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  #1  
Old 11-19-2013, 01:24 AM
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Join Date: Nov 2013
Location: Honolulu
Posts: 47
1983 300SD A/C rejuvenation process?

The second owner of my recently-purchased 1983 SD was, shall we say, not concerned with full disclosure in all areas, and an outright liar about others. The realm I have in mind right now is A/C. About this, he wrote:
A/C works fine and was professionally converted. The system was converted from R12 to R134a by dumping the mineral oil from a new compressor before it was replaced and refilling with synthetic Esther oil. Barier hose was used where needed but most of the lines are metallic. At idle you will not feel the air cool quickly because the boiling point for the R134a is > (higher) than R12. It has been sitting since May and the tollerances on the fittings are not like modern systems so they need to stay wet with the Esther oil (I believe the R134a molecule is smaller than R12) or you have to add R134a at the blue covered, R134a, nipple. (correct me if you know otherwise)
So on the one hand, he wasn't really claiming expertise, but on the other, he's pretty specific about what was done (even if subtly implying that he'd had the work done himself, though receipts prove otherwise.) 1st owner was fairly responsible, it appears from records found in the car. Receipts show he had one shop recharge with R134a (and two days later, another shop checking it to find out what was [still] wrong, I infer leaking) in early 2007. When I test-drove the car (11/2013), entirely on base with installation speed limit of 25 to 30, I detected no A/C.

After hot-wiring the compressor-clutch for a few minutes and getting no evidence of cooling, I verified/discovered that there was virtually no refrigerant in the system - just a puff from the low-side Schrader valve, residual from my own ill-fated attempt to charge without the compressor operating. The compressor isn't noisy. I separate the hoses from it briefly in order to see if any obvious nasty crud came out, and only got dye/some clean-looking oil drops out.

Other observations:
  • no low-pressure cutout switch existed; the leads had been jumped with a new-looking clean wire: I think 2nd owner was shotgunning to try to fix, and gave up.
  • Despite that jumper, other electrical issues (that I will get into in later diagnosis) keep the clutch from ever getting power, short of my providing a hot-lead for my test as mentioned above.
  • There's an unknown dry very-black stain from something near the evaporator (mostly in air-duct above driver's knees, it weeped out near the right edge and stained the carpet a little there)

My plan goes something like this - please critique:
  1. replace accumulator, with new LP cutout and aux fan switches
  2. replace all o-rings but keep existing hoses (no obvious decrepitude there...)
  3. replace expansion-valve - err, that's if someone will tell me it's not an all-day ***** of an affair (?...I've looked at it, and though not a piece of cake, it doesn't look horribly hard)
  4. pressure-test with Argon (it's what I've got handy) to 200psi max - hold for...an hour? a day?
  5. on passing P-test above, evacuate and recharge with R134a (and add oil?)

Should I flush?
Part of me really wants to know about pros/cons of flushing out the whole system, in order both to clean out whatever's there, see if any metal comes out, and to start with a known oil type/qty.
  1. Is that feasible with cobbled-up equipment, i.e. something like compressed air and a means to blow through a flushing agent? (I'm thinking a siphon-gun, say)
  2. Is it advisable?
  3. If I do this, can I add a full charge of oil to low-pressure Schrader valve port?

Been-there-done-that responses welcome.

Mahalo - Dave

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  #2  
Old 11-19-2013, 05:21 AM
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Yes, by all means flush the thing. No telling what oil is actually in there now, you answered this yourself once you discovered the seller was full of it. TXV on a W126 is not that bad, it is a pain but doable within an hour if you have the proper tools. Crows feet and line wrenches that fit a ratchet. Take your time reinstalling it and do not cross thread the fittings. You need to have them all threaded a few turns before tightening it or it will never line up.

I would not use 134A, but it is your car. R12 cools far better in these. I suppose if you went for a parallel flow condenser you would have decent vent temps. No experience there, sorry.

Oil goes in before the charge. Mineral is R12 only (BTW, I have not bought a 'new' compressor recently that was full of mineral), PAG 134A only, Ester seems to go both ways just fine...Esther is a woman's name.

Verify all the vacuum pods work, the three behind glove box can be swapped in about 30min and cause many of the issues such as defrost only, poor vent temps due to no recirculated air, etc.

Later SDs had a better condenser, smaller water pump pulley, and upgraded fans (clutched and aux)...these all improve vent temps at low speeds/idle. BTW, the M116/7 fan with clutch off a 420/560 fits, should be the same off a 380/500... those fans move way more air and probably cheaper than finding a late SD fan with clutch.



