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Do I have a problem or is this normal?
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Hi Jim, Yes that’s where it’s located. Seeing it today I was surprised how clean it is with no dust or residue on it. You can tell from the picture that the brass fitting the knob is attached to looks new as well?
What do I need to do and can I continue using the bus? All air gauges on the dash are where they should be as are the heat gauges. But it can’t be good if it handles the tension on the belts?
Harry
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Sure looks like a new valve so my money is on the cylinder o-rings.
you can drive it just put it on the list.
i’m out of pocket and don’t have the air diagrams but I don’t thing I’d plug the vent port. That could lead to the same pressure on both sides of the piston and therefore not keep the belts tight. As is you have 75 psi on the piston and the belts will be tight. You just have leaks past the piston and out the vent.
a least 4 years ago Prevost still have the o-rings available.
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Harry,
That is the valve I was referring to back in the beginning of this post. The purpose of the valve is to allow you to release the air pressure on the belt tensioner cylinders so that engine belts can be removed and replaced. The valve should be set at the closed position (not leaking air) for normal operation. Someone may have bumped it causing the leak.
I suspect that it was replaced by Jeff since it looks so new. Just close it and you have solved your first leak!
Best,
Doug
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Until Harry takes the time to explore how that works, and why, he wants to be certain that moving the valve is not going to leave his belts loose.
The valve, pressure regulator, and cylinders are all candidates for leaks.
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Harry is that valve down or overhead? Mine is up right between center of doors. Have to reach up to reach it. It’s hidden unless you know where it’s at on mine. Had a level 3 done in Houston a few years back and pulling car back bus started heating at cruise speed. Slow down and it would cool down. Belts were turning and looked okay. Limped it home and the Guy that helped with it found out somebody had released pressure and belts were slipping.
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Hi Glens, Mine is in the same place above the doors. Jeff did replace it when I was there but I still don’t know if releasing air is normal when shut down? Jeff asked if it released air while the engine is running but how would I know? There’s a lot of air moving around back there, I’ll have to see if I can tell by putting my hand up there.
Harry
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Harry mine doesn’t dump air when I stop engine. Don’t think it should. Want to keep all air you can in system to keep belts from flopping on start up.. I figure the original valve on mine and any of them will have some kind of dump to release pressure on cylinders to change belts. Might just have a faulty valve.
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What would you do about this Glens? If the handle is fully closed it expels air. If I turn it down a little the air stops. Maybe it’s obvious but I’ll ask anyway… Should I turn it until the air stops?
This was just installed so you must be right, it’s a bad valve.
Harry
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Looks like dump valve beside it and it could be malfunctioning also. Would replace both and see. Don’t think I’d run with valve not full open (inline to cylinders) . Does your belts feel tight. Do you still have belt guards in place?
Also valve in that position it looks like it’s going to dump.
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That valve is designed to be either “ON” meaning air is directed to the bellows (cylinders) that tighten the belts, or “OFF” meaning all air is exhausted and the belts relax so they can be removed or replaced.
This doesn’t need to be a complicated discussion. If air is heard find out where it is coming from. It is either the valve or pressure regulator or one of the fittings. Spray some soapy water and look for bubbles. Whatever leaks, fix or replace.
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I’m confused… Didn’t we already identify the air is escaping from the valve with the red handle? In the full off position (the position ETLC put it) air is escaping. If I turn the handle down a little the air stops, if I continue to rotate it down to the bottom position the air comes out and is much greater. So either way I need to take the bus back to ETLC.
Glens, I didn’t take the belt covers off yet. I was waiting until November 1st when I move the coach to its new location where it will be easier to work on.
This valve has nothing to do with Jake brake right?
Harry
1984 96" with 8V92TA
(remodeled Liberty Coach)
Greenwood, MO -
Take it to someone to diagnose and repair it.
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I usually read every thread that might put a little nugget in my brain for future reference, but this one is timely. Yesterday I fired up my coach and encountered this exact symptom. I just returned from a 2000 mile trip two weeks ago, and hadn’t noticed this before. I can’t really say when it started though.
Mine also leaks in the closed position, but seems to stop completely when turned 10 or 20 degrees toward open. The open position definitely still expels air. The air that leaks when the handle is in the closed position is coming out through the “dump” port on the valve. I’ll be sure to report back on the source, but it appears to be an internal leak in that shutoff valve.
(Since Jon is reading this thread – I just noticed that my signature now includes a picture of a nicer bus. Is that a result of the board upgrade, or did I win a prize?)
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Harry my valve is point down and I have no issues with the belt(s). I did have an issue years back with the fan hitting the radiator shroud and found out the belt was longer than the original. Went through two fans before finding this out. I didn’t know the belt size at the time of service, but figure the bus mechanic knew what he was doing. Wrong.
Harry with the bus aired up turn that valve to different positions and see if the belt tightner moves. The position where the belts are the tightist is the right position. As Jon says, there is not in-between position, it is either on or off. it should be in either 12, 3, 6 or 9 o’clock position, anything in-between is off.
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Chad and Greg, thank you both so much for chiming in. I believe it’s about the 3 position on mine where the air stopped. But how does all this work, air is not supposed to come out in the closed position but it does.
If it stops at 3 as discussed above should I leave it that way and I’m good to go? Or should the valve be replaced. It’s a new valve as you can see, so what would you do?
Thanks so much for posting!!!
Harry
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