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Author Topic: Getting water out of the air bags  (Read 1640 times)
Fredward
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« on: October 11, 2006, 02:55:46 PM »

I recently bought an MC-5A. When i bled the water out of the front air tanks, I got a lot of water. I've replaced the petcocks with spitter valves that I can reach from either side of the coach so there will never be that much water in there again. If there was that much water in the tanks, how much water is sitting in the bottoms of the air bags? Assuming a similar amount, how do I get the water out of them? Is there enough oil in the water that the bottoms of the air bag chambers won't rust?
« Last Edit: October 11, 2006, 02:59:23 PM by Fredward » Logged

Fred Thomson
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« Reply #1 on: October 11, 2006, 04:29:10 PM »

Some times the air tank acts as a knock out pot and catches this water, its hard to say when the last time anyone dumped the air on your bus, if its hard to access some just won't bother with it!  How big is this tank in gallons, and did you dump any where near that much water?   I don't know if  that much about MCI's, do they have dump valves on the air beams?  Good luck!

Pat
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NCbob
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« Reply #2 on: October 11, 2006, 05:04:49 PM »

Fred, I found that problem with my MC5A when I went to CHI to pick it up and, like you, it's been bothering me ever since.  That front tank (the one between the front wheels) is the service air brake tank and in theory shouldn't have and water in it.  Like you I have a cable pull dump ready to install and have since installed an AD-9 Bendix dryer...but I'm still getting moisture out of the 'wet tank'. Shocked

Un-nerving, isn't it?  I'll watch this thread with great interest and am sure is there's an MC5 authority out there...we might get the answers we're looking for.  But then you might wish to bounce it off the guys on the MC5 Yahoo Board as well.  Like here, they're a great bunch. Cheesy

We're, you and the other MC5'ers, are sorta like the Beagles running with the big dogs because we have smaller and older buses.
But fear not...we're just as welcome here as the big boys.  We were at a Rally this weekend and I was offered an Eagle for my 5...
so there's promise for us little guys yet. Wink

Hang in there...we'll get an answer yet.

NCbob
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NJT5047
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« Reply #3 on: October 11, 2006, 06:15:16 PM »

I recently bought an MC-5A. When i bled the water out of the front air tanks, I got a lot of water. I've replaced the petcocks with spitter valves that I can reach from either side of the coach so there will never be that much water in there again. If there was that much water in the tanks, how much water is sitting in the bottoms of the air bags? Assuming a similar amount, how do I get the water out of them? Is there enough oil in the water that the bottoms of the air bag chambers won't rust?

Bad news on the oil and water...the water will settle out on the bottom. Water's heavier. There shouldn't be much (any) oil in the air system either.
Don't understand NCBob's water issue. Sounds like the AD-9 may not be located between the tank and compressor? Could the air compressor have a water leak? A worn compressor will pass a lot of oil. Does the purge valve work?
I check my MC9 tanks occasionally, but don't get any water or oil from the valves. The awning hook makes a perfect tool to reach under the bus to the tanks.
Bob, not to change the subject, but, thinking about your power steering....have you checked the lines where they attach to the gearbox? You'll have to pull the spare tire out to do this, but it's gotta come out anyway.
JR
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JR Lynch , Charlotte, NC
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« Reply #4 on: October 11, 2006, 06:53:19 PM »

All buses with air beams and double convolute bags have corrosion in the beams and on the bag bottom plate. Completely dry air is just not possible on a bus system. The air bags on a MC-5 are fed from a separate tank so you can check it for water. If you want to check the bottom plate under the air bags you have to remove the nuts on the retaining bolts and lift the bag. Check the maintenance manual for the proper way to remove a bag.
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NCbob
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« Reply #5 on: October 11, 2006, 07:01:56 PM »

Hi, JR...No, as an answer to both your questions.  I've been busier than a cat covering 3 litter boxes since we got home and Ross and Buddy and the projects we're doing have taken my immediate attention away from the items in question.  Let's face it...when I go to the Bus Barn and those great big sorrowful eyes plead with me to go over and hug that rascal...all thoughts of work seem to vanish into oblivion.Q Cool

Seeing what you guys have done with your buses, and all the time it took, has made me understand that Rome wasn't built in a day...they worked on it a couple of nights as well. Wink

But...I'm pedaling as fast as I can...... Cheesy

Right now, we're working hard at getting a working water system in the bus...Ross is a great help and the Chief Designer.  What a joy to work with this guy...if I could just keep his eyes off the Hooter Gals! Grin

When we finally get to the front Service Air Brake tank...I'll be in a better position to answer as to why we're still getting water vapor after the AD9..in the meanwhile...patience, being a virtue I'm mighty short on these days, I bridge that cross when we get there. Wink

Bob
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NCbob
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« Reply #6 on: October 11, 2006, 07:05:23 PM »

And I forgot...JR...I replaced the compressor when I pulled the engine to replace the clutch...and the new compressor works great...

