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Shaft seal replacement troubles

rweston on Wed August 19, 2009 12:18 PM User is offline

Year: 90
Make: chev
Model: sub
Engine Size: 5.7
Refrigerant Type: retrofit
Ambient Temp: 90
Pressure Low: 0
Pressure High: 0
Country of Origin: United States

R4 compressor./ retrofit
I recently had a serpentine belt partially break. Only the inside grove on the belt broke. All the others sections stayed intact. This made a whip out of the broken section which in turn cut everything in its path except the ac hoses. The power steering hoses, radiator hoses and the radiator have all been replaces and the only thing left was the coil on the ac clutch. (it also cut the electrical connector off).
Upon removing the clutch and coil I noticed that the shaft seal was leaking slightly. It seemed to be a good time to replace it also.
After ordering your seal kit I replacing it along with the new o ring and new retaining clip. Lubricating all before installation. Using great care great care and plenty of time and patience in getting the new seal on without damaging it over the threads on the shaft end and the increase of the shaft diameter right after the threads. (I don't know how you could get past these obstacles without the tool that covers them for installation purposes.)
Now everything is back together and I tried to pull a vacuum last night. I could only get it to down to 20. when the vacuum was shut off, it only took a few minuets to drop back to 0.
All the work was completed with the compressor on the vehicle and a lot of the front of the truck removed. I had more than enough room to work and even see directly into the the front of the compressor. Every thing looked good as I reinstalled and examined it, but it doesn't hold a vacuum in fact it must leak quit a bit to drop so readily back to 0.
Just one note. the old seal that was remove had quit a large split in it but even at that, the leak was small. One small pinhead size bubble every minute.(way too much to live with)! When I removed the refrigerant, it still had almost 2.5 lbs of the 3.5 lbs in a full system.
Her's my questions. The shaft seal is tapered around the shaft pointing inward. I can understand how pressure from the inside trying to get out would force the seal tight around the shaft creating a good seal. But what happens when the vacuum is on the inside and now the pressures are trying to get in the seal from the outside. What is there to hold them out? Does the new seal need to be seated some how before it makes a good seal around the shaft?
I'm about ready to remove the compress to the bench and start over, but I wanted some knowledgeable opinions before I start again.
I'm afraid I have pulled so much air into the system that it might be a good idea to replace the pag oil now.
Thanks for looking at this.
Rex

GM Tech on Wed August 19, 2009 12:36 PM User is offline

Did you replace the o-ring in the front head att the same time? did you clean the shaft seal surface on the shaft? did you somehow stretch the shaft seal too big?-- do you have the correct seal?- there are two out there- the other one is for a bigger shaft- so this alone could be your problem-- see this thread

Shaft seal discussions- size and methods

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

rweston on Wed August 19, 2009 2:25 PM User is offline

The seal kit ordered is 21-32504-g. It has three items; an O ring, a seal, and a clip. This is exactly the items that came off the compressor. I compared the items before installing them. the O ring looked identical and so did the clip, but the seal had not been stretch out yet so the inside was still much smaller, other than that, they looked the same. The measurements on the old seal are .845 in (21.46 mm) from metal to metal (inside metal lip) on the inside of the seal looking out. The old expanded seal itself measures .540 in (13.72 mm). and the outer edge of the seal measures 1.240 in (31.5 mm). The o ring that goes around it is just slightly smaller. I haven't removed the compressor yet so I can't measure the shaft size. I don't know the part numbers of the individual parts since it came as a kit.
I had read over the link for the seal replacements before I ordered the kit, It was very helpful. I believe I have the correct of the two seals.(the smaller). When searching on the website for seals, I didn't find a match so ACKITS helped me look it up.
The shaft wasn't very dirty and still quit shiny, so was the inside of the of the tube the o ring fit in. They were both cleaned well and lubricated before replacement.
I used a tool to slide the new seal on to the shaft. It covered up the threads and expanded the seal to be the same diameter as the shaft. Great care was use since it had to stretch the seal a lot to fit on to the shaft and I didn't want to split it as the old one had been split. I don't think it was over stretched.
Any suggestions?

Also is the seal tight enough to overcome the pressures of a vacuum right from the initial installation? or do they need to first be pressurized to get a good seat on them? If by chance it was over stretched, will the pressure from a charged system force the seal lips onto the shaft creating a good seal?
thanks again Rex

GM Tech on Wed August 19, 2009 2:34 PM User is offline

Millions of teflon seals were installed without problems- in the same manner you describe- no pressure to seat, a vacuum is the first thing they see- so that is not the issue- put a balloon over the snout (remove pulley works best) if in doubt- a vacuum will suck the balloon in- or pressure will blow it up-

Of course the seal goes in with the tool holder ring on top-as you have to have done......I hope

also you did oil the seal surfaces as you installed- I hope...

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Wed August 19, 2009 at 2:35 PM by GM Tech

rweston on Thu August 27, 2009 10:58 PM User is offline

Time to get back to the leaky seal problem. I tried the balloon trick today and filled the system with nitrogen. sure enough, the seal was leaking again. I thought it might have been the o ring around the seal but no such luck. I have taken the compressor to the bench this time. I'll see if I can't do a better job on the bench replacing it again.
Would using Nylog do a better job to help it on the shaft than just using pag oil ? I don't have another new clip ring but do have the original and the just replaced one that came in the kit. both look good. Do you see any problem with reusing the new one again?
Thanks again for your help.
Rex

rweston on Fri August 28, 2009 12:36 PM User is offline

After removing the seal, I find that the seal was nicked by the key way slot as the seal was pushed down the shaft past the termination of the key way slot. any sugestions on avoiding this next time?

GM Tech on Fri August 28, 2009 1:11 PM User is offline

Yeah- use the dog-pecker erhhhhh-- I mean shaft seal protector tool......or use heat shrink wrap or anything else over the keyway...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Chick on Fri August 28, 2009 9:58 PM User is offlineView users profile

As gm tech stated, "oil" the shaft good and use the shaft seal protector.. Nylog, although I use it on everything is just to thick for shaft seals, use mineral oil, or ester, but make sure you lube it good and protect the seal from the key slot.. Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

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