Rplacment AC low pressure connection - PeachParts Mercedes-Benz Forum

GDC · #1 06-08-2009, 01:26 PM

I did a search, but didn't come up with any hits. Maybe I used the wrong search terms.

My 1993 300E has developed an AC leak and it seems to be coming from the low pressure connection. I put in dye and the only place there is any indication of dye is at this connection and the dye is allover this area of the car it. It seems like there is more dye than I put in.

I pulled a vacuum on the system and it held for over an hour so I am pretty sure that this is the only leak point. Originally, I thought I could simply replace the valve stem, but neither of the tools I have will fit over the center pin in the valve. Does the whole fitting have to be replaced or is there some trick to getting the stem out.

The car has factory R134.

Thanks

mramay · #2 06-08-2009, 01:56 PM

The Nippondenso compressors on my '87 560SEL and '87 560SEC both developed leaks where the hoses connect to the compressor. Six o-rings for each fixed the leaks and it was a DIY project.

What kind of compressor do you have?? The stem is the same as a tire valve so a auto parts store tool will remove/replace them.

GDC · #3 06-08-2009, 02:12 PM

I'm not sure what the compressor is, but given the fact the it will hold a vacuum and that the dye loss was centered on the low pressure fitting with an increase in concentration up to the fitting, I'm pretty sure that the compressor seals are okay. I tried two different tools on the stem and niether of them would fit over the center pin. if you look down the bore of the fitting, you can't see the crossbar that the valve stem tool catches for removal / installation. I'm not sure if this one has a replaceable stem, the top kind of looks like a ball bearing..

gmercoleza · #4 06-08-2009, 02:40 PM

If you say the car has factory R134a, it does not use a standard schraeder valve like those used on tires. I don't think a R134a valve stem can be replaced the same way; on my wife's van, when the valve started leaking, they had to replace the entire line since they said the valve was not repairable. Thankfully the repair was done under warranty.

GDC · #5 06-08-2009, 05:12 PM

I was afraid of that. This ones seems to be screwed onto the AC line, so hopefully it is replacable. When i do a search on the online parts sources, I keep getting refered to the tire stem type for this car. Out of curiosity, I ran a search for the same part on my 94 E320 and got referred to the same part.

Benzmeister · #6 06-15-2009, 12:21 PM

I had to replace the entire line to the tune of $300 plus, included hose and fittings. These hoses seem to be very expensive.

gmercoleza · #7 06-15-2009, 12:23 PM

FYI you can also have a qualified A/C shop fabricate a new line for a fraction of the cost - they will just use the connection ends of the broken line.

Matt L · #8 06-15-2009, 12:51 PM

How about just using a good cap with an o-ring seal? Service fittings are capped not only to keep them clean. It is also to prevent leakage.

GDC · #9 06-15-2009, 01:25 PM

I got a new cap with a new seal and put it on yesterday. I didn't have enough R134a to completely refill the system, but I got enough in to blow cool air. I figure if it stays under pressure for a few days, I should be good to go.

I also found a site online selling 12 oz cans for $3.99 each. This sure beats Walmart's $10.97 price.

I expect to be able to fully charge the system in a few days.

Matt L · #10 06-15-2009, 02:15 PM

10.97 for 12 oz is out of line. It's 4.50 at the local Car Quest place, and $90 for a 30# can.

Be sure that what you're buying is pure 134a, without any snake-oil additives.

Benzmeister · #11 06-15-2009, 04:31 PM

Quote:

Originally Posted by gmercoleza

FYI you can also have a qualified A/C shop fabricate a new line for a fraction of the cost - they will just use the connection ends of the broken line.

I did find out this latter. But a good AC shop around here is hard to find.

ps2cho · #12 06-15-2009, 09:12 PM

Walmart by me sells 12oz R134a for $6.50 a can.

bolomiester · #13 06-15-2009, 09:24 PM

Quote:

Originally Posted by GDC

I got a new cap with a new seal and put it on yesterday. I didn't have enough R134a to completely refill the system, but I got enough in to blow cool air. I figure if it stays under pressure for a few days, I should be good to go.

I also found a site online selling 12 oz cans for $3.99 each. This sure beats Walmart's $10.97 price.

I expect to be able to fully charge the system in a few days.

Great price! Do you mind sharing your source? I'd love to have case on hand.

samiam44 · #14 06-16-2009, 10:09 AM

Shrader valves are replaceable- even with the system full. NAPA etc sell them or there is always the dealership. Only a few $$ to replace the valve and it is a common leakage point.
Hoses are rebuildable.. if you need a hose. If you open up the system, consider putting in a new dryer and adding an ounce of oil.

M

Arthur Dalton · #15 06-16-2009, 11:00 AM

The service valves on 134a are not the tire type valves as R12 uses.. They are BALL check valves .. The most common reason they leak is dirt/debries gets on the surface of the Ball.. an easy remedy is to charge the system and then turn the car OFF so the low side pressure comes up to equalize.
Higher the ambient , the higher the pressure will be.
You then take a small dowel of wood and push the ball in a few quick jabs.. The refrigerant you release is under high pressure and that will clean of the ball and allow it to fully seat. Then put the cap back on.
I have fixed many a leaking charge port valve in 2 seconds by simply pushing the ball in once after a charge to make it seat.................

I do this with all valves, even R 12 type and tire valves. It is the inside pressure that helps seal the valves.

Ever notice a tire leak at the valve stem and all you had to do was push the valve pin IN once and the leak stopped ????
Same deal.............................
And you know how you spit on the tire valve to make sure that is not leaking....well, you do the same on the R valve, but you just use a little refrig oil..if they leak, you will see it in the air bubble from the oil you covered the valve ball with............