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JIM KELLER
08-06-2014, 09:41 PM
For years I have heard about a check valve that would stop the belts from loosing tension. I have wondered what I would do if I had to move the Bus in an emergency and didn't have time for the Aux Compressor to build air before starting the engine. Well, I finally found the valve and replaced it. On a scale of 1 to 10 [ with 10 being the most complicated ] it was about a 3. It is a one way check valve mounted on top of the red handle assembly we turn to release the pressure on the air bags to change belts. About one inch long with male threads on each end. This small little one way check valve has a arrow on the side for the direction of flow. Install the valve with the arrow pointing towards the flow of air to the air bags. My Aux Air system is not completely leak free and leaks down after several days but my belts are now still tight. This was such an easy repair I don't know why I waited so long to investigate and repair. Part was about 50.00 from Prevost. If anyone is interested I can find the part # and post it when we are back in Florida.

dale farley
08-06-2014, 11:35 PM
In addition to the inconvenience of having to wait on the air to fill the bellows, this fix should also diminish the other problems caused by inadvertently starting the bus before the belts are tight. It is easy to throw those belts off or even stretch or break them. Good idea Jim. I would ask you to post a picture, but I know you sometimes have trouble with that camera!

Gil_J
08-07-2014, 07:24 AM
Yet another one of those things on my to-do list. If these were on my honey-do list they would have been done long ago.

Bill Dator
08-07-2014, 07:39 AM
Jim, Thanks for the information. Knowing my problems with belts this seems like something I should do (or have Prevost do) what is the disadvantage? and why didn't Prevost install this valve originally. Hope all is well

Joe Camper
08-07-2014, 08:24 AM
If there is a leak in the belt tensioning bags that but will keep air in them if the aux air pressure drops.


Can u still release the bag pressure with the red pointer? How does that happen with a 1 way valve in place?

Gil_J
08-07-2014, 11:36 AM
Joe, the check valve is located between the pressure regulator and valve and the aux air system. It has no effect on the regulator or valve. I understand that not all coaches have the factory installed check valve. For those of us with aux compressor it's a good idea to air up the aux air system before starting the engine.

FWIW, the engine mini bags don't last as long as our suspension bags. One is easily replaced and the other is a PITA. I let Prevost do the work.

JIM KELLER
08-07-2014, 10:23 PM
Jim, Thanks for the information. Knowing my problems with belts this seems like something I should do (or have Prevost do) what is the disadvantage? and why didn't Prevost install this valve originally. Hope all is well

Bill, There is no disadvantage. On my Bus and I think on yours the valve was installed by Prevost. It is mounted directly above the red handle you turn to release air pressure for the belts. It is so small it is hard to see. It simply gets dirty with debris from the air system and quits working after a few years. My belts are still tight days after the Aux System is empty. Maybe some day I can get Hector to show me how to find my leaks.

dale farley
08-08-2014, 08:01 AM
Jim, Please give us the PN for the check valve.

rfoster
08-08-2014, 11:02 AM
That is a great idea Mr. Keller.

Bill Dator
08-08-2014, 11:02 AM
Thanks Jim, I will look for it and advise

JIM KELLER
08-08-2014, 07:38 PM
Jim, Please give us the PN for the check valve.

OK, When I get back to Florida and find the invoice I will post it.

JIM KELLER
08-10-2014, 07:18 AM
Jim, Please give us the PN for the check valve.

Dale, The Part # is 530175 for 44.56. It is on an invoice with other parts and they listed it as a Fuel Line Checkvalve. I think they labeled it incorrectly. Can you check the Part # and confirm ? I don't have access to the Prevost parts database.

jwhitacre
06-12-2015, 10:56 AM
I found a small leak in my tension bag. Anyone have a part number, or where I should start looking? i'm in Flagstaff headed back home to Tulsa and hope it makes it.

Gil_J
06-12-2015, 07:54 PM
Jackson,

Almost all of these mini air bags leak a little. Sometimes tightening the clamps on the base of the bags helps. Small leaks won't effect their operation. The air system can overcome small leaks.

