Metal Coolant Flange

[ZipMeUpJ]

Tis the season for "my heat is blowing cold air" threads. Have to park the bike in the garage for the season and tidy up the b6 for the cold months.

I've recently discovered a quick coolant leak the other day, while working on another issue of the "flooded ecu box" variety. Get on the floor to see where the fresh stream of Coolant on the pavment leads, and lo and behold, it's coming off the front of the tranny.

I hate changing this part, but I love this car too much that I just have to accept it as a necessary nuisance. I've also discovered that theres an actual metal variant of this part for purchase now.

What I am skeptical about is whether it being metal was the change in design it needed to not be such a weak part in the coolant system. Isn't it the o-ring that generally fails? I'm on the fence about purchasing that variant instead of the plastic one, if it is just the o-ring that keeps failing on me. It has been 3/4 changes for me, with 2 of that 3 being AUDI OEM branded parts.

I know it's a popular part that fails on these engines, but is it the oring, or the physical plastic part that fails for most people?

[B6_A4_Kid]

I've replaced two of these personally on two b6s. First one had an actual blow out in the plastic, second was just o ring failure.


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[egovreau]

I installed the aluminum coolant flange a few months ago...so far, so good. My plastic flange wasn't leaking yet, but failure was imminent. Not only was one of the ports cracked, but the o-ring groove started to disintegrate as I removed it.

Sent from the 7th Galaxy.

[jacobsen]

Tis the season for "my heat is blowing cold air" threads. Have to park the bike in the garage for the season and tidy up the b6 for the cold months.

I've recently discovered a quick coolant leak the other day, while working on another issue of the "flooded ecu box" variety. Get on the floor to see where the fresh stream of Coolant on the pavment leads, and lo and behold, it's coming off the front of the tranny.

I hate changing this part, but I love this car too much that I just have to accept it as a necessary nuisance. I've also discovered that theres an actual metal variant of this part for purchase now.

What I am skeptical about is whether it being metal was the change in design it needed to not be such a weak part in the coolant system. Isn't it the o-ring that generally fails? I'm on the fence about purchasing that variant instead of the plastic one, if it is just the o-ring that keeps failing on me? It has been 3/4 changes for me, with 2 of that 3 being. AUDI OEM branded parts.

I know it's a popular part that fails on these engines, but is it the o-ring or the physical plastic part that fails for most people?

I have about 150 thousand miles on my 1.8 and I've never replace the coolant flange or had a leak from the coolant flange. I did however have to replace my coolant flange Quick Connect coupler which goes to the heater core. It literally disintegrated. I think it is the seal that typically fails. I do believe however that, plastic does not do well over continuous heat Cycles. If I were you I would go for the upgraded aluminum part and also search out the highest quality seal you can find. I've never had to replace it so I don't have any direct info about it Kama I did reach my hand back and I figured I could replace it someday if I had to because I could feel both the studs holding it in, I install the new oil feed and one of the studs holds that in the back.

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[Spike00513]

There's also one for VW MKIV 1.8T, and I hear 2.7T'ers switch plastic thermostat housing to an OE metal version.

I don't think this answers your question though.

[jacobsen]

The main thing about seals is you don't want to squish them too much and you don't want them to loose. There's a Goldilocks zone.

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[ZipMeUpJ]

I think that is the issue. I can't find that goldilocks zone. Do you think its possible, with any benefit at all to fill the space that the o-ring would, with something else other than an oring to get a better seal? Maybe some high-temp gasket maker? Something has to be better than an o-ring.

[jacobsen]

I think that is the issue. I can't find that goldilocks zone. Do you think its possible, with any benefit at all to fill the space that the o-ring would, with something else other than an oring to get a better seal? Maybe some high-temp gasket maker? Something has to be better than an o-ring.

It's an awkward place to try to feel out and gauge what the tension is on the O-ring. But remember this setup was designed to have an oring. So that's probably your best bet. But I would search around and find a large diameter O ring that fits the parameters. Honestly having never had the leak myself I don't know really what to recommend. But I've seen people revisit this issue a couple of times and it makes me wonder if their head gasket is leaking. People are pretty smart on this forum... I'm amazed that the info people have. I would think you shouldn't have to replace it more than once every 100,000 miles at the worst case scenario. Audi is like your best friend who just slept with your wife. They have this beautiful perfect car but then they fill it with plastic. Which by the way another Forum member informed me it's not actually plastic. It's compressed glass strand fiber, similar to nylon. Which by the way is cheaper than plastic but arguably has a little better heat cycle performance. On other cars I've doubled up O rings. For instance the camshaft position sensor housing on a 2001 Galant has a single o ring sealing it against the head. But I put 2 on instead. But remember aluminum will crack if you over torque it with too many seals over it. I'm not sure if that would work in this case but it's an idea. I think you would have a hard time getting an RTV type sealant on there without smudging it all over the place. But I suppose it's possible it could assist as long as you get it on there slightly setup and a tacky before you put it together and don't smudge it.

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[5ktq]

Yeah, all the black plastic stuff is ~30% glass reinforced nylon 66. Still inferior to metal, except in weight and cost.

[jacobsen]

We're just lucky to have metal replacement parts. The way I see it, if they're not going to do the job someone else will. And they'll make the money for it. That's Audi's loss. My 2001 Galant has no plastic pieces, it's all a hose to port. Nothing to fail or go wrong. Literally all I am hoses still work perfectly.

