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#16
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THE PLOT THICKENS!
I just hooked up the gauges again on both low and high sides. With the car off, I was getting about 110 PSI at both. At idle, the low side bot down to about 80 and the high side to 140-150ish, but when revving it, they only got to about 60/180ish. This is wierd, its like the compressor just isn't putting anything out or the expansion valve isn't providing resistance. The expansion valve is brand new, though. What gives? Should I take the freon out and clean and reinstall the old expansion valve (which is specifically labeled for R-134 - the new one isn't labeled either way)? What would cause this?
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#17
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Okay, it seems that I have a bad or R-12 expansion valve (or so the current theory is).
I have this expansion valve: http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=23O1DEH0V23O1DG127&year=1984&make=MB&model=300-DT-001&category=All&part=A%2FC+Expansion+Valve Is this for R-12 or R-134? from what I'm getting, I think it's r-12.
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#18
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Quote:
That seems awful high. What was the outside temp at the time, and how much freon did yall install into the system? **edit** Well, somehow I missed post 11. So you have 3 12 oz cans of freon I take it? I'm gonna cut you some slack cause you are young and learning, but your dad should know to flush the system, replace o-rings, install your parts, pull a vac, check for leaks, resolve any, pull another vac, allow that vac to draw in your first bit of freon and charge up system. Your problem that it is going to be hard to deal with, is the lack of a flush, and the unknown items that was in the system. With those new parts you installed, who knows if you clogged up your exp. valve? If system is reopened, you then need another rec/dryer. Then oil, freon, yada yada yada...... You simply can't take all those shortcuts, have issues, then expect very helpful answers from us because we have NO IDEA! Too many variables....... This will be a very good learning experience for you though. One you can pass on to others in the future.
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Jimmy L. '05 Acura TL 6MT 2001 ML430 My Spare Gone: '95 E300 188K "Batmobile" Texas Unfriendly Black '85 300TD 235K "The Wagon" Texas Friendly White '80 240D 154K "China" Scar engine installed '81 300TD 240K "Smash" '80 240D 230K "The Squash" '81 240D 293K"Scar" Rear ended harder than Elton John Last edited by JimmyL; 06-05-2007 at 12:02 AM. |
#19
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In my defense, the o-rings did get replaced and we did everything you listed there except a flush, which I said we should do. My dad's response was that the receiver drier should filter any leftovers out, and that he had never had a problem with that sort of thing in the past. He did flush it thoroughly when he converted it, though.
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#20
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Guide
I may be a little late in this, but Diesel Giant has a nice pictorial on what you are doing. repairyourac.htm
I just completed mine, with a complete flush, then had a home ac guy help me with a nitrogen pressure test, then he pulled 31" of vacuum (almost a complete vac). We weighed out 2.2 lbs of -134. Now I just need to tighten the compressor's belt a little more. Good luck
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Mercury is a boxer 1984 300d 1999 Prelude Medici road bike Klein touring bike Klein mtn bike |
#21
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Okay, another update.
Ironically, it seems that something HAS taken out part of the compressor, but it's not leftovers from the failed one. When I was installing the expansion valve, the guy I bought parts through supplied an O-ring kit. The O-ring for one of the lines was too big, and a chunk was cut out of it while I was installing. It was on the top right line. (I thought I knew where that went, but I seem to have forgotten). It was easily retrieved by blowing some compressed air into the system (after which I installed a new expansion valve with the RIGHT O-rings, vacuumed it, charged it, fired it up). It will fire up, the compressor seems to work, but I'm still not getting enough pressure differential for good cooling. It seems the compressor is just not compressing enough. This leads to my question, are there screens anywhere in the system, or would the O-ring chunk have gone through the compressor? This is more of an autopsy than anything else, but are there any? I'm thinking of getting a Behr OE rebuilt compressor or taking apart the current one and trying to find if there's a seal somewhere or something repairable that's causing the trouble. Anyone have any experience in trying to reseal these things? Any suggestions as to how to procede? The compressor doesn't seem mechanically dead, there just seems to be a bad seal somewhere that is keeping it from performing.
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#22
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Possibly a reed valve in the compressor is broken from the foreign object and cannot seal on compression therefore not providing enough pressure differential (what you have). Too much oil in a system can blow a reed valve on an R4, also.
