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Author Topic: 1976 MCI-8 Will not air up on right side "HELP"  (Read 3859 times)
buylow
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« on: April 17, 2006, 02:12:40 PM »

Hi
My MCI won't air up on the right side but the left side airs up with no problem. I dont hear any leaks and the air gauge increases as normal and dumps when it reaches 100 something PSI. Where should I look for the blockage? Also, both front right and right rear dont air up.
Thanks Kurt
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tekebird
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« Reply #1 on: April 17, 2006, 02:24:49 PM »

Bad leveling valve.

BTW....your air sysstem should't dump at 100.....probably 120
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buylow
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« Reply #2 on: April 17, 2006, 02:30:21 PM »

It doesnt dump at 100psi it dumps at 100 something. I was not sure about the exact psi but 120 sounds about right.
Where would the leveling valve be located and what does it look like. can it be changed without crawling under the bus?
Thanks Kurt
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ChuckMC8
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« Reply #3 on: April 17, 2006, 03:03:21 PM »

Kurt, With air systems in paticular, in order to get help you need to list specific pressures.To troubleshoot air problems, it has to be first determined that your system is operating at correct pressures. If it isn't, it may as simple as changing the governor on the compressor, around $20 at NAPA stores. Just ask for a "D-2" air governor.
   The air leveling valves are just inside the drive wheel, on the bulkhead. I changed mine while I had the wheels off, although you can properly block up the bus and then silde under to tackle the job. Its a good opportunitty to adjust the slack adjusters on the brakes, while you're there.
    According to my Mohawk catalogue, the leveling  valves are $44.94 at www.mohawk.com 1-800-323-7652 My catalogue is a couple years old, so......
 There is one valve on each side in the rear, and one single valve on the center of the front axle.
The part numbers are 12C-6-1 Front and R.H. rear leveling valve.
12-C-6-2 is the L.H. Rear
 I consider the leveling valves and governor items that should be replaced when trying to bring maintenance up to date. I did on my coach.
     Kurt, I hope this helps, Chuck Lott Douglasville Ga 1977 MC8

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buylow
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« Reply #4 on: April 17, 2006, 03:20:42 PM »

Chuck
When you say "There is one valve on each side in the rear", is that one for the LR and one for the RR.  and "one single valve on the center of the front axle" do you mean one valve for both LF and RF? So there is only 3 leveling valves?
Kurt
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ChuckMC8
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« Reply #5 on: April 17, 2006, 03:25:04 PM »

Kurt, You are correct. It is a 3 point system. One in the front and 2 in the rear.  I can send you a picture of the parts diagram if you'll email me-just click on my profile-Chuck
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Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)
gumpy
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« Reply #6 on: April 17, 2006, 04:37:19 PM »

I'll go out on a limb here because I'm clairvoyant  Wink

The problem is a fairly large leak in your right rear air bag. Get out the soap, and if possible, hook the bus up to shop air. Spray the right rear bags well and you'll find the leak. Probably, if you use shop air, you'll find it simply by running your hand along the bags. It's probably going to be a crack in the bellow, just can't tell whether it's front or rear, or top or bottom roll.

Let me know how I did when you find it.   Cheesy

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Craig Shepard
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FloridaCliff
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« Reply #7 on: April 17, 2006, 05:33:32 PM »

Lots of good suggestions.

Kurt,

Did this just happen?  Or has the bus been sitting a long time?

Since most rear bags are fed from a common point this is isolated to the one side

Definately use the shop air to build up pressure.

You will be able to hear any leaks that would stop something from airing up.

If no leaks are audible is the rear leveling valve arm attached to the body/frame/etc?

Give us all some feedback and we will give you more options.

And block that bus up good. No one likes a squished Busnut!

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1975 GMC  P8M4905A-1160    North Central Florida

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DrDave
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« Reply #8 on: April 17, 2006, 07:03:24 PM »

The leveling valves are different on each side. There is a left side and a right side.
If you are going to do one, do both .. Been there...

Check to see if someone tripped the dump valve for the right side tag.. That will make it sag a little also.

If you are spraying bubbles stuff do the area above the drive axle along the frame, if you get bubbles there
then your airbox-beam is leaking

If your bus has had blocking plates installed along its lifetime, you could have one corroded out inside the
airbag rim. You wouldn't see it normally.

I dunno, Just some ideas.....
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NJT5047
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« Reply #9 on: April 17, 2006, 07:35:05 PM »

I'd put my money on the RH rear leveling valve.  Doubt the tags would cause what you're describing on an otherwise correctly functionng aired up coach...the tags only have about 2K lbs divided.   And an air leak that outruns a properly functioning leveling valve would likely be audible....if the engine isn't running.  Connect to house air for diagnostics.   
You may find that moving (driving a short distance) the coach will cause the leveling valve to start working again.  This wouldn't be a good idea if the drive axle airbag is totally flat and on the stops.  Even if it leveled, the RH rear leveing valve is still faulty and should be replaced.  Be sure the filters and check valves are in good working order.   Have you checked for a broken or loose leveling arm on the RH leveling valve?  May want to look at the simple things first. 
While your into the rear airbags and leveling valves, add some airlines and shunt them in the rear bay for your future leveling system.  Be a good time to consider this. 
Someone has already mentioned that an aired up bus is dangerous to work around.  If you have an inflated airbag and move the arm, or disconnect an airline, it's coming down.   Don't disconnect air lines when the bus is aired up. 
If you replace the air leveling valves, be sure you set the ride height before you get the wheels back on.   
As someone has already stated, the front is not part of your problem with lateral leveling.  That function is handled by the rear drive axle airbags. 
The tags have two valves inside the RH service door.  Check and mark the "inflated" and "deflated" position of the valves.  My MC9 was marked wrong.   You can reach behind the tags and check for an inflated tag airbag.   The tags only operate at prox 35lbs.   Should be a "low tag" air pressure light in the dash. 
Leveling valves are easy to replace and adjust.  Jacking the bus, blocking, and pulling the wheels are the hard part. 
Hope you have a solid surface to work on.   While your're under there, check your tanks for water, and bleed same off.  Should be dry. If not, think about servicing the dryer.   If tanks have oil in them, compressor is pumping oil.   
Good luck, JR     
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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TomNPat
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« Reply #10 on: April 17, 2006, 11:45:18 PM »

air it up until the maximum pressure is reached (about 120) and shut off the engine.  Run outside quickly and listen.  If you move as slow as me, have someone else shut it off!!!!

If it is a leak, you should hear it, if not I, like some above, would suspect the leveling bag.

TomNPat
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gumpy
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« Reply #11 on: May 15, 2006, 05:52:53 AM »

Did you ever find the problem?
« Last Edit: May 15, 2006, 07:18:36 AM by gumpy » Logged

Craig Shepard
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http://bus.gumpydog.com - "Some Assembly Required"
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