Re-sealing R4 compressor
 

Just a week after filling the system with R12 http://www.peachparts.com/shopforum/diesel-discussion/380380-r12-vent-temp-85-300d-38-5f-%40-87f-ambient.html , I noticed a spot of oil on the driveway, right under the R4 compressor. Crawled under and saw bubbling green dye oil on the bottom lip of the R4 rear casing. I thought about resealing the R4 at first but since it pressure tested with no leaks (over time and under water), I took a chance and just used the old R4 as is. Well I lost 2.9 lbs of R12 due to old o-rings in the R4 and had to buy more parts and do more work.... R4 seal kit, receiver dryer (cut open to see how much oil was in it- there was none!), flush chemical (2 gallons of Kleen Strip denatured alcohol), PAO-68 oil.

The R4 reseal job (every o-ring as well as the shaft seal) went well with the tools I made and some rental tools from Autozone like the clutch puller. I did not get any pics of the clutch or the front shaft seal... too busy and forgot. There are a few good youtube videos (search R4 compressor reseal) for reference if you are interested in doing this job.

The AC is back up and running again although for the interim I put in R152a as a temporary refrigerant. I will run that for a few more weeks and if nothing else goes wrong, I will put in R12. I do not expect anything else to go wrong but you never know!

I also got the opportunity to try out a new flush method using vacuum http://www.peachparts.com/shopforum/diesel-discussion/380881-vacuum-flush-ac-system.html . It is amazing how easy and neat a system of flushing that I have just cobbled up. Nothing has to be removed other than the receiver dryer, TXV and the R4, which are components that should not be flushed anyway. I will start a new thread on it later.

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I am really sorry you lost that R12... and have had these problems...

As to the ' no oil ' in the receiver dryer.... when the AC is working that receiver dryer has liquid refrigerant in it... mixed with oil.... and the refrigerant is forced to go through the area where the dessicant is...

EDIT... really nice pictures....

I don't feel sorry at all since It was a great learning experience and I do have cold AC. If after all the work I've done and the AC is still not working, I'd be really pissed and probably push the car over the f****n cliff!

The first receiver dryer that ran for many years that I cut open had about a tablespoon of oil in it. The second one which ran for a week had no oil in it.

Did you have to bend the tab on the outer casing to remove it? Is there any way you can add an extra reinforcement to prevent the casing from pushing forward like mine did?

Please do not push the car over the cliff, I'll take it off your hands.

The tab must be bent out to remove the case. I don't think adding extra reinforcement is of any value. In your case, IMO, with the over pressure, the blow off valve should have released if the R4 was correctly installed and nothing was wrong with it.

I really don't see how I would have had an overpressure without even having the full amount of r134a in the system. Just remember that bending that steel will have fatigued it slightly.
Edit: Right right, my memory is horrible. I was experiencing higher than expected pressures when it failed, though not by much. Never did figure out why that happened.
Anywho, good luck!

Did your tab get bent with the catastrophic failure? Mine didn't, the case did not move at all. it was a very slow leak in the very bottom of the case. I think my leak was due to corrosion of the steel casing and the shrunken 30 year old o-ring.

How can you say "though not by much" when you did not have any gauges on it?

I had gauges on it during the fill. I dont have a perfect memory, obviously, but we went maybe 10psi over the recommended pressure for temp that day. It was a cool day, the pressure at say 100 ambient is still much higher than what I ever reached. Unless something else went crazy in the day between filling it and it failing.
And yes, my tab bent when it failed. I was trying to suggest adding an extra bracket since bending your tab during the rebuild process would have fatigued the metal slightly. Anyway, just trying to help. But feel free to keep nitpicking what I am doing. Have fun.

So that tablespoon of oil was the amount left after evacuating the system .... sounds correct..
Perhaps the fact the second one had NONE is part of the reason it only ran a week..... looks like no oil was being carried around the system by the refrigerant to keep the compressor lubed....

The oil was filled with a syringe 4 oz in the compressor and 4 oz in the receiver dryer before charging. There was plenty of oil in the compressor when I removed it before flushing. I cut open the receiver dryer just to see how the oil is distributed in the system after running. To my surprise, there was none in the receiver dryer that ran for a week. The oil is in the rest of the system though since the flush that came out was green and the suction hose at the manifold was dripping out oil.

In my experience, evacuation does not remove any oil from the system. Refrigeration oil is thick, you cannot blow it out with compressed air either since it whips the oil up into an emulsion/ cream and makes it thicker and more difficult to get out. The only way to get all the oil out is to thin it with a solvent then blow out the oil/solvent mixture with compressed air. And you may have to do that more than once depending on method used.

I totally agree.... and that is also the reason we say that the receiver dryer can not be dried by placing the system on a vacuum.....

''To my surprise, there was none in the receiver dryer that ran for a week.''Funola

Surprises me also... how it can be circulating properly and NONE be left in the receiver dryer ? That is rhetorical... I do not expect you to know the answer...

I am sorry you feel that way. I ask all these questions so I can gain knowlede, not to nit pick. I learn a lot by just reading problems that members post here. I learn even more if I ask questions and sometimes I even help them solve their problems.

I do not have a pic of the bottom of this one week old dryer but it was totally dry (on the bottom). The filter material also felt totally dry. Some of the beads (the dark ones) I assume has absorbed some oil, the light color ones has not absorbed any oil.

