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Author Topic: Missing air tank - 4108a  (Read 395 times)
richard5933
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« on: November 02, 2017, 03:36:05 PM »

I'm working my way through getting familiar with my new 1974 4108a, and right now I'm stumped. I can't find one of the air tanks mentioned in the Operator's Manual (pg 58).

PRIMARY RESERVOIR
Primary reservoir is mounted horizontally on front axle rear bulkhead. Drain valve is located
just behind the left-front tire just above and on the same side if the bulkhead as the front axle splash
apron. Drain valve is closed with handle parallel to valve body and open when handle is at right angle to valve body.

The manual lists the Main Reservoir (wet & dry sides), Primary Reservoir, Secondary Reservoir, and the Parking Brake Reservoir. I have found all the tanks and drain valves except for the Primary.

Anyone have a clue what the manual is talking about and where this tank & drain valve are located? Maybe someone with one of the variants of this model will be able to confirm whether or not the manual is correct. I'm starting to wonder if a change was made in the design that is not reflected in this manual.
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Richard
1974 GMC P8M4108a-125 (Current Bus)
1964 GM PD4106-2412
Located in beautiful Wisconsin
KD9GRB
chessie4905
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« Reply #1 on: November 02, 2017, 04:14:35 PM »

My 4905 has: one under driver in compartment, two above batteries in compartment right behind passenger front wheel and one on bulkhead rear of rear axle mounted vertically with several of the brake system valves mounted next to it. It has a drain valve on bottom.
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GMC h8h 649#028 (4905)
Pennsylvania-central
richard5933
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« Reply #2 on: November 02, 2017, 04:33:01 PM »

My 4905 has: one under driver in compartment, two above batteries in compartment right behind passenger front wheel and one on bulkhead rear of rear axle mounted vertically with several of the brake system valves mounted next to it. It has a drain valve on bottom.

Thanks

Those all I have. Even was able to get them drained. There is the one additional tank listed in the manual that I can't find. Curious if your Operator's Manual also shows the tank on the front axle bulkhead? Maybe they changed things in production but kept using the same manual?
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Richard
1974 GMC P8M4108a-125 (Current Bus)
1964 GM PD4106-2412
Located in beautiful Wisconsin
KD9GRB
buswarrior
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'75 MC8 8V71 HT740




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« Reply #3 on: November 02, 2017, 04:42:05 PM »

Date of the manual pages?

The world changed a lot in 1975 for air systems...

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
chessie4905
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« Reply #4 on: November 02, 2017, 05:02:00 PM »

Unfortunately I'm in hospital right now with a knee replacement, so I can't check my manuals till I get out of here tomorrow or Saturday, but I'll check when I get home. Some of the change they did in those years were dual brake system and antilock systems. Also they had Special equipment options, referred to in manuals breifly and also in my wiring diagrams. They all had hub piloted wheel option. Believe it or not, you can convert if desired to the correct studs and wheels. The hub diameter is the same; convert the mms to inches, they're the same.
Coach net manuals list CDs for the early and late models produced, but have same part number. Also check out one that lists parts needed to convert to a V730, Sheppard power steering, in 4106's and 4104's, etc.
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GMC h8h 649#028 (4905)
Pennsylvania-central
richard5933
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« Reply #5 on: November 02, 2017, 05:10:25 PM »

Date of the manual pages?

The world changed a lot in 1975 for air systems...

happy coaching!
buswarrior

No idea. There is not a date on the Operator's Manual. It was not in the bus when I got it, so I ordered it online from Coachinfo.com

Perhaps my '74 model and the manual are not the same?
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Richard
1974 GMC P8M4108a-125 (Current Bus)
1964 GM PD4106-2412
Located in beautiful Wisconsin
KD9GRB
buswarrior
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'75 MC8 8V71 HT740




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« Reply #6 on: November 02, 2017, 06:09:49 PM »

A world of difference in the air system plumbing between a 1974 and a 1976, and a fine scalpel needs to be used in the transition over the top of 1975.

A few GM's also got optioned with DD3 brakes, just to screw things up further...

Got to have the right pages for the right bus.

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
Scott & Heather
Scott & Heather's buses: MCI-9 & MCI-102
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« Reply #7 on: November 02, 2017, 07:34:38 PM »

Richard, I wish I knew something about your bus but I don't. So I'm here just to say I'm impressed with how fast you're getting back into this after such a recent scare. You have my respect sir. Carry on. Hope to meet you someday.


Sent from my iPhone using Tapatalk Pro
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Scott & Heather
1984 MCI 9 6V92-turbo with 9 inch roof raise (SOLD)
1992 MCI 102C3 8v92-turbo with 8 inch roof raise CURRENT HOME
Click link for 900 photos of our 1st bus conversion:
https://goo.gl/photos/GVtNRniG2RBXPuXW9
richard5933
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« Reply #8 on: November 03, 2017, 02:02:38 AM »

Richard, I wish I knew something about your bus but I don't. So I'm here just to say I'm impressed with how fast you're getting back into this after such a recent scare. You have my respect sir. Carry on. Hope to meet you someday.


Sent from my iPhone using Tapatalk Pro
Thanks! If your travels ever bring you through SE Wisconsin, you've always got a place to park and plug in here.
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Richard
1974 GMC P8M4108a-125 (Current Bus)
1964 GM PD4106-2412
Located in beautiful Wisconsin
KD9GRB
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