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Author Topic: Putting new reed valves in my A/C compressor anything I should watch for?  (Read 4313 times)
RickB
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81 MCI 9 smooth side 8V71 Allison 754




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« on: July 22, 2010, 06:58:18 PM »

Hey all,

Before we left on our trip I had C&J take a look at why my bus A/C wasn't working and the diagnosis was it ate some reed valves Dan said they didn't do any damage so he thought it was safe to just put in some new reed valves. I have the oval head Carrier compressor and I don't know how many cylinders had the issue so I'm gonna take it apart tomorrow and put new ones in as needed. Any tricks to doing this? Lord knows there are tricks for installing most bearings and seals so I thought it would be wise to run it by everyone here in case someone has alot of experience with these monsters.would have had them do it but vacuuming out the system and refilling it is like 5 hrs of labor. The reed valves are $80 a head. I'll take some pics for future reference.

Dallas if you're lurking and reading this you better come back soon or a bunch of us will have to come looking for you. We'll be tracking in the kitchen and eating all your food and drinking,  well, we'll be drinking everything so it's your call.
You can come back soon because we need you or you can go broke when we all come down looking for you.

Rick

I
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gus
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« Reply #1 on: July 22, 2010, 08:56:30 PM »

This compressor is probably a different animal altogether, but I long ago gave up on repairing auto AC compressors because rebuilt ones turned out to be cheaper and more reliable in the long run.

After doing all that work to repair one it always happened that something else failed a few months afterward. Rebuilt one have a warranties, if they fail I just go get another one.

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PD4107-152
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Tom & Phyllis
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« Reply #2 on: July 23, 2010, 04:32:50 AM »

Rick,

Keep everything CLEAN!! Meaning like an operating room! The heads have to be torqued when installed. The oil has to be changed. If you still have refrigerant in the system, front seat the king valves to keep the system from moisture before you work on the compressor. If not, purge the system with nitrogen. Change the oil. Change the liquid line drier. Evacuate to at least 400 microns before recharging. Did I mention changing the oil? Roll the compressor by hand to see if everything works before you fire it up.

TOM
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'82 BlueBird WanderLodge PT40 being rebuilt
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TomC
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« Reply #3 on: July 23, 2010, 08:04:37 AM »

I believe the oval head compressor is a V-4.  Personally-I would exchange it for a rebuilt one.  It is almost as involved as rebuilding an engine.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
RickB
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« Reply #4 on: July 23, 2010, 03:32:38 PM »

Well, nothings ever easy is it?  Got the kits and got it all apart and ready to go back together and I thought I should spin the clutch by hand to get each piston to top dead center so I could make sure I had no shavings or gasket material and whaddya know.. one of the wrist pins has alot (I mean like a 1/4" alot!) of play in it. So, being quite sure that this would just fail miserably in short order I decided to pull the piston and replace either just the piston or the piston rod assembly and wouldn't you know it the rod is larger than the bore of the cylinder which means I have to pull the crank and then there's seals and the Lord knows what else so I'm debating bringing it in as is and seeing how much Steve at C&J would charge to just rebuild the lower end. I'll do it if it's unreasonable but if it's reasonable I'll probably have them do it. I want to find the guys who designed these buses and thank them for making them last and slap them silly for doing things like making the rod larger than the bore of the cylinder.

What the heck were they thinking? 

Well, I'll keep y'all updated...

Rick
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Busted Knuckle
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« Reply #5 on: July 23, 2010, 03:47:04 PM »

Quote from: RickB
I want to find the guys who designed these buses and thank them for making them last and slap them silly for doing things like making the rod larger than the bore of the cylinder.

What the heck were they thinking?

Well, I'll keep y'all updated...
Rick

I ain't gonna be the one who has to fix it in 5-25 yrs from now!
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RickB
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81 MCI 9 smooth side 8V71 Allison 754




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« Reply #6 on: July 23, 2010, 04:39:09 PM »

Those might be the truest words ever spoken Bryce Cheesy Cheesy ;Dce
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James77MCI8
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« Reply #7 on: July 24, 2010, 09:35:05 AM »

I'd put a want to buy on the boards. I have the old round head on my 8 that I am not going to use, But I don't think that is what you are looking for. The Compressor rebuild is not like rebuilding an engine. It is much worse.
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« Reply #8 on: July 24, 2010, 03:47:26 PM »

I learned all this with auto compressors, your experience will probably be much more memorable!!
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« Reply #9 on: July 24, 2010, 04:39:28 PM »

Rick,

Thanks, I peed a little.  I can identify with your experience.