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Funola, I am glad you are cutting these things up and posting good pictures of them...

There are 2 large o-rings sealing the R4's steel casing. Both o-rings are the same but the steel case is bigger in diameter on the manifold end than the clutch end (I assume to make it easier to install), which makes the o-ring on the manifold end seal less tight. There is a bracket on the manifold (the one with a long thru bolt) that prevents the casing from sliding towards the rear (firewall). Because of these 2 factors, the rear o-ring is more likely to be blown out, and the casing can only slide towards the clutch. I do not know what the blow out relief valve is set at but I'd assume it should blow before the o-ring blows.

Do you have a picture of the relief valve?

4th pic down, the brass one is the removed relief valve. 3rd pic down is the removed aluminum plug for the switch port. Mine has no switch. To the right of the green o-ring in 3rd pic down is the same pressure relief valve.

Thanks. I wish i had some better pictures of the one that failed. I dont recall seeing that valve. I will check the one that was in the car when I bought it. Maybe certain brands of new compressors don't include them?
I think that the pressure switch at the drier is also supposed to cut out the compressor at high pressures, I don't have the part in front of me right now to check what Psi that should happen.

Also, I posted those pictures of the evap housing you asked for to my main rebuild thread in my signature.

Domothen, I am just going from memory ... but I think that is only a LOW cutout sensor on the drier....in case the system has a leak...... I know that when my 95 lincoln radiator fans went out my AC blew the not replaceable blow off valve ... but it was separate item than the low pressure switch... and not on the compressor....

After r&r the compressor twice, I can do one in less than 1/2 hour now. Here are some tips:

1. Do not follow the FSM's recommendation to remove the compressor with manifold attached! It makes the job much harder and you'll be cursing a lot! Remove the 15 mm wrench manifold bolt and the 13 mm wrench through bolt and let the manifold hang.

2. Slacken belt tensioner all the way.

3. Take pics or note where the thick spacers go (3 of them) before undoing the 3 long compressor 19 mm wrench mounting bolts. Keep the compressor in the same orientation as mounted and it will come out without spilling any oil.

On installing the R4, do not tension the belt before threading the suction hose fitting onto the manifold fitting (that's where I filled the compressor with oil). I spent 45 minutes trying and could not get it started because it was cocked and I feared cross threading it. I finally gave up and loosened the belt tensioner and lowered the compressor so the fittings would align and the fittings thread together easily first try. My belt was at the end of it's adjustment and that may have aggravated the situation.

I'll try to remember to grab a picture of the one I have tonight. It's not the original switch anymore, it's the updated version with high/low pressure sensing. The part listing doesn't specify, but I think it had small writing on it indicating the pressure range it allows.

I think the pressure switch on the receiver dryer on our W123's is called a binary switch, meaning it cuts in or out at 2 different pressures. The low cut in is around 29 psi from memory (I tested mine). I was unable to test it at high cutout because the digital pressure gauge on the test set I built only goes up to 150 psi and I did not want to risk over pressuring it.

I think that in case of a black death... at the very least.. the FSM says to REPLACE that manifold... as it is not able to be cleaned..... we had a thread on this lately....
this info is just for people with a parts car available or salvage yard.. .. since buying a new manifold is not possible as far as I know.

I do not believe the FSM in this instance. The W123 manifold has 1/2" i.d and 5/8" id passages and can be easily flushed of black death and metal particles. The parts that are more difficult if not impossible to flush that has suffered black death will be the evaporator and condenser, depending on the size of the particles. Demothen posted sizes of the evapoartor tubing, some of them are necked down in size.

I thought it amounted to a tight turn...made necessary by the tightness of the engine compartment stuff.... and a pocket which might not be flushable.. we discussed this in another thread...

The manifold is attached to the compressor in this pic. Do you see any tight turns?


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Was that recent thread... on a different model MB ?

My guess as to why the FSM calls for replacing the r12 manifold on the W123 instead of flushing it would be that you'd need to fabricate an adapter plate with a loop and gaskets to use a pressurized flush on it. Of course that was written for 1970's and 1980's parts pricing and availability. When restoring cars sometimes you simply can't follow the FSM due to parts availability, pricing, and equipment availability.

If you're using a liquid flush and blowing it out with compressed air, I cant imagine any reason why you couldn't flush the manifold either on or off the car. I flushed mine that way off the car.

Is thread you guys are thinking of might have been one for a later model car with an "accumulator canister" as part of one of the hard lines?

Yes, sure could be....

Great job! Thanks for posting this thread!

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Forgot I took a video https://www.youtube.com/watch?v=lOMwCVUurUw of the R4 oring leak. At around 7 pm, I put a catch can under it when I noticed the drip on the driveway. You can see the green dye oil slowly bubbling. Engine was off and the static pressure from the R12 refrigerant was somewhere around 70 to 80 psi. Immediately after this video I started the engine and ran the AC, compressor did kick on but vent temp reached was only 60F at around 80F ambient. The last time I drove it a day or 2 before, it was ice cold.

The next morning the bubbling stopped and the compressor no longer kicked on.

Good news is the AC is working fine so far after the compressor re-seal flush, evac and fill with refrigerant . We'll see if it continues to work fine or if something else fails. The system has the old compressor, hoses, evaporator, condenser. Only thing new are all o-rings and seals, TXV and receiver dryer.