1997 Passat Glx Vr6 -thermo Housing Leak -07/28/04

[santoluzbel]

Hello, Everyone, I've just signed up to the forum to bring questions as well as solutions to some of the problems of this car model. I will answer promptly and with all my knowledge or suggestion for a solution, and my email address is available for direct communication as well. I am not a mechanic, but have worked on my cars for a long time, often with the aid or under the guidance of professionally trained mechanics I trust. So that's the base of my humble knowledge. I have had this car for about three years; bought it used from the original owner, with all the repair and maintenance records. I live in the San Francisco Bay Area, where weather is generally in the 60s, but oscillates year round between 45 in the coldest part of winter to about 92 in the hot summer.

Overall, I like the car's handling and its comfort, too. However, i've had some consistent problems with this car:
1. "Check Engine" light forever ON
After many, many trials and many more errors, I discovered that the key here (as many of you have signaled in a few postings) is the propensity of this model to pull code errors. Having realized that, first thing to do is take the car to someone with a computer reader to see what codes are coming out. Then, through a process of elimination, arrive at the source(s) of the light being ON.
2. Locks
Sometimes the rear door locks do not lock, or stay unlocked even after the remote or the key have been used. I am still investigating this problem. I believe the source is a misaligned part in the lock assembly, but am not sure.
3. Power Windows
The front windows stopped working within two days of each other, apparently for different failures, according to the noises heard. A mechanic friend tells me the research will reveal whether it is the plastic dollar-fifty white brackets or the plastic arms or, simply, the motors.
4. A/C
Sometimes it works beautifully, sometimes not at all. Throughout its life, this car has had this problem. It is expensive to solve it, so I have not done much about it, but it's in the list.
5. Thermo Housing Leak
This is the most common problem in this car -and the reason for my writing and consulting with you: it was repaired twice in 4 years before I purchased it, and in my experience it has happened twice as well, the last time one year ago, the most recent about 1 month ago. Each time the leak came from a different part of the thermostat housing.
The previous time I did the repair under guidance of a mechanic friend and the VW Official Repair Manual ($150, new -I borrowed it from my friend and made xerox copies of the most common sections and those which I could work on with the tools I have -so not a full manual). It lasted a bit over one year.
The problem seems to be that the entire housing assembly is made of a hard plastic which, over time and use, warps.
The second time, just about a month ago, I bought the parts and did the replacement myself as well. I replaced it a week ago.

Here is what I did:
-drained system from bottom hose plastic bolt;
-loosened all hoses attached to housing;
-loosened bolts;
-removed thermo housing;
-inspected leak source;
-cleaned engine block section where thermo housing attaches with a soft wire brush and a clean rag to remove coolant gunk and o-ring remnants;
-assembled replacement housing, replacing thermostat (70c) and sealing parts with Permatex thermo housing sealant, thinly coating the o-rings with dialectric grease and the bolts with anti-seize; reused the same sensors;
-attached housing to engine block, sealing it with Permatex and bolts w/ anti-seize;
-tightened bolts to 10Nm torque;
-let car sit for 24 hours to cure the Permatex;
-filled system with new coolant mixture of G12 A8 and water at 40%-60% ratio depressing top radiator hose and topping with engine on until fans went on.

The leak clearly comes from the smaller bolt, the one further deep and recessed towards the passenger cabin.

I suspect:
1. bolt broken,
2. new housing warped,

So, here is my question: Any clues as to why it is leaking still -and rapidly?

Many thanks for whatever suggestions you may have.

Santo

[boschmann]

Did you replace the o-rings on the sensors? I've not had good luck trying to reuse them.

[santoluzbel]

Yes, Boshman, I did replace the o-rings on every one of the three sensors. Thanks for the reply.

[santoluzbel]

Sorry about my misspelling your name, Boschmann.

[boschmann]

I've had my share of problems with those plastic housings, but never that bad. Could the o-ring have slipped out of position? Could the metal housing have a crack at the bolt threads? It sounds like you'll need to go back & reinspect it all.

[santoluzbel]

Originally Posted by boschmann

I've had my share of problems with those plastic housings, but never that bad. Could the o-ring have slipped out of position? Could the metal housing have a crack at the bolt threads? It sounds like you'll need to go back & reinspect it all.

Weel, I had to go back and re do the entire job, and found that, as you suggest, the o-ring had slipped out of position and was chewed up. Got new o-ring and replaced it, this time w/o the grease. It has been one week and no more problems.

Thanks very much for answering my query.

[ducttape]

dont try to reinstal without thermostat. this is part of the spacer that holds the o-ring to the flange. and O-ring on top off thermo.

[cougar1987]

If it looks like it leaks again from the bolts try some LIQUID TEFLON instead of anti-seize.