 I don't know a darn thing about your compressor but I know one thing.....people are telling you to cut your losses and get a rebuilt item.  God only knows what that would cost.  I have an alternative for you:  The bus unit is WAY over built for our use. We never have the heat load of fifty people and we don't need to get the temp down in 3 or 4 minutes.  Save money and FUEL and install a healthy auto compressor.  I think they can be had in 4 ton and that should be enuf. Make sure you pick one that is cheap and plentiful in the wrecking yards.  Don't go with the "old GM style" as they are no longer supported but they were darn good.  The Jap brands are way more efficient.  They have a "scroll" compressor that is super efficient but I don't even know what that is and I hear they are spendy.

Good luck,
John
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RickB
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« Reply #10 on: July 25, 2010, 02:29:58 PM »

John,
If you change the compressor I believe you would have to downsize the entire system. I'm fairly certain that all the components are relatively sized. These compressors are indeed complex but they aren't rocket science and they are no where near a complete out of frame on one of our bus engines. I would compare them to a mid 90's era snowmobile engine. They're much cleaner internally because they aren't burning carbon though. If I have Steve rebuild it would be because I don't have time more than because I feel incapable. Other than the crank seal and keeping track of the piston/cylinder correlation, removing the crank doesn't seem super difficult. I'll keep you all informed.
Rick
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JohnEd
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« Reply #11 on: July 25, 2010, 06:35:19 PM »

Rick,

Competence never crossed my mind.....yours or any ones.  Given mine I sorta stay humble.

Nick has said in the past that you have to match components.  I don't get that and I wish he had provided more info or a steer to the source.  Maybe he was being kind to me.  

The advice from day one when I first fell off that turnip truck was to rip out the OTR bus AC.  It was said to be really expensive to repair, was way way over sized for a conversion, and was eating a MPG to keep it running.


I don't know a darn thing about your compressor

I still feel that way.

You gotta know that I wish you the best.  Would be nice if you could document your rebuild and provide insightful comment.  But then it would be nice if I did that too and so far I haven't. No bus work so far.

Please do keep us informed.

Thank you,

John
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RickB
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« Reply #12 on: July 25, 2010, 08:20:40 PM »

John,

The reply regarding the auto AC compressor was the only one which was responding to you. There were earlier posts that compared rebuilding our bus engines to rebuilding one of these compressors and I respectfully think thats an apples to oranges comparison. An out of frame for an 8V92 is between 12-17k and a rebuilt oval head compressor is between $1100 and $1500. In all honesty I was surprised at the simplicity of the top end of the motor. I am normally a hire it out if it's too tough kind of guy but putting in new reed valve kits (they are pre assembled) is a relatively simple job. I would compare doing one of the three heads with changing an air filter. It is nowhere near as hard as rebuilding the cooling system! Now that was a serious undertaking that required a wide variety of skills from rubber and metal fabrication to installing new speedy sleeves and seals in the blower box. Not to mention pulling the old radiators and installing the new ones. Those radiators and the blower box with the scrolls are heavy and awkward. Getting the AC compressor out was a breeze compared to that. I am hoping that Steve will do the bottom end for a reasonable fee as I am getting a bit weary of "always" working on the old girl and he can probably do this in under an hour although I bet the flat rate will call for 2-4 just for the bottom end. I'll keep you all informed and I hope to have bus air again by next weekend.

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« Reply #13 on: July 26, 2010, 08:12:33 PM »

The 4905a I bought a while back has two of the old GM style compressors in parallel. Both are mounted on a fabricated bracket driven from a common pto drive pulley.  It was converted to 134A at the same time and used as a seated church bus for several years with that configuration. Of course the freon had leaked out by the time I got it so I dont know how well it worked but I assume it was passable.

-Tom P.
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Tom Phillips
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« Reply #14 on: July 27, 2010, 03:45:39 AM »

I just had my OTR air system rebuilt. New compressor, system flushed, other parts replaced, recharged etc, etc. Finalk cost $4300.00 by a local Carrier service center. Now I have cold air while traveling and don't have to run 2 roof tops and the generator. I can use them as a backup if the OTR fails. Just my feelings on it and the way I prefer.
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Steve Canzellarini
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1989 Prevost XL
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