No filter screens typically on MB systems, unless added by P.O. aftermarket. If the washer was the one for the low side (larger line) then it hits the compressor. If it is the high side washer, the piece would probably be in the condensor.
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The Golden Rule 1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later) |
#23
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Well, I'll be putting one in after all this is done because I really don't want to have to go through this again. This has been the job from hell, going out into the 90* Texas heat to fix the A/C.
Anyway, is there any way I could replace the reed valve? Should I haul it to an A/C shop and have them replace it?
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#24
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I don't know that the reed valve is the problem. Just one of the "usual suspects" (from the movie, Casablanca ).It's inside the compressor anyway and not a DIY job and one very few shops would do (at least economically). A new or remanufactured compressor takes care of that.
GM had a TSB several years back about putting in a suction side screen. A smart GM parts man should be able to fix you up.
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The Golden Rule 1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later) |
#25
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Well, we gave up on that compressor... it ran, but not well enough for any sort of effective cooling.
Here we go again, my dad just bought another R4 for $200 from a local O'Reilly's. I have at least managed to talk him into a new inline filter. We know the exp valve is fine because we put in a new one after the compressor start having problems. I dunno about the dryer, my dad will prolly want to leave it, is it worth replacing? I'm gonna try to get him to do a full flush this time, my main point being that without a flush, we have no idea what to do in the way of oil, and if we put in too much oil, the new compressor will do what the old one did. Would the oil have gone out with the refrigerant? If it is carried in small particles by the refrigerant, I guess it would be fine, but otherwise..... Also, I'm looking up where to find an In-line filter so we never have to do this again. So far the only mention I have found is to call an A/C shop (Compressor just seized 82 300TD) That would work for us, as we are in Texas, but is there any place we could order them online? Searching for like 20 minutes gave me nothing there. (*chuckle* just noticed that LarryBible has 9,999 posts. Just one more...)
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#26
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*bump?*
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#27
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Read my posts here for online suction side screen: R4 Compressor Siezed.....
Go to a GM parts counter (Pontiac for sure; others most likely as well) and for ~ $2 or $3 they should hook you up. There are suction side filters, but they're larger and require some hose rebuilding skills. Here's a high side filter (if you like high side filters) that gets good reviews: http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=inlinefilters
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The Golden Rule 1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later) |
#28
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Okay, another update. I seem to be learning a good bit about A/C from this.
We went and picked up the new compressor - it's the same adaptable GM one we had before, but this one appears to be made in China. While at O-Reilly's, we got another 8.5 oz can of Ester (I've been carefully avoiding the oil charge canisters), as well as a large container of Interdynamics system flush. Now theres just the problem of my dad's concept of flushing. Is a flush gun the best way, or should I follow my dad's ideology of just getting the flush to flow through the lines somehow? I don't see how the speed would make an incredible difference, it would be hard for anything to wedge in there really well. That may be useless, he may have a flush gun of some sort somewhere that he intends to use, or he may have some crazy way he does it with his air compressor (he does everything with that thing, its kinda scary). Also, I did check out that thread and article about the screen, and it seems we will have one.
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1984 300DT turbo 138k mi Still hauling me to school and back. Handy Site: http://www.dieselgiant.com/ |
#29
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To properly flush the system you MUST pull every line loose and flush in sections. Blow the flush out with compressed air, repeat. Drain any condensate from your dad's air compressor tank beforehand unless there's a filter inline to keep the air dry.
Replace the RD anytime the system is opened up. It absorbs moisture vapor. Vacuum the system in the hot sun for as long as possible. Any moisture vapor left in the system should boil off with a good vacuum pump. It must be clean and moisture free to work. |
#30
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I borrowed a flush gun from autozone that was a small pressure vessel that you put about an ounce of the oil cleaner in and you add compressed air. There are other methods that will work, anything that forces the flush oil into a high pressure mist will do the job.
Blow the components with COMPRESSED AIR (!) until it is no longer green. Like Whiskeydan said, clean everything. I would add that a nitrogen pressure test before a vacuum is beneficial, as it seats the seals and proves that the system can hold pressure. A vacuum does not do these two things.
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Mercury is a boxer 1984 300d 1999 Prelude Medici road bike Klein touring bike Klein mtn bike |
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