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Author Topic: Mci 9 air question  (Read 1729 times)
jatnip
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« on: December 26, 2006, 08:53:39 PM »

I have an 1979 MCI 9.  Question.  If I air up the bus with shop air at right side engine compartment door at the air line there that has a valve on the air line, will it air up the entire system or is there a check valve somwhere and only air up part of the system?  I was thinking that if I ran into an aircompressor problem while traveling could you hook up an 115 volt air compresser to this line to get home?
Jim
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rayshound
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« Reply #1 on: December 26, 2006, 09:16:14 PM »

The valve in the right side engine door mounted on the fiberglass fender well  is a drain for the ping tank comming right off the aircompressor discharge. When I purchased my mci8 it already had a air chuck disconnect screwed into the valve. I hooked my shop compressor to it and pumped up everything without a problem. It also goes through the dryer to keep it dry.  Ray
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rayshound
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« Reply #2 on: December 26, 2006, 09:21:02 PM »

After rereading your post I'm not sure if you could use it to drive home on. I understand that the engine compressor is some where around 13 or 14 SCFM. Thats a large amount of air flow. That would take a nice sized shop compressor. I'm sure all of the 14 scfm is not used but the air brakes would use a good bit and if the compressor cannot keep up the brakes would start to apply due to low air pressure.  Ray
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TomC
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« Reply #3 on: December 26, 2006, 11:13:16 PM »

In 25 years of truck driving 1.3 million miles with my own trucks, and now with my bus, I have NEVER been stranded with a faulty air compressor.  If you have a question about the air compressor on your bus-have it rebuilt with a new governor-they are increadably reliable and should last many thousands of miles.  That will cost a whole bunch less than trying to set up an electric air compressor for emergency stand by.  Course it would be nice to have an electric air compressor for other uses and for initial airing up of the bus at the campground.  I am currently looking for about a 1hp that is a quiet running compressor.  So far, not too much luck.  Good Luck, TomC
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DrivingMissLazy
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« Reply #4 on: December 27, 2006, 04:57:54 AM »

After rereading your post I'm not sure if you could use it to drive home on. I understand that the engine compressor is some where around 13 or 14 SCFM. Thats a large amount of air flow. That would take a nice sized shop compressor. I'm sure all of the 14 scfm is not used but the air brakes would use a good bit and if the compressor cannot keep up the brakes would start to apply due to low air pressure.  Ray
The air compressor is not required to keep up with instant air usage. That is the purpose of the air storage tanks. If you are coming down a mountain and using the brakes excessively by on and off operation, then even the main compressor would not keep up.
By judicious use of the brakes, very little air is required while driving normal and a shop compressor would get you home with no problem. The same way that a shop battery charger can get you home if your main alternator fails. Just make sure your genset is working good.
BTW, it sure is nice to hava an auxiliary air compressor installed so that you can air up in a campground without disturbing your sleeping neighbors. .
Richard
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« Reply #5 on: December 27, 2006, 07:38:12 PM »

Its true it doesn't take much air for occaisional brake applications. I've got a pancake compressor in one bay with an air line run back to the air chuck by the dryer. Don't ever leave the air line hooked up except for initial air up or emergency. Also, it is very nice in the campground because you can air up the system and move the rig without smoking out the neighbors. Also works nice for bike tires, toad tires, etc.
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Fred Thomson
John E. Smith
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« Reply #6 on: December 29, 2006, 08:01:59 PM »

I was thinking that if I ran into an aircompressor problem while traveling could you hook up an 115 volt air compresser to this line to get home?
Jim
Jim, in a word... No.  We use shop air here to air up MCI's, and it takes sometime up to 20 minutes to get up to 120 psi.  MC-9's have such a large air capacity -- four large air tanks, ten air bags plus all of the associated plumbing.

If you are planning on taking a large compressor though, there is a way that it could be done.  Get a 1/2-inch or 3/4-inch quick disconnect and plumb it into the supply line at the compressor.  When needed, just hook up your emergency compressor to it -- it will still take several minutes to build air, but a large enough compressor should provide enough to let you roll.

Another option is to just carry a spare good compressor and change it out when needed.
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John E. Smith
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« Reply #7 on: December 29, 2006, 08:31:40 PM »

After my experience last week with my Eagle I will share what I know.

