The AC Schrader valve on the high pressure side is leaking. Dealer tells me that this valve is not replaceable, but that it part of the AC hose, and that I will need to buy a new hose at a cost of over $500.00. Is this for real? The only thing that prevents the refrigerant from escaping totally is the little plastic dust cap that screws on top. Obviously this plastic cap is not very effective considering the high pressure.

Can I stop the schrader valve from leaking somehow? Any ideas?

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Dearler is not crazy, Mercedes parts prices are sometimes crazy.
Before spending $500. for a leaky shreader valve, I'd remove the schrader valve core and install a new one on top of the old one, using an appropriate adaptor.
Might cost you $10. in parts and a A/C refill

The problem is that the core of the Schrader valve on this car is not removable. and the Schrader valve assembly itself, although looks like its only screwed into the high pressure AC hose, apparently is also not removable.

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'95 E300 Diesel, 264,000 Miles. [Sold it]

That sounds like a wise way to handle this problem.

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2012 E350
2006 Callaway SC560

Sometimes iti s just dirt..push it in and release it quickly..retest..

I'm a bit surprised the valve core can not be removed....but everything is possible.
Second solution:
Remove the hose.
Have the original valve soldered shut.
Cut the original hose and have a new valve soldered on. Any commercial A/C place can do that. Re-install the hose.
refill system.
I'd try a couple of inventive ways of saving that hose.
I know, I'm cheap

This is the type of valve you need,

Attached Thumbnails

 

not unheard of...some Chevy Suburbans are the same way. schrader valve goes bad, have to replace the entire hose assembly. just did one about a month ago...

as more and more OE suppliers get consolidated, i wouldn't be surprised if this setup exists on other vehicles as well.

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W108
W116
FJ60

Well. I took Arthur's suggestion, pushed the valve in, and released it. IT STOPPED Leaking. I don't think however that I am out of the woods yet. I also need to change my defective, high pressure switch, and for that of course they would need to evacuate and recharge the system. At that point they will be connecting their AC gauge hoses, so the leaking valve may manifest itself again.

Can the system be legitimately recharges without using a high pressure gauge? Also, my rebuilt compressor came with a Schrader valve built-in. Not sure what that its for, but could the high pressure gauge be connected there instead?

One last thing. Can I get away with only one working cooling fan. The second fan is defective.

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'95 E300 Diesel, 264,000 Miles. [Sold it]

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..and just what is wromg w/sw ???

If you were already at AutoZone, why didn't you rent the gauges there? I rented gauges from AutoZone when my personal set were out on loan, so I know they have them. It won't cost you a dime. Charging by sight glass is guessing at best - you really need to know actual pressures before you can further diagnose your high pressure switch problem.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I've always thought that using the sight glass was perfectly adequate. Else why would it be there.

What the system wants is a steady stream of liquid refrigerant coming from the drier, thru the sight glass to the evaporator. The sight glass gives you that info.

Yes, if you are wildly overcharged or undercharged the sight glass can be misleading.

The reason systems with accumulators don't have sight glasses is because there are always some bubbles in those systems. Hence, the sight glass would be misleading in that case and the gauges would be the only way to go.

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2012 E350
2006 Callaway SC560

I have on 3 or 4 occasions "thought" that system charge was correct using the indications from the sight glass, then shortly thereafter discovered that they were way off after hooking up my manifold gauges. In researching both at this site and elsewhere, I have found that I am not alone, and most techs now say the PROPER way to charge is by weight. This is now the way I do it - put the correct weight in, and forget the rest. I still of course do this through the gauges.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I agree that the best way is probably to charge by weight.

However, you must start with an empty system to do that. Most people here do not have the means to evacuate their systems.

Not meaning to be difficult, but in your first post you said "you really need to know actual pressures." In your next post you said to charge by weight.

They are not the same.

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2012 E350
2006 Callaway SC560

>>However, you must start with an empty system to do that. Most people here do not have the means to evacuate their systems.
>>

Many do not realise that some of these answers we give are NOT the best bet way to do things, but they are more geared to the poor diyer guy who can get to charge his own car w/o having state of the art equipment.
Yeah, you can use some common sense and a sight glass. and yeah, retrieving codes with a Radio Shack $2 led is not to be compared to a HHT Benz Scanner...etc . , etc.... but be reminded that many a car get fixed with simple tricks here and that makes up 1/2 of this group..
It's easy to jump on backyard technique as being crap, but there are many a car that get fixed here with them...give me a little info, a few jumper wires and some common tools , and you would be quite amazed at how fast I have fixed many a mechanical/electrical problem, be it a car, tractor, computer, or what have you...
There is a litle Mcquever [ or whatever his name was]in all of us..
Info is the rule...

Okay, you guys are right - everything is relative. For clarification, let me state that there are several ways to determine state of charge. Some are simply more accurate than others. In order, from most accurate to least:

1. Charge by proper weight with gauges attached and thermometer in vent
2. Gauges, maybe with thermometer
3. Sight glass

Again, I say that the sight glass does not tell the whole picture. What if there is an obstruction somewhere in the line causing the pressures to be excessively high? You wouldn't see that without gauges. And if your high pressure switch is defective, you may just be damaging something.

Really, I don't think my suggestion was way out of line. Like I said, Autozone has the gauges for free rental, putting their use well within the scope of the average DIY'er - me included (I am not a pro). With free gauges, there is no reason NOT to hook them up and provide a reading which can only help diagnose the problem further. Now if they have tried to get gauges and can't, that's another story. But telling them to just go by the sight glass when there is a perfectly viable alternative is misguidance in my opinion. Kind of like telling them to measure tire pressure by the bulge of the sidewall - it is somewhat accurate, but why not hook up a tire gauge especially if one is freely available?

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280