A/C $1100 Question
 

I have a slow leak in my A/C system. The independent A/C shop thinks its the evaporator. The dealer tells me it has never seen a leak in a 986 evaporator. If any thing, they thinks it's a hose or O-ring. So I'm trying to get some insight into what may be a $5000 repair. Here's the background.

Three months ago, the A/C stopped cooling. The independent filled the system and leak tested it using a sniffer. The shop told me it found a big leak under the dash and the evaporator needed replacdement. It also said the job was too big for because the independent had never taken out a Boxster dash before. The shop said take it to the dealer.

Two months ago, I took the car to a local dealer with a great reputation. The dealer fully evacuated the system and vacuum tested it. It held vacuum for 1 hour with no rise in pressure. Next, the dealer charged the system fully and added dye to see if there was an extremely slow leak that would show up over weeks or months.

The A/C is still cooling fine. But, it makes a periodic wooshing sound now which I told is a sign of a low refrigerant level. I plan take it to the dealer in two weeks to see if the system has lost coolant. The dealer will do this by using a blacklight to look for the dye.

My fear is that they will find that some coolant will have leaked but not see any dye. This would indicate that the problem might be the evaporator. If so, Porsche charges $1800 for the part and 10 - 12 hours of labor. An indepent will take about the same time but charge only $700 for the OEM part. This is a whopping $1100 difference. So here are my questions.

First, are the O-rings between the evaporator and the expansion valve located behind the expansion value and therefore accessible from the front trunk. Or are they under the dash. Given the leak is so slow, I would guess that its a deteriorated o-ring and not a pin hole leak in the metal evaporator. My first thougt is to replace the O-rings and the evaporator.

Two. If the problem is unclear, I am tempted to top of the system using a can of 134a with oil AND stop leak before I shell out $4000 to $5000. Does anyone have any eperience with this, especially with using stop leak?

Three, can anyone suggest how much 134a to add to the system. A Pelican article said the A/C is charged if the pressure is between 25 and 45 PSI. Right now the low side reads 35 PSI. I'm assuming that I should add 134a until it gets back up to 45 PSI.

Thanks for any advice you can give me.

I have the same issue as you. An extremely slow leak. We filled the system with Nitrogen all the way to 20 bar and after a few hours it was still at that pressure, however when filled with refrigerant, most is lost after a few days. We also put dye in the system, and we are unable to find from where it is leaking. I will be trying stop leak today, and recharge the system again, hopefully problem is solved.

Hello Thom.
I will try to answer some of your questions.
First, the leaking evaporator is not such an uncommon issue. I know of at least 3 Boxsters that have that issue (including mine).
First take a look at this diagram:
Here you can see the location of all the O-Rings in the system.

Porsche Boxster Refrigerant Circuit Parts

If to give a direct answer to your first question, there are 4 O-Rings between the evaporator and the expansion valve (2 from each side of the valve). The O-Ring can be reached from the passenger side of the front trunk.
In order to get to it, you will have to remove the nut (Red) and the retaining plate (yellow)

http://986forum.com/forums/uploads01...1348586607.jpg

Now you will have to remove the two Allen screws to get to the other side of the valve.
This is how it looks with the valve removed. In this case the air box is out of the car, but it can definitely be done when the air box/evaporator still in the car.


http://986forum.com/forums/uploads01...1348586671.jpg


With that said, I will find it hard to believe this is your problem.
When I removed the O-rings in my car, they were in perfect condition (after 12 years of use).
If you filled the system with AC dye, it will show pretty clear around the valve (if the leak is there).
It is very easy to detect if the AC evaporator is leaking.
Assuming you still have dye in your system let the AC work for 5-10 minutes when the car is parked.
A puddle of water will show under the car. This “water” is the humidity in the air, accumulating on the evaporator, and dripping down to the bottom of the air box. From there it exits the car thru a draining tube.
If the evaporator is leaking, the water should be contaminated with the dye, which can be detected by using a “black light” flashlight. Another good sign for evaporator leak is the smell of a “cat pee” coming out of the air vents. (I never owned a cat so I’m not sure about that, but that what other people told me)

For the second question.
I’m not sure if the “stop leak” is a good idea. I don’t know if it will stop your leak, and how it will affect the system on the long run. I have to admit that this option has crossed my mind as well.
But after thinking about it, and knowing (or hoping) I’m going to keep the car for a long time, I toke advantage of a rainy weekend and came up with this:
http://986forum.com/forums/performance-technical-chat/36713-ac-question.html

As for the last question, I do not know. I toke the car to the AC guy and he evacuated and recharged the system based on his knowledge and the information he has in his data base.

The all process cost me less then 400$, and I even enjoyed working on my car (like most of the time)
I will be happy to answer any other question you might have.
Good luck.

Meir:

Thanks so much for the detailed explanation. It's very helpful. I'll download the links and perhaps the independent will be willing to tackle the job. Unfortunately, I don't have the space and skills to do myself.

too bad you are not close to me. i would have been happy to land a hand.
on another toght you can ship the car to me. it will cost you less then 5k :D

just kidding. i'm sure you will sort it out if you will find a well skilled AC guy.
the job is not that complicated, just takes a lot of time, and many parts to remove.

Update

Well, the news was good. After driving the car around for a month with the A/C running, the dealer found dye around the expansion valve. There was no dye in the condensate from the evaporator. So, if I'm lucky, I just need to replace the expansion valve and recharge the system. While I'm doing that I will also replace the receiver / dryer because its easily accessible and inexpensive.

BTW: I used BG's Frigi Fresh on the system today and it seemed to work as advertised. The bacteria / mold smell is gone. I'm keeping my fingers crossed it stays that way.

Thanks to one an all for the advice

Greate news. The valve is probably the cheapest part in the system ( except the dryer)