Unfortunately...it must be a female compressor..'cause it puts too many tears in the 'wet tank'.

Bob

And am I going to catch MOOOO for that comment!
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« Reply #7 on: October 12, 2006, 01:56:09 PM »

Hello.

Check your air schematic to see where the air suspension is fed from.

If you only had one tank with a lot of water, and the suspension is fed off the next tank, no worries. I would more worried about a slug of water rolling around in the brake plumbing, than the suspension...

The oil in your air system is not your friend. The blow by from the compressor is engine oil. It has combustion by-product in it, leading to an acidic/corrosive mixture in the tanks.

Air dryer will still allow some moisture by, its job is to knock most of the moisture out. Did you put a fresh desicant cartridge in it, or is the one that came in it used? Compressor passing oil? Oil will prevent desicant from absorbing the moisture. How is your air integrity? Lots of compressor run time? Typical air compressor will only dry around 10 cubic feet of air before the desicant is saturated, then the rest of the moisture passes through.

happy coaching!
buswarrior

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Fredward
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« Reply #8 on: October 12, 2006, 02:06:07 PM »

Yes, there was more water in one than the other; I'll check my schematics tonite - not sure what's fed off of which tank. I didn't know about the desicant cartridge where is that located? I see something resembling a small filter with a drain valve on the bottom of it mounted on the curb side rear bulkhead. It has a line coming from the compressor, I think.
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Fred Thomson
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« Reply #9 on: October 12, 2006, 04:38:42 PM »

The desicant is inside the air dryer and is a servicable item.

Fancy way of saying you have to take it apart and put in new stuff periodically, according to the duty cycle it has been operated under.

Your coach will probably have a moisture/oil trap in the line not far from the compressor, drainable inside the side engine access door. Sounds like you have found it already. It drains best when the compressor is pumping, and the line is pressurized to blow it out. When the compressor is cut-out, there is no pressure in the line. Often, the line has turns, so pressurized helps blow over the hills and around the corners.

Without knowing what it looks like, coaches also commonly have an alchohol evaporator mounted just inside the access door, mounted there on the fender or bulkhead. Small line in and out of the top, with a smooth metal can mounted below, no drains.

Also to consider, if you are planning to be where it is cold shortly.... you want to get this water thing solved, and may want to get the system doused with brake alchohol as a defensive measure.

My guess is your air system is fairly damp inside, and even the smallest lick of condensation inside the right brake valve will leave you stranded when it freezes inside.

You need that air system freshened up with some driving.

Now, there's some trouble.

If you have a stock alchohol evaporator, you can fill that up and get driving around town for a couple hours. You want to get some anti-freeze dosed air circulating around in an effort to get whatever moisture is in there to not freeze.

If you have an air dryer, get it serviced, both desicant and the heater.

If you have both, you have to worry. Has the air dryer been plumbed before or after the alchohol evaporator?  Often in a retrofit situation, found on everything built prior to the early 1970's, it has been plumbed after the evaporator. Trouble is that the alchohol is destructive to the desicant.

If you have no alchohol evaporator, do the next best thing, get the alchohol into the first tank through the drain valve. Make up something to get it in there: squeeze bottle, tubing for a gravity feed, whatever.

Your concern is getting alchohol riddled air through to the valving beyond the tanks. And you do that by sucking it through by using the bus.

happy coaching!
buswarrior

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Fredward
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« Reply #10 on: October 16, 2006, 07:10:39 AM »

Good information. I installed a "T" on the water drain for the wet tank and added a schrader valve. I plan to get an old freon tank and dump some brake system alchohol in it. Then charge it with air and use that to force the alchohol into the wet tank.

We used the bus this weekend probably for the last time this season and those front tanks didn't get any moisture in them although the wet tank did (which its supposed to). Living in Minnesota, things freeze real hard here. I store it inside, but not in a heated space so i don't worry about problems with freezing components not working, but would like to "evaporate" anything that is currently rolling around in there.
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Fred Thomson
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