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[5ktq]

Well, for what it's worth I guess.. my family's VWs/audis with newer plastic connectors haven't had much if any hose, rad, core, etc failures as of yet. (spits over shoulder). I broke a plastic tee on a golf once.

The 5000s I had had no plastic (except the rad) and they ate hoses for lunch. rads broke, heater core I changed 3 bloody times on the one car. Had a few failures on old mk1/2 golfs too, but less than the audis

[ZipMeUpJ]

The first time I changed it the oring was flattened and leaking and the lower heater core connection was broken at the neck right before the hose. second to 4th change were all the oring, but I purchased a whole OEM flange jsut to be safe. Along with a set of premium orings I tried some thicker orings, AND splayed gasket maker around the oring to maybe get an even better seal. But since I made this thread you can guess how that worked out. I think I may have been overtightening the whole assembly.

And by oring I mean the one against the back of the block

[blitz2190]

its not just the oring, if you check the flange against a flat surface I'm willing to bet you can see that its warped. Both the ones I changed were and it causes the oring to then fail after its been crushed flat then lifts back off when the plastic warps.

[5ktq]

Yeah that'd be my guess too. Don't go crazy with the torque, it's only 10nm (7 ft lb!).

Lube the oring with some antifreeze so you don't pinch it, and scotchbrite the mating surface of the head first.

[Willënskraft]

Was there ever a metal coolant thermostat made for the B6?


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[5ktq]

Nope. There is for the same block, but only for transverse ones that don't have the fancy thermostat.

[Spike00513]

Well, for what it's worth I guess.. my family's VWs/audis with newer plastic connectors haven't had much if any hose, rad, core, etc failures as of yet. (spits over shoulder). I broke a plastic tee on a golf once.

The 5000s I had had no plastic (except the rad) and they ate hoses for lunch. rads broke, heater core I changed 3 bloody times on the one car. Had a few failures on old mk1/2 golfs too, but less than the audis

I think my radiator just started leaking. "Plastic end tanks". At least it's not the old Mercedes eco-wiring.
Which I've seen happen on other cars not just Audi, because they also use radiators like this.

Along with a set of premium orings I tried some thicker orings, AND splayed gasket maker around the oring to maybe get an even better seal. But since I made this thread you can guess how that worked out. I think I may have been overtightening the whole assembly.

And by oring I mean the one against the back of the block

The main thing about seals is you don't want to squish them too much and you don't want them to loose. There's a Goldilocks zone.

Yeah that'd be my guess too. Don't go crazy with the torque, it's only 10nm (7 ft lb!).

Lube the oring with some antifreeze so you don't pinch it, and scotchbrite the mating surface of the head first.

Why not use DC111?

https://www.amazon.com/Corning-Molyk.../dp/B002WDU1J8

$5 on eBay

[ZipMeUpJ]

Nope. There is for the same block, but only for transverse ones that don't have the fancy thermostat.

Nope, there's one now for our longitudinal blocks : http://www.urotuning.com/Cooling-Fla...1132E-CAST.htm

[5ktq]

that's not for the thermostat! That was in reply to:

Was there ever a metal coolant thermostat made for the B6?


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[URS4surf]

another issue when trying to get a good seal on the flange o-ring,

if your tensioner gasket/VCG is leaking, it's hard to not get any oil on the o-ring when installing, which will compromise it after a short time...


ymmv

[16vCorey]

Every plastic one I've changed has been warped and had the inner o-ring grove breaking apart. I don't have any experience with the aluminum ones yet, but as long as it's well made and machined, it's got to be better than the stock plastic one.

[jacobsen]

I think someone should find a better kind of seal for that thing. Even if it's cutting out your own from a slab of silicone or rubber.

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[ZipMeUpJ]

Exactly that. I wonder if filling the o-ring pocket with something else will greater a better seal. Silicone sounds good. I may try this route. If it leaks still then I can scrape out the medium and pop in a stupid oring lol.

I'm pretty sure its my flange thats leaking again. Theres no other coolant lines or fittings on the passenger side around the turbo that would leak onto the trans


EDIT: Also the orings that come with these flanges is made of what durometer and material? Would it be smart to then buy an oring thats better resistant to oil from leaky VCs and heat cycling?
I found this webpage about different o-ring materials pros/cons, but I am not sure which material the orings we get are made of. Any one know?
http://www.marcorubber.com/materialguide.htm

[MetalMan]

I'm pretty sure its my flange thats leaking again. Theres no other coolant lines or fittings on the passenger side around the turbo that would leak onto the trans

Well, not entirely true... there is the heater core hose which connects to the bottom of the coolant flange. That hose connector has an O-ring which WILL flatten and leak over time, especially if the coolant flange has been changed a few times.
That O-ring is not sold separately by Audi, but a #211 or 212 size O-ring seems to be a good replacement size (I use #212).

Also, it's possible that heater core hose and/or the the connector itself have become damaged and are leaking.

[jacobsen]

Well, not entirely true... there is the heater core hose which connects to the bottom of the coolant flange. That hose connector has an O-ring which WILL flatten and leak over time, especially if the coolant flange has been changed a few times.
That O-ring is not sold separately by Audi, but a #211 or 212 size O-ring seems to be a good replacement size (I use #212).

Also, it's possible that heater core hose and/or the the connector itself have become damaged and are leaking.

Even more common than the flange going bad.

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