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Author Topic: MCI 8 air problem  (Read 2372 times)
thomasinnv
Derrick Thomas
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« Reply #15 on: February 17, 2012, 10:38:17 PM »

the only access to those front tanks is by crawling under the bus. be careful, busnuts have been squashed to death.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
buswarrior
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« Reply #16 on: February 18, 2012, 12:22:38 AM »

You don't need a shovel to find the rear electric junction box, just open the driver's side engine access door, the one on the side, not the rear. The junction box is mounted right there on the wall, to your left, inside the fender for the tag wheel.

If the temps are below freezing, you might want to just wait?

There are too many variables for trouble shooting for throwing frozen moisture in any random place into the mix.

I really, really hate wasting time working on something that doesn't need working on, due to bad diagnosis.

Some call me lazy, some call me smart...

happy coaching!
buswarrior

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Frozen North, Greater Toronto Area
bevans6
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« Reply #17 on: February 18, 2012, 04:00:43 AM »

There are four tanks on your bus.  The dry tank is behind the rear wall of the rear luggage bay on the driver's side, and the drain valve is through a small door at the foot of the wall just inside the luggage bay door.  The two tanks in the front axle bay are the emergency tank and the wet tank.  The wet tank is on the drivers side and the emergency tank is on the passenger side.  The pressure protection valve and the E-filter are mounted on the emergency tank.  There are normally pull type drain valves that you can attach a chain or cable to, or hook with a long stick with a bent end.  The last tank is the accessory tank, it's up front under the driver's seat in the compartment there.

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
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1978 Lola T440 Formula Ford
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buylow8
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« Reply #18 on: February 18, 2012, 01:11:17 PM »

Thomas or anyone else
Do you have the drawings for the airbags?
kurt
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buswarrior
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'75 MC8 8V71 HT740




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« Reply #19 on: February 18, 2012, 01:51:33 PM »

What drawings did you get from Thomas?

All that stuff you've mentioned in the thread is on the stock drawings.

Pretty rare for that E filter to get clogged.

Also, pressure protection valves tend to fail by letting the air through early, as the spring ages or breaks, not block it up completely.

As Brian suggests, is there air present in all the tanks, and drain them, and see what the recovery might be?

I'm thinking blockage, as opposed to failure.

happy coaching!
buswarrior

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Frozen North, Greater Toronto Area
buylow8
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« Reply #20 on: February 18, 2012, 02:08:24 PM »

Thomas gave me an air brake system drawing. i hope it warms up a bit more so my problem goes away on its own
kurt
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thomasinnv
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« Reply #21 on: February 18, 2012, 09:55:33 PM »

I just emailed you the suspension air schematics. I didn't even notice they weren't part of the schematics i sent you already.

BW, the pressure protection valve absolutely can fail in the described manner, and not just by opening too low. I had the same exact problem as the op describes a few months ago due to a sticky ppv. My air would go over 100 before the ppv opened. can be common in colder climates.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
buswarrior
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'75 MC8 8V71 HT740




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« Reply #22 on: February 19, 2012, 11:19:33 AM »

Crack open the lines leading to the ppv and give it a shot of your favorite air tool oil.

Be prepared to do a little re-adjust once it is freed up, but after it has been cycled a few times. let it settle in to its new found freedom.

My use of words may have led us astray?

Sticking is a blockage, which can be remedied,
failure requires the replacement of the component due to it being unable to perform as intended in a permanent manner.

Many apologies!

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
buylow8
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« Reply #23 on: February 22, 2012, 06:14:24 PM »

Thomas
thanks for the air suspention drawings.

I ran the bus again when the temp went into the high 50s and its still not working. I had a truck mechanic stop by and he hooked up his air compressor to the emerg fill air valve and was able to release the emerg brakes. i am going to drive it to his shop a mile down the road and have him fix it. i will post what the fix was
kurt
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buswarrior
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'75 MC8 8V71 HT740




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« Reply #24 on: February 22, 2012, 06:17:48 PM »

good news! you'd like for your mechanic to explain to you what he has done, what diagnosis he did, what he found right, and what he found wrong, and what he did to fix it.

Not so much for us, but for your own growing knowledge of how the beast functions.

If you learn as you go along, he gets more business, if you don't learn anything....

happy coaching!
buswarrior
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Frozen North, Greater Toronto Area
Scott Bennett
Scott & Heather MCI-9
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« Reply #25 on: February 22, 2012, 06:44:19 PM »

Kurt Just a side note on your engine stop lever. You said you have to manually kill it by pulling that lever. Is it stiff when you pull it? If so, it's merely not returning via spring to it's off position. You merely need to unseize the lever from it's likely seized washers down near its base. Fixed my problem. Much safer than reaching in there every time.
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Scott & Heather
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
˙ǝɯoɔlǝʍ suoıʇɐuop ˙snq ʍǝu ɐ pǝǝu ʎlqɐqoɹd ll,ǝʍ 'sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
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« Reply #26 on: February 22, 2012, 06:55:07 PM »

scott
the lever is not easy or hard to turn. it looks like there is an actuator that should push the lever but it looks like it or the lever was moved out of the way. i guess the guy before me had a problem with it and moved it. i never fixed it because it is about # 10,000 on my things to do list
kurt
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thomasinnv
Derrick Thomas
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« Reply #27 on: February 22, 2012, 07:27:25 PM »

the spring is not what activates/operates the engine stop lever, the air cylinder operates it. If it was moved to the side by the PO then chances are that once the air is up in the system you will find the air cylinder to be energized. you most likely have a faulty air valve, engine stop switch, or faulty wiring between the two. For those that don't know, MCI uses a remote air valve mounted on the rear bulkhead, which activates the air shutoff cylinder on the governor.
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There are three kinds of people in this world....those that make things happen, those that watch things happen, and those that just wonder what the heck is happening. Which one are you?

1977 MCI Crusader MC-8
8V71N/740
95% converted (they're never really done, are they?)
Scott Bennett
Scott & Heather MCI-9
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Scott & Heather


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« Reply #28 on: February 23, 2012, 04:56:06 PM »

scott
the lever is not easy or hard to turn. it looks like there is an actuator that should push the lever but it looks like it or the lever was moved out of the way. i guess the guy before me had a problem with it and moved it. i never fixed it because it is about # 10,000 on my things to do list
kurt

Oh ok...different problem than mine was.
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Scott & Heather
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
˙ǝɯoɔlǝʍ suoıʇɐuop ˙snq ʍǝu ɐ pǝǝu ʎlqɐqoɹd ll,ǝʍ 'sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
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