Call Prevost parts and order them. They are competitively priced and they don't charge shipping for standard shipping. They are surely in stock in Ft Worth, so they would ship from there.

dale farley
06-13-2015, 10:24 AM
I haven't started the bus for about 3 months now. This morning, I turned on the aux air and let it build up and shut off at 85-90 lbs. The belt tensioner pushed the belts out about 3/4 the way, but it never tightened them completely. I started the bus, and when the pressure went over a 100 pounds, the belts tightened up completely. Is there a valve in the line causing this??????????????

JIM KELLER
06-13-2015, 09:14 PM
Dale, I'm thinking mine tighten up around 60 psi.

dale farley
06-13-2015, 10:00 PM
I think mine normally tighten at about 60 also, but that wasn't the case this morning. Don't know what could have caused the delay in it tightening.

Donnie Myers
06-15-2015, 10:17 AM
You could have a pressure protection valve sticky and only letting a small amount of air pass. You could have a sticky belt tensioner check valve (which is indeed a fuel line check valve) or the tensioner could be corroded a little.

dale farley
06-15-2015, 01:15 PM
Thanks Donnie. I'll try to find these valves you are referring to.

Gil_J
06-15-2015, 02:34 PM
Dale,

Where are you reading aux pressure?

My first thought is that you are reading pressure at the aux compressor. If your aux compressor is set to 85 psi, then you shouldn't expect it to turn back on until the pressure drops to 65 psi. 65 psi will put you very close to the protection valve pressure setting. So, air was being supplied to the Prevost Aux system until the pressure dropped to the pressure protection valve setting. This should be 60 - 70 psi or there abouts. This resulted in some air making it to the engine air bags, but not enough before the protection valve kicked in. Your compressor didn't cycle back on because the compressor kick-in pressure is slightly above the pressure protection valve setting. Again, all speculation on my part based on your limited symptons.

Before you take off the pressure protection valve try this. Drain the Prevost aux tank under the front end. Drain the engine bags. Start the aux compressor and see if you get the same results. If so, drain the aux compressor at the compressor just enough for the aux compressor to cycle. If this results in the engine bags making it up to there regulated pressure, you don't really have a problem. If this worked and you want the compressor to cycle below the protection valve's rating, increase the aux compressor's cut off pressure to 95 psi.

Donnie Myers
06-15-2015, 07:01 PM
I haven't started the bus for about 3 months now. This morning, I turned on the aux air and let it build up and shut off at 85-90 lbs. The belt tensioner pushed the belts out about 3/4 the way, but it never tightened them completely. I started the bus, and when the pressure went over a 100 pounds, the belts tightened up completely. Is there a valve in the line causing this??????????????

I have to apologize. Today I read this from my phone and totally missed the part about you starting the aux compressor. I only read starting the coach, its been a long week..lol Your pressure gauge is probably getting tired and needs checked. I personally like to set the cut in at 60 and out at 80. This is usually adequate for belt tension yet lets the compressor run the shortest amount of time therefore extending its life and keeping as much moisture as possible out of the system. If the gauge is accurate, I would still check the tensioner regulator as it could be gummed up. 80psi is more than enough pressure on the belts to start the engine.

In reality, you should find the leaks in belt tensioning system and fix them. With the check valve working properly and no leaks, your aux air should be able to go to zero and not have to worry about the belts loosening up.

dale farley
06-18-2015, 08:25 AM
Gil & Donnie,

I was reading the initial pressure from my Aux air gauge on a panel over my windshield. At this time, I have not been able to duplicate the problem, so hopefully it was a fluke of some kind. I'll see what happens the next time I start the bus. I do need to find the leak in the belt system, because it will leak down in a few days. Thanks.

JIM KELLER
06-20-2015, 06:32 AM
Dale, have you replaced part # 530175 yet ?

dale farley
06-20-2015, 10:34 AM
Jim,

I don't think I have replaced that part. I see you posted the number a year ago, and that was about the time I was migrating to Huntsville, so I probably let it fall through the crack.