2000 jetta tdi coolant outlet flange leak

tdi-IL

Member
Joined
Jan 2, 2011
Location
central IL
TDI
00' MKIV Jetta TDI - 01M trans & 05' Jetta MKIV TDI 09A trans
My 2000 jetta tdi automatic had a coolant leak from the outlet flange on the side of the engine. Pink coolant gathered on top of the transmission & final drive housing. I found the leak at the outlet flange on the side of the engine's head. I put on a new flange equipped with a new o-ring & put a new o-ring in the temp sensor while going to the trouble of repairing this flange. I filled it with coolant and within a day, the new flange is leaking again. I can see it draining from the unbolted bottom side corner while viewing it with a mirror. VW's design for this flange is bad. Who puts 2 bolts in opposite corners of a rectangular opening on a plastic housing and expects it to seal properly against an aluminum head? I had to say that to feel just a little better.

Anyway, who on this site knows the proper procedure for assembling a new outlet flange? Should I use some emery cloth to clean the aluminum head before installation? Do I apply silicone sealant on the engines head & on the outlet flange's o-ring surface before installation? Am I overtightening the two flange bolts. What am I doing wrong?

Thanks in advance for advice
 

tdi-IL

Member
Joined
Jan 2, 2011
Location
central IL
TDI
00' MKIV Jetta TDI - 01M trans & 05' Jetta MKIV TDI 09A trans
Good Grief! Now I know why no one is replying to my post. I have found that I can not quick reply to any post. I have to do a reply post and then I have to login again each time. What is up with the numerous login request on this site? Someone please cue me in.

I guess since no one is willing to advise me on my earlier post, I will reply to my own post.

My son has a 2000 jetta tdi automatic also. I just viewed his car's outlet flange to find that it is leaking some coolant also. Not bad thought. I can see evidence of small pools of coolant on the transmission housing. It appears that at some time someone put a black silicone sealant around the base of his coolant outlet flange. I plan to follow this procedure and see what happens.
 

tdi-IL

Member
Joined
Jan 2, 2011
Location
central IL
TDI
00' MKIV Jetta TDI - 01M trans & 05' Jetta MKIV TDI 09A trans
Ok. Well its noon and 24 people have viewed my post, yet none have added any advice it. I am somewhat disappointed, but I will charge on anyway.

I disassembled the outlet flange hoses again this morning. Saved about 75-80% of the coolant using a long beak-like visegrisp to clamp radiator hose coming out the front of the outlet flange, then caught most of the coolant draining out of the engine with 1lb cottage cheese containers alternating dumping them into a bigger bucket. You know you are an inexperienced mechanic when you get better at redoing simple tasks :eek: cause you didn't get it right the first go around.

After most of the coolant drained, I cleaned up the outlet flange around its o-ring and the area of the aluminum engine head where it attaches. I then applied a 1/16" film of black silicone sealant engineered for high engine heat areas. I got it reassembled with its two mounting bolts taking care not to over tighten them this go around.

Time to eat lunch. This will give the sealant time to dry. I will post again later to let you know how it worked.
 

gforce1108

Top Post Dawg
Joined
Aug 2, 2006
Location
Newburgh, NY
TDI
04 Jetta GLS BEW, 14 Audi A7 V6 TDI, 13 Porsche Cayenne V6 TDI
That flange was warped on the golf I'm working on. The previous owner had been driving it around with no impeller on the water pump and the heat warped that and the thermostat housing. Not having any temperature problems?
 
Joined
Mar 13, 2009
Location
San Jose, CA
TDI
None
Any luck with the RTV? If you don't mind me asking, was the flange/o ring purchased through the dealer or aftermarket? I typically scruff up the area with a scotch brite pad and make sure its clean, then wet the seal in coolant and bolt it back up. A dab of sealer is always a good idea, but you don't want too much otherwise it will be introduced into your system....by any means, don't go driving around with the leak. Another guy on here thought he could keep driving without problems and locked up the motor :rolleyes:.
 

tdi-IL

Member
Joined
Jan 2, 2011
Location
central IL
TDI
00' MKIV Jetta TDI - 01M trans & 05' Jetta MKIV TDI 09A trans
The black silicone high engine heat sealant did the trick. The leak stopped. I had used some emery cloth to clean the engine head area prior to the initial install. I purchased the new outlet flange OE#038 121 132C(black plastic) from autohausAZ.com. Their parts look to me to be good quality parts. The piece was still in good shape when I took it off to re-seal with silicone. It was not warped from over-tightening like the original one which started the problem. But, I had not left it on that way for over a day.

The metal cast outlet flanges that I have looked into for this fix say that they are for manual transmissions only. Perhaps it may work for an automatic setup? If someone on this site knows that answer, it would be good to know? At any rate for the Automatic trans outlet flange has 3 outlet nipples & 1 sensor o-ring slot; rear-ERG cooler, rear lower angle-coolant sensor slot, very bottom-engine oil cooler, front-radiator distrubtor connector.

I hope this post helps others who see their dashlight for coolant come one, then find antifreeze coolant on the top of their transmission and wander what is happening. This is what happened to me.
 

kipster

New member
Joined
Jul 29, 2007
Location
Highland, Michigan
TDI
2001 New Beetle GLS TDI
I have coolant on top of my transmission and plan to change my outlet flange (038 121 132C) this weekend. Can anybody tell me how much torque to put on those two bolts?
 
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