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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old June 20th, 2007, 08:19   #1
bigblue
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Default most likely areas for AC refrigerant leak - B4 passat

I bought the car without working Air conditioning. I put in 2 lbs of r134a and was pleasantly surprised that the system cycled well with the prenotion that it has a leak. I gave it the old "soapy water in spray bottle" test whever I could imagine under the hood but didn't find any bubbling patterns

That was about 3-4 weeks ago and it just started to cycle less and less as expected. I could keep adding r-134a but I'd rather start looking harder for the leak and find the root of the problem.

Where are the most common areas of a B4 passat A/C system to leak refrigerant? Are there any particular o-rings or hoses I should pay more attention to? Are condensors or evaporators common to leak on these?

I have a UV light and I can see the dye is in the system but I've never had much luck with those systems.


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Old June 20th, 2007, 09:07   #2
rdkern
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My experience is that it leaks where you last did work! Not very helpful, I realize, but do check the expansion valve (you need to take off the plastic "case" around it to get to all four lines), the compressor itself, and the drier. I didn't have problems with the radiator portion, but that's possible too.

So, you have two seals at the evaporator (in the cabin, not fun to get to), four at the expansion valve (no big problems, have a "magnet on a stick" handy to pick up the dropped screws), two at the compressor, and two at the heat exchanger. I'd start at the expansion valve (40% of connections at one fairly easy to get to spot).
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Old June 20th, 2007, 19:09   #3
CaptainKirk
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My A3 had a leak in the low pressure line. The rubber section of the line developed a bubble and 2 small leaks (Not a cheap part to replace).
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Old June 21st, 2007, 04:46   #4
bigblue
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Quote:
Originally Posted by rdkern
... I didn't have problems with the radiator portion...
the condensor?

Quote:
Originally Posted by rdkern
So, you have two seals at the evaporator (in the cabin, not fun to get to), four at the expansion valve ... two at the compressor, and two at the heat exchanger. I'd start at the expansion valve (40% of connections at one fairly easy to get to spot).
That's a good idea. The expansion valve is underneath the airbox/flapper/cabin filter right? How much under the dash board must be pulled out of the way to access the evaporator seals?
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Old June 21st, 2007, 08:48   #5
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Expansion valve is in the engine compartment, right in front of where the passenger sits. Find a plastic-covered box with two metal tubes going into it. Take the plastic off, and you have the expansion valve right in front of you, with the two from the engine compartment right there. The two others are on the back side of it, and I believe are accessable at the same time.

Radiator.. condensor... whatever. Yes that's what I meant, just don't always remember the correct wording.
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Old June 21st, 2007, 20:37   #6
KarlM
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Diagnosing the A/C system is only one step removed from voodoo. My '97 A3 has been serviced several times but the same issue reoccurs: every time the car is parked for a week or so when I'm on vacation the system loses its charge. There must be a seal that dries out and shrinks when the A/C isn't used letting the refrigerant escape.
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Old June 22nd, 2007, 09:10   #7
rdkern
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Probably at the high point of the system where the oil may not hang out - the expansion valve. You might consider replacing those seals (4 different sized gaskets. Of course, an evacuation and refill will be necessary. If you do this, make sure to oil the gaskets before putting it together. Makes all the difference.
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Old June 22nd, 2007, 18:19   #8
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Quote:
Originally Posted by rdkern
...make sure to oil the gaskets before putting it together. Makes all the difference.
I don't know am I right or not (I think I am), but, isn't better to grease the gaskets? I know why greasing is better, but, sigh... to complicated (for me) to explain.

Last edited by LLL; June 22nd, 2007 at 18:21.
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Old June 23rd, 2007, 09:03   #9
rdkern
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I purchased some of the ac oil and used it (yes, it's florescent). Grease might work, just don't know if it will have any issues with the remainder of the system. If there are good reasons for one over the other, please let us know. I strongly believe that something should go on them - putting them on dry seems to be asking for issues.
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Old June 23rd, 2007, 10:28   #10
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I don't know about the others, but I always use grease. Oil is very "thin" liquid comparing to grease (I know, grease is not a liquid, but whatever...). After installing the gaskets with grease, the grease goes kinda of "drying" (air, temperature of the engine, tightening), which hermeticaly close places where gaskets are installed, which means, no liquid, no air licks wil be noticed (depends of the correct/incorrect installation, right?).
Silicone gel is another solution for gaskets, by my oppinion, also better than oiling.
If I'm wrong, please somebody correct me.

Last edited by LLL; June 23rd, 2007 at 10:32.
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Old June 25th, 2007, 07:14   #11
EtherNut
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The stuff you want to use to seal the AC lines and Orings is called Nylog.

Find it Here:

http://www.ackits.com/merchant.mvc?S...ory_Code=Nylog

They'll have about everything you may need.

Ackits.com has a very helpful forum community as well.

The Ether..
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