Some A/C advice needed -- leaking valve stem - PeachParts Mercedes-Benz Forum

ps2cho · #1 08-04-2011, 12:29 PM

I noticed about 3-4 months ago when checking pressures, that after I disconnected my gauges, the valve stem was hissing on the high side. I tried pressing it in thinking maybe some dirt was clogging, but no luck.

Yesterday I got out of the car and heard heavy hissing -- well looks like the high side valve cap blew a hole through it and now my refridgerant is low.

Any ideas on process I should take to try and repair without having to evac or do I not have any options other than evacuation?

And IF I do evacuate, would you recommend I replace R/D for preventative maintenance? I'm not even sure if it was replaced when the car was converted from R12 to R134a. One day when I rebuild system (evap/compressor), I'll backconvert, but I'll keep it simple for right now.

A side note too -- I was seeing over 300psi on high side during hot days (110F)...I was recommended to "soak" condenser coil -- how can I soak it exactly? Or is the cleaner some sort of foam?

boneheaddoctor · #2 08-04-2011, 12:57 PM

You need a new schrader valve and yes...the system will HAVE to be evacuated before recharging because

#1 you need to get the air out....its non-condensing...and

#2 you NEED to get any moisture out.....

You really are supposed to replace the receiver dryer anytime the system is opened but that means you need new o-rings and need to replace that part of the oil.

However given the small size of the opening you can get the old one out and the new one in quickly enough you might get away with just evacuating and recharging.

Now there is a tool that will allow you to replace the shrader valve insert without losing the charge..if you know any HVAC guys...maybe for a few bucks you could get him to do it for you if they have one of those.

Legally, you have to have a recovery machine to suck the system dry before you do any work or you risk the enviro-nazis from coming over and doing unspeakable things to your nether regions. Because its illegal to vent refrigerant into the atmosphere.

vstech · #3 08-04-2011, 01:01 PM

on a converted car, it's impossible to remove the schrader without first removing the 134 adapters, and they often are locktited in place if you attempt to remove the schrader I recommend first getting heat and warming the adapter well, then gently removing it, THEN get the tool to remove the schrader without dumping the charge...

ps2cho · #4 08-04-2011, 01:08 PM

Gotcha. Sounds like evac is necessary. I'll have a shop recover the leftover refrigerant, i'll go and buy a vacuum pump (I need one to do my 260E soon anyway), replace R/D and both sensors, replace schrader valve then pull vacuum and recharge with correct amount.

Anything else I should do or check with the system open?

Would this pump pull enough vacuum for the job?
http://www.harborfreight.com/automotive-motorcycle/refrigeration/25-cfm-vacuum-pump-98076.html
It says 2.5CFM Pump pulls 75 micron/10 Pascal maximum vacuum.

tangofox007 · #5 08-04-2011, 01:11 PM

Quote:

Originally Posted by vstech

... THEN get the tool to remove the schrader without dumping the charge...

On an already partially discharged R-134a system, the tool will cost more that the refrigerant is worth. And, in some cases, there isn't adequate room to use the tool, especially on the high side valves.

vstech · #6 08-04-2011, 01:13 PM

nah, the 1/4 sae tool is only about 12.00

however, ANY volume of R134 has zero value in one of these cars that's been converted...

boneheaddoctor · #7 08-04-2011, 01:23 PM

Quote:

Originally Posted by vstech

nah, the 1/4 sae tool is only about 12.00

however, ANY volume of R134 has zero value in one of these cars that's been converted...

AH.....BUT the use of the tool will negate the need to evacuate the system as it would not have been opened to the Atmosphere. Saving hours of time with a vacuum pump.

ps2cho · #8 08-04-2011, 01:47 PM

Time is not the issue -- I just want to do it right.
I actually have 2 weeks PTO from work right now

ps2cho · #9 08-04-2011, 07:18 PM

Question -- (unrelated to 300TE) Do the R12 valve caps not depress the valve stem when screwed on?

tangofox007 · #10 08-04-2011, 07:28 PM

Quote:

Originally Posted by ps2cho

Question -- (unrelated to 300TE) Do the R12 valve caps not depress the valve stem when screwed on?

They should not.

ps2cho · #11 08-04-2011, 07:49 PM

OK -- just checking.

300TE has been under vacuum for about 1hr, just disconnected fitting and watching to see if there are any drops in vac for 15mins or so, then its time to fill again.

900g for w124 correct aka 32oz of r134a / 3 cans right?

tangofox007 · #12 08-04-2011, 07:55 PM

Quote:

Originally Posted by ps2cho

300TE has been under vacuum for about 1hr, just disconnected fitting and watching to see if there are any drops in vac for 15mins or so, then its time to fill again.

Disconnected the fitting?

Quote:

Originally Posted by ps2cho

900g for w124 correct aka 32oz of r134a / 3 cans right?

The general rule seems to be to use 80-85% of the R-12 capacity when installing R-134a in a R-12 system.

ps2cho · #13 08-04-2011, 07:57 PM

I meant the gauge adapter sorry.

Also -- should I put 2-3oz of oil in for anything lost during evac?
R12 was 1100g according to specs...
Why does the FSM shows 1000g instead of 1200g -- so 91% less?