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Author Topic: Air compressor woes  (Read 1463 times)
FolkBus
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1967 MC-5A - 1949 Crown Supercoach




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« on: December 11, 2013, 04:01:05 PM »

Hi all

I've got a MC-5a with a 8v-71 and as most of you know getting to the compressor sucks ( I put that nicely).  I think the diaphragm for the unloader, read governor, is cracked. It will only air up to around 30-35lbs os so.  When I shut it off I can hear air leaking from the compressor area. This started being a problem on my southwest trip two days before getting home (thankfully it waited to completely break until I got home).  When I started the bus it would only build to the stated pressure. If I shut it off and let it leak off then restarted the bus it would build up normally and off we went towards home.  On the last day before getting home I had to repeat this cycle 3-4 times before it started to behave.

All of this is leading to the question of is the unloader accessible and part of the compressor head?  If so, I can actually get to that part of the compressor with minimal (tongue in cheek) grief.

Thanks

--Mike

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Mike and Debbie McNeil  Ridgway - Montrose, CO
1949 Crown SuperCoach (Amazing Grace) Conversion 1972  Pancake 220 Cummins  Fuller 5 Speed

1967 MC-5A  (Serenity)  Conversion 1986  8v-71N   Allison MT-644
Ralph7
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« Reply #1 on: December 11, 2013, 04:12:30 PM »

the  MC-5 I worked on had an access hole in the floor directly  above the compressor and easy to get to.  hope no body covered the access !!!!
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gumpy
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« Reply #2 on: December 11, 2013, 06:06:13 PM »

Stuck valve in the governor. Replace the governor or rebuild it.
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Craig Shepard
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bevans6
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1980 MCI MC-5C




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« Reply #3 on: December 11, 2013, 06:11:35 PM »

The governor is very easy to change in the MC-5.  The compressor itself not so much, but the governor is very accessible through the floor hatch. Undo two hoses, take out two bolts and it's off. 


Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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luvrbus
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« Reply #4 on: December 11, 2013, 06:19:52 PM »

If he has a air dryer and it needs servicing he will have those symptoms also
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« Reply #5 on: December 12, 2013, 04:24:58 AM »

I had the same or very close to the same symptoms about 8 years ago. Got a new governor for $20 and it solved it.  Smiley
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
Mex-Busnut
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« Reply #6 on: December 12, 2013, 04:51:55 AM »

Ahh... I wonder how many blocked the floor access hatches in their buses (not only this model) when they did their conversions?
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
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Ed Hackenbruch
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« Reply #7 on: December 12, 2013, 05:07:23 AM »

Luckily the PO didn't block mine when he did the conversion. Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
FolkBus
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« Reply #8 on: December 12, 2013, 05:48:06 AM »

Thanks all,

I'll be checking and hoping that the PO didn't block the access hatch.

--Mike
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Mike and Debbie McNeil  Ridgway - Montrose, CO
1949 Crown SuperCoach (Amazing Grace) Conversion 1972  Pancake 220 Cummins  Fuller 5 Speed

1967 MC-5A  (Serenity)  Conversion 1986  8v-71N   Allison MT-644
bevans6
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« Reply #9 on: December 12, 2013, 09:46:07 AM »

It's kind of funny - my bus had a queen bed with terrible access to the hatches when I got it.  I converted to twin beds because I kept hurting myself trying to walk around and over the wheel arches and such - just not enough room.  I thought "well, I'll have access now if I ever need it..."  A year later, when I was changing the engine, boy did I need that access!

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
B_K
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« Reply #10 on: December 12, 2013, 10:52:46 AM »

Ahh... I wonder how many blocked the floor access hatches in their buses (not only this model) when they did their conversions?

Ya know thatz funny you mention that.

I remember when Cody was at our place once and had a cracked exhaust manifold.
He asked "So how hard is that going to be to fix?"
I told him ah it won't be to bad with getting in here on the drivers side and down through the access panels in the floor.
All the sudden he had this deer in the headlights look and asked "What access panels in the floor?"
I told him oh in the bedroom there should be removable panels for a mechanic to access the engine/trans for service.
He got this even more horrified look and said "This bus has no panels like that! I built this thing and I can assure you it's got 2" of solid floor from front to back"
I asked are you sure?
He told me "Yes I'm sure. I bought this bus with NO FLOOR AT ALL and I didn't know anything about access panels!"

I just looked at him and sighed and told him Well looks like it's time for that rear bedroom remodel Libby & you wanted.

He responded "But we never wanted to remodel the rear bedroom!

I just looked at him and laughed and said  well ya do now!

He was horrified, mortified and pissed all at the same time.

But he took power screwdrivers, prybars, wrecking bars and a sawzall in the bus and a few hrs later he came out and said "We now have access!, Just becarefull not to fall thru!

I went in and rolled out laughing because he had cleared about a 6'X6' hole with plenty of room to just slide down in beside or on top of the engine/trans and do anything ya wanted to!

But on the bright side Booger and "The Don" had plenty of room to get in there an get'r done!
Grin  BK  Grin
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Dave5Cs
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1979 MCI MC5Cs 6V-71 HT-740 Allison, Roseville, CA




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« Reply #11 on: December 12, 2013, 05:09:39 PM »

Has anyone ever opened up a large hole other than Cody's way LOL, under the bed and cut out all the metal etc with big doors to get to the motor trans etc? I always wanted to open mine up in My 5C.

Dave5Cs
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B_K
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« Reply #12 on: December 12, 2013, 08:51:39 PM »

Cody was very careful not to cut out the metal cross members (he nicked a few) but he gave us plenty of "breathing room"

I do not know what he ended up with when he reassembled it. But best as I remember he more or less covered it back up and put the bed back down until he got home to "fix it right" (don't quote me on that as I wasn't involved after the manifold was replaced)
Grin  BK  Grin
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Brian Diehl
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« Reply #13 on: December 13, 2013, 07:32:24 AM »

I ran into a similar problem after camping for the weekend.  I went to start the bus and it would not air up.  I purged all the air from the system and then restarted.  The air pressure built as normal.  Before driving I did a bleed down test and sure enough, the air pressure would not build up again.  Knowing this had to be a problem with the governor and having all my tools with me as I usually do I set about taking apart the governor.  The governor is easy to get to on my engine.  I opened it up and found the piston had created wear marks on the side walls of the governor body and was holding up the piston due to the extra resistance of the "lip" worn in the body side.  To solve this I found I could rotate the piston about 90 degrees and it would no longer get hung up on the lip.  I put the governor all back together.  Air down and air back up tests were performed to be conclusive that I had a working air system again.  I then drove home with an extra careful eye on the air pressure just in case the valve should hang up again.  Once home I quickly replaced the governor with a new unit.  Simple and easy on the road fix.  Never leave home without your tools!

Here is an exploded view of the governor showing the piston and valve body: http://www.manualslib.com/manual/392610/Bendix-D-2-Governor.html#manual
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FolkBus
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« Reply #14 on: December 16, 2013, 05:11:15 PM »

Hi all

Thanks for the advice. The PO did not seal up the access hatch for the compressor.  Replaced the governor ($18.00 at Colton Truck Supply Montrose, CO) and all is working fine.

Thanks again

--Mike
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Mike and Debbie McNeil  Ridgway - Montrose, CO
1949 Crown SuperCoach (Amazing Grace) Conversion 1972  Pancake 220 Cummins  Fuller 5 Speed

1967 MC-5A  (Serenity)  Conversion 1986  8v-71N   Allison MT-644
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