready to go.

 

[79TA7.6]

I might see if I can get my next housing from the dealer. I hate to do that, but I honestly do not remember if I saw the VW Audi symbol or not. I have not had an issue with boraparts in the past, except for this housing. And it may not even be the housing. I might just be doing something wrong and just have not figured it out yet.

 

[CopaMundial]

Are you sure the leak is coming from the housing itself?

There are two O-rings in that area that can leak.
One is on the T-stat housing to block. The other is a small o-ring that seals the end of the hard coolant pipe to the flange.

Here is a video showing a little about both.
http://www.youtube.com/watch?v=eEak8EM4KDM

 

[oilhammer]

Good point, that o-ring on the pipe can leak too.

 

[79TA7.6]

The first time it leaked on me that is where I thought it was coming from. I am able to see around the metal pipe and that is not where it is leaking from. I do see water directly below the housing, but mainly on the right side. So far every time I have changed the housing and place a new o-ring, it stops leaking for several months.

I will get a new housing, likely from the dealer this time just to be sure it is a genuine VW part, and see how this next time goes.

BTW, I do have that gasket somewhere. The first time it was leaking I was not sure where it was coming from so I bought this gasket and the housing and o-ring.

 

[CopaMundial]

Ok, last idea, the bolts that connect the housing to the block are supposed to be one-time use. Have you been re-using the same bolts?

If you want to avoid messing w/ dealership for parts, IDParts has the OEM stuff clearly marked as such in their menu. Just put your model and year in the filter on top, then search for 'Thermostat'. You will see both OEM and other options listed.

http://www.idparts.com/catalog/product_info.php?products_id=3402

 

[MidnightBlue]

... the last thermostat and housing/o-ring came from boraparts.

Housing: http://shopping.boraparts.com/product_info.php?products_id=347
Thermostat: http://shopping.boraparts.com/product_info.php?products_id=346

Those look like the exact parts I got from Bora Parts last fall. I had zero problems with them. No leak at the flange since I installed it, and a recent VCDS log showed temperature steady at just over 90C.

And I reused the bolts (hadn't found the replacements on Bora Parts when I ordered). At 11 ft/lbs. torque, I don't understand why they are supposed to be one-time use. But it doesn't cost much to try some new ones! Maybe a previous owner over-torqued them?

Any chance the holes for the flange bolts are goobered up somehow, so you reach the right torque before they're actually tightened down all the way? I don't remember (and I'm too lazy to go out and look tonight), are they blind holes that could have some dirt in the bottom?

 

[79TA7.6]

I like the idea of checking to be sure the threads are clean. When I replace the housing and o-ring I will run a tap in them to make sure there is nothing stopping them.

 

[whitedog]

My Bentley shows 18 Lb/ft and no notes on them being one time use.

 

[kyle_h]

At least it's not a tsi thermostat all I gotta say!


Sent from my iPhone using the Tapatalk app, so that explains the typos...

 

[CopaMundial]

My Bentley shows 18 Lb/ft and no notes on them being one time use.

I think it's 15 Nm in the Bentley (~11 ft/lb as MidnightBlue converted no doubt).
The one-time-use mention that I was referring to came from the summary on IDParts page. I also don't see anything about it in Bentley, and no 'X torque + Y degrees' shenanigans. So yeah, the one time use thing is probably a stretch (no pun intended)... but if I had been replacing my thermostat housing twice a year then I would probably be willing to toss some fasteners on the pile to avoid another repeat. Checking for obstructions in the threads as was mentioned is an excellent idea too.

 

[whitedog]

Our books must be different because I just looked again and it shows 25 Nm (18 ft-lb).

And remember that sometimes they call for one time use because a bolt may have a thread locking patch on it. It's not always a TTY bolt.

Edit:

That was from the Bentley for the Beetle up to 2002, My Bentley for the Jetta - ALH and BEW - up to 2005 shows 15 Nm (11 ft-lb).

So we were both reading right, but one of our books is wrong.

So basically, what we just found is that when someone says that everything that you need to know is in the Bentley, the Bentley isn't always right.

I just looked at a torque chart and the standard torque for an 8 MM grade 4.8 bolt is 15 Nm. Are those thermostat flange bolts grade 4.8? I don't know. I really don't.

If I were the OP, I would clean out the holes and get the parts from VW. One thing that I have found is that thermostats should be the same as what you would get from the dealer. "OEM Quality" just isn't good enough.