I highly recommend dumping that GM R4 compressor and going with a Sanden conversion. Best thing I ever did for my SD. It was $200 plus the cost of compressor and building a few hoses.

If you are uncertain of the condition of your R4, do not take the chance. Made that mistake on the 560 with the Denso on there as it worked, rebuilt it all, etc. Compressor body leaks. It is the original from '91 though, so no one to blame but me.
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'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
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  #3  
Old 11-19-2013, 06:02 PM
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Quote:
Originally Posted by Hit Man X View Post
Yes, by all means flush the thing. No telling what oil is actually in there now, you answered this yourself once you discovered the seller was full of it.
Do you know of a non-exotic-tools method of doing the flush?

Quote:
Originally Posted by Hit Man X View Post
TXV on a W126 is not that bad, it is a pain but doable within an hour if you have the proper tools. Crows feet and line wrenches that fit a ratchet...
I've been looking for an excuse to add those tools to my inventory - yep, I saw what you mean; the TXV is in a sort of horizontal "well" up above the pedals, where there's no human working-position that is comfortable. But I've got a new valve on hand so... okay, I will do it.

Quote:
Originally Posted by Hit Man X View Post
I would not use 134A, but it is your car. R12 cools far better in these. I suppose if you went for a parallel flow condenser you would have decent vent temps. No experience there, sorry.
Jeez, I'm afraid to even look for R12. If it's got to be purchased from outside my island, it's automatically going to be huge $$$ due to hazmat transportation charges. I suppose there are A/C shops that sell it after reclaiming...? (I'd been wondering about going with the Next Big Boondoggle, Puron, but I've already got too many variables.)

Quote:
Originally Posted by Hit Man X View Post
Esther is a woman's name.
Yeah, I liked that, too. I was once after a girl named Esther, until I found out she was already living with another guy. From that day forward, she was thus dubbed 'Polyesther.'

Quote:
Originally Posted by Hit Man X View Post
Verify all the vacuum pods work, the three behind glove box can be swapped in about 30min and cause many of the issues such as defrost only, poor vent temps due to no recirculated air, etc.
That reminds me of a really annoying (but predictable) finding from my poking around in the evaporator box: I think probably ALL of the vinyl foam "door" seals in my system have turned to that nasty-sticky dust. I can't imagine an easy remedy for that, and was prepared to just blow/vacuum it out and live with the leaks...but do you know of a reasonable fix, short of extracting all the air-handling components and gluing in some closed-cell neoprene? Does someone sell a retrofit that's not the same crappy open-cell foam?

Quote:
Originally Posted by Hit Man X View Post
Later SDs had a better condenser, smaller water pump pulley, and upgraded fans (clutched and aux)...these all improve vent temps at low speeds/idle. BTW, the M116/7 fan with clutch off a 420/560 fits, should be the same off a 380/500... those fans move way more air and probably cheaper than finding a late SD fan with clutch.
Quote:
Originally Posted by Hit Man X View Post
I highly recommend dumping that GM R4 compressor and going with a Sanden conversion. Best thing I ever did for my SD. It was $200 plus the cost of compressor and building a few hoses. If you are uncertain of the condition of your R4, do not take the chance. Made that mistake on the 560 with the Denso on there as it worked, rebuilt it all, etc. Compressor body leaks. It is the original from '91 though, so no one to blame but me.
Hours later, I've seen a bunch of your posts mixed in with the Sanden conversion-related threads on this forum. Def looks like the way to go, and it looks like these mods do perform OK (or even startlingly-well) with R134a, too. I've asked for pricing from Rollguy & the Klima website. Thanks for nudging me in this direction - I'm all about getting it right the first time...

--Dave
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  #4  
Old 11-19-2013, 11:34 PM
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Posts: 9,087
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I did my first flush using that ~1 quart sized metal can. Pain in the ass like no other, I bought this thing as I have so many old vehicles it just made sense - Flush Gun - Copyright 2008 Hecat

TXV... best for me is to have the car up on ramps or jackstands up front. Then I can kneel beside the door and stuff my body in there. Removing the steering wheel would help too.

Ah, I did not realize you are in HI. R12 sells for about $25/12oz can here in Texas or about $300 for a 30lb tank. How much of a penalty is there to ship it there? I believe 134A with a parallel flow condenser, aforementioned fan+pulley upgrades, and a Sanden would work well. Just no clue how volatile the climate is there, I am sure humidity is there like when I am in Houston for extended periods of time.

Never thought about replacing that foam business. If you figure it out, I am sure we would like to know!

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
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