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Author Topic: MC5 B - again...  (Read 6796 times)
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« Reply #60 on: April 03, 2011, 09:21:28 AM »

   Does anyone have a schematic of the air system? .

  Would anything electrical block air to the wipers, door lock, air gauge/buzzer? I'm sure I had full air pressure to the brakes, certainly much more than the 20 psi I saw on the gauge. The brakes were definetly releasing and applying (witnessed turning the front wheel) which IIRC takes over 60 psi to release? It takes over 60 psi to hold the emergency brake valve released, doesnt it?

    

  
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bevans6
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« Reply #61 on: April 03, 2011, 12:49:50 PM »

I don't have a schematic of the air system on a 5B.  It will be about the same as the MC-8 of the same year.  There were a lot of changes in the system detail in the 1970's, per Buswarrior, so look for a MC=8 manual of near vintage and it will be good for you bus for most things.

The gauge is supposed to read the accessory tank on that vintage of bus, which is the tank at the front beside the driver.  If you added air to the schrader valve in the same bay, it does not go to that accessory tank, it goes to the parking brake tank, which is why you were able to release the brakes.  From the parking brake tank, depending on specifics, it may or may not bleed out to the dry tank or  to the accessory tank.  If you want to fill the bus correctly without running the engine, add air to the ping tank at the back of the bus, passenger side, there should be a valve there too.  The low air warning runs off the accessory tank, so it will not shut off until the bus pressure is up properly.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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« Reply #62 on: April 03, 2011, 02:28:13 PM »



  The gauge is supposed to read the accessory tank on that vintage of bus, which is the tank at the front beside the driver. 

  If you want to fill the bus correctly without running the engine, add air to the ping tank at the back of the bus, passenger side, there should be a valve there too.  The low air warning runs off the accessory tank, so it will not shut off until the bus pressure is up properly.

Brian

  I figured out the front schrader only released the brakes, so I attached directly to the accesory tank and filled there. That raised the Bus suspension and brought air to various gizmos at the back, ie; when I flip those control valves I heard air come and go, etc..

  I found what I believe you guys call the ping tank, a small cylinder about 3 inches diameter by 6 to 8 inches long (IIRC), mounted vertically by the bulkhead where the compressor hoses junction. There was a schrader there, and there was air pressure there. I attempted trying to fill it off my compressor, but it wouldnt take any. Releasing the schrader it had good pressure there.

  Once the front tank was filled I closed the valve and shut down my compressor. The Bus did not have any major leaks, and held up the suspension all night and all the next day. There was still pressure for the brake system in the morning, but not enough to hold off the emergency brake valve.

   It has been my understanding as well, that the dash gauge and warning light should read pressure on that tank, but it is not doing so. Is there an electrovalve that would block air to that circuit that could be inop? There is also no air to the wipers or door latch.   
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lostagain
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« Reply #63 on: April 03, 2011, 04:30:48 PM »

Ignore me if you know already, but there is a little lever with a red handle under the dash to the right of the steering wheel that turns the door latch on and off. Up, toward you, the door latch claw will suck the door tight. Down will release it.

JC
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JC
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« Reply #64 on: April 03, 2011, 05:52:48 PM »

Ignore me if you know already, but there is a little lever with a red handle under the dash to the right of the steering wheel that turns the door latch on and off. Up, toward you, the door latch claw will suck the door tight. Down will release it.

JC

  I wont ignore anybody.

  I found that lever, says something like passenger door over ride? It doesnt do anything. I kinda had an idea that worked the lock. Any other ideas? I just assume that if there was a leak, id lose air brake pressure, and system pressure in general. Thats not the case, its only very slowly losing tank pressure overnight, its just not getting to the gauge, wipers, door lock....
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« Reply #65 on: April 03, 2011, 06:00:13 PM »

Paul, this just dawned on me: on my 5C, the ignition key has to be on for the door latch to operate. Worth a try on yours...

JC
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JC
Invermere, BC
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« Reply #66 on: April 03, 2011, 06:27:58 PM »

Paul, this just dawned on me: on my 5C, the ignition key has to be on for the door latch to operate. Worth a try on yours...

JC

  I didnt see a key switch anywhere. There is a master switch on the instrument panel between the start button and a hooded emergency stop. The rear panel back in the engine bay I had switched to front start. With the master in the up (on) position, I can start (attempt to start) the engine, and the blowers and lights etc., all operate. However, there are no emer flashers, turn signals, if there is another switch somewhere I havnt found it. 

  Where is your key switch located?
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lostagain
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« Reply #67 on: April 03, 2011, 07:43:18 PM »

I'm talking about the master switch on the dash. Has to be on for some things to work, like the door latch.

I don't know about your flashers and turn signals. Maybe look in the electrical panel outside below driver...

Sorry I'm not much help.

JC
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JC
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« Reply #68 on: April 03, 2011, 08:05:36 PM »

I'm talking about the master switch on the dash.

  Thats the one im talking about, right in front of you to the right of the wheel. In the up (on)position, everything is working except the things I noted.

 
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