So I filled up with R134a (converted system about seven years ago, done properly, all seals, new compressor, replaced expansion valve), the car sat for a week as I redid the fuel sending units (new check valves, new filter, new accumulator, etc), and as I drove the car I realized I had no A/C.

So this morning I shot in another can of 134a, and a can of dye. Started looking around all of the usual suspects, but could not find the leak. Below the dash - no trait. So not the expansion valve. Around the compressor - nothing. Around the receiver/dryer - nothing.

So I shrugged a bit and fished out the blue valve cap that goes over the low pressure outlet valve. Except that valve was neon yellow. In fact, everything around it was neon yellow. As looked closer at the valve, I saw bubbles of yellow doming out of it! And yellow, like lava, was dripping around everywhere!

Obviously I am in luck - if you want any part in the A/C to fail, this is the one. Cheap, and easy to get to.

But technically, this would be cracking the system open. I would have to vacuum, and all that, And replenish the oil. No problem - I can do that.

Now I have a question: Would this also mean replacing the receiver/dryer (I have a spare)?

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

Nope. Since the system was still holding pressure then moisture wouldn't have entered the system. Evacuate, replace the valve, vacuum and re-fill. Buy a lottery ticket while you're on a streak!


***Begins popping the corn and getting comfortable***

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

I'll see about that powerball ticket...

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

The following product will let you change the valve core without you having to evacuate the system. The freon loss is bare minimum - less than that you would when removing A/C charging hoses.

Amazon.com: Mastercool (MSC81490) R-134a Valve Core Remover/Installer: Home Improvement

I used one to replace the valve cores on my '86 300E with R12 - was a 5 minute job. It's well worth the investment.

Make sure you use nylog or similar on the threads of the replacement valve core to prevent leaks.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

I've got a 134a conversion on mine, so I wonder if this tool is the right size. I read on Amazon that this thing really is for US made 134a systems, and that foreign cars have larger valves.

So, (1) the Benz is foreign, and (2) my valve is a conversion valve.

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

MasterCool's web site lists various tools for the various sizes. You might want to check the size of your schrader valve and purchase the appropriate tool.

As I said earlier, mine was R12 and required a different tool.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

On topic of A/C: I just ordered the CoolerMaster tool and their selection of cores, so I am going this route. Still 100 bucks all together, but I don't have to pay someone to reclaim the R134a.

On topic of luck: On our Audi TT convertible, the rear window was falling out (common problem, general solution: new top about 2.5 to 4 grand). I had figured out a complex re-glue job, with somewhat success, but not perfect yet. I was going to have to do more work on it.

This morning I went out to get the car, and someone had sliced the top! It was parked a block away, and the neighbors heard the alarm go off early in the morning. Because of the alarm whoever did it ran, so nothing was stolen, and there was no rain. When I saw the damage, all I could think about is the low deductible on our policy....

Off to buy that lottery ticket...

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)