Re-sealing R4 compressor - PeachParts Mercedes-Benz Forum

funola · #1 09-20-2016, 11:23 AM

Just a week after filling the system with R12 R12 vent temp 85 300D 38.5F @ 87F ambient , 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 Vacuum flush AC system . 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.

leathermang · #2 09-20-2016, 11:31 AM

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....

funola · #3 09-20-2016, 11:37 AM

Quote:

Originally Posted by leathermang

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.

Demothen · #4 09-20-2016, 11:38 AM

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?

strelnik · #5 09-20-2016, 11:39 AM

Quote:

Originally Posted by funola

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.

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

funola · #6 09-20-2016, 11:48 AM

Quote:

Originally Posted by Demothen

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?

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.

Demothen · #7 09-20-2016, 11:50 AM

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!

funola · #8 09-20-2016, 11:58 AM

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.

funola · #9 09-20-2016, 12:02 PM

Quote:

Originally Posted by Demothen

...........
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.
........

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

Demothen · #10 09-20-2016, 12:08 PM

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.

leathermang · #11 09-20-2016, 12:22 PM

Quote:

Originally Posted by funola

...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.

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....

funola · #12 09-20-2016, 12:33 PM

Quote:

Originally Posted by leathermang

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.

funola · #13 09-20-2016, 12:41 PM

Quote:

Originally Posted by leathermang

So that tablespoon of oil was the amount left after evacuating the system .... sounds correct..
......

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.

leathermang · #14 09-20-2016, 12:48 PM

Quote:

Originally Posted by funola

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...

funola · #15 09-20-2016, 12:52 PM

Quote:

Originally Posted by Demothen

I............ Anyway, just trying to help. But feel free to keep nitpicking what I am doing. Have fun.

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.