Knowing the air demand for my Eagle is differant than your MCI I can only speak for my experience.

I will never go without auxillary air. I realize the compressor that runs off the motor should last quite awhile, but, you never know. I was fortunate to locate a compressor when mine went out. I had several people check all over Fontana for a mate to mine, no luck. I hooked up mine just to move the coach off the exit on I-10. Then I tackled trying to find one. It only took ten or fifteen minutues to air it up to move it. Two days to find one.

Have a good one on your coach then have a rebuilt unit on standby with a new govenor on it. They don't take up much room.

You never can have too much air.

Happy Trails,

Paul

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DrivingMissLazy
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« Reply #8 on: December 30, 2006, 05:58:21 AM »

I was thinking that if I ran into an air compressor problem while traveling could you hook up an 115 volt air compressor to this line to get home?
Jim
Jim, in a word... No.  We use shop air here to air up MCI's, and it takes sometime up to 20 minutes to get up to 120 psi.  MC-9's have such a large air capacity -- four large air tanks, ten air bags plus all of the associated plumbing.

If you are planning on taking a large compressor though, there is a way that it could be done.  Get a 1/2-inch or 3/4-inch quick disconnect and plumb it into the supply line at the compressor.  When needed, just hook up your emergency compressor to it -- it will still take several minutes to build air, but a large enough compressor should provide enough to let you roll.

Another option is to just carry a spare good compressor and change it out when needed.


John, it sonds  like you are confusing capacity with actual usage of air. I agree that going from completely empty it will take a long time for a small portable compressor to fill all the tanks on a coach. As long as it has adequate pressure, it will eventually fill them though.  Once they are full, then the small compressor will have little problem keeping up with the actual usage of air. And if it does have a problem then you pull over for a few minutes and let it catch up.

The main thing that I saw when I had to do this was that my inverter was not large enough to run the portable compressor and I had to run my genset, but that is really no big deal. I generally run it all the time to operate my A/C.
Richard
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John E. Smith
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« Reply #9 on: January 06, 2007, 06:38:06 PM »

John, it sonds  like you are confusing capacity with actual usage of air. I agree that going from completely empty it will take a long time for a small portable compressor to fill all the tanks on a coach. As long as it has adequate pressure, it will eventually fill them though.  Once they are full, then the small compressor will have little problem keeping up with the actual usage of air. And if it does have a problem then you pull over for a few minutes and let it catch up.

The main thing that I saw when I had to do this was that my inverter was not large enough to run the portable compressor and I had to run my genset, but that is really no big deal. I generally run it all the time to operate my A/C.
Richard
No Richard... the problem with MCI's is that they have several different interlocks in the air system, and very few things work when air pressure drops below 90 psi.  Even the fast idle won't kick in until 90.  Yes, brakes will work down to about 60 when the maxi's lock up -- but you won't have many systems.  And, if you have a newer MCI, even the air throttle won't work until 90 psi. 

With the huge air capacity, it takes a very long time to get the tanks up to pressure so that you can do anything, thats all.
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John E. Smith
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« Reply #10 on: January 06, 2007, 07:45:14 PM »

John, it sonds  like you are confusing capacity with actual usage of air. I agree that going from completely empty it will take a long time for a small portable compressor to fill all the tanks on a coach. As long as it has adequate pressure, it will eventually fill them though.  Once they are full, then the small compressor will have little problem keeping up with the actual usage of air. And if it does have a problem then you pull over for a few minutes and let it catch up.

The main thing that I saw when I had to do this was that my inverter was not large enough to run the portable compressor and I had to run my genset, but that is really no big deal. I generally run it all the time to operate my A/C.
Richard
No Richard... the problem with MCI's is that they have several different interlocks in the air system, and very few things work when air pressure drops below 90 psi.  Even the fast idle won't kick in until 90.  Yes, brakes will work down to about 60 when the maxi's lock up -- but you won't have many systems.  And, if you have a newer MCI, even the air throttle won't work until 90 psi. 

With the huge air capacity, it takes a very long time to get the tanks up to pressure so that you can do anything, thats all.

OK, thanks for filling me in John. Guess capacity is more important than I thought. For my Eagle, it seemed that my small shop compressor filled it up pretty quick.
Richard
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
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