View Full Version : Leans

dale farley
12-15-2015, 06:16 PM
The last couple times I've gone to Florida where the bus is housed, my bus is leaning significantly on the right side. I know this is an arbitrary question, but I'm wondering if there is a most likely spot that I should start looking?

12-15-2015, 08:50 PM
Sure, under the bus...

First, raise the tag and let the bus sit to determine if it's the tag. If it's not, check the following:
-- air bags
-- 5 port Norgren
-- 3 port Norgren
-- Most important the push-in fittings and bag ping tank fittings and drains.

Joe fixed mine last time and although he replaced the 5 port Norgrens, the leak was really a push-in fitting on the 3 port valve. My 15 year old 5 port valves looked and worked fine, but I had already ordered replacements.

Joe will hopefully chime in given he is the guru on Prevost air suspension systems.

Joe Camper
12-16-2015, 04:57 AM
Don't just raise the tag and see if the lean stops. First go all the way up with the port and starboard in level low then raise the tag and see if it goes away.

If u just raise the tag without doing this first the bus will squat down so much it will be difficult to see.

Do it as I suggested and the rear will settle back at ride height with the tag up also creating more pressure on the drive bags and if your leak is there it will also be multiplied. If it stops leaning it's the 2 position norgren or the tag bag or a line or fitting associated with those 2 parts.

If the lean is still there it's either 1 of the 2 drive bags or the 3 position norgren or their related lines or fittings.

Joe Camper
12-16-2015, 05:31 AM
Dale do u still pull your drives up on homemade wood ramps when u want to get under it??

dale farley
12-16-2015, 08:42 AM
Joe, I can do all the diagnosis inside the barn using my 4' pit, but I don't have much working room on either side of the bus. The area I enclosed for the bus was originally built to house a 37" 5th wheel. I can do a significant amount of the work under the bus, but some of it may be easier accessed on a concrete slab by my house. I would use the ramps if I need to. I built the ramps before I had the pit.

My ramps are 8 feet at the bottom and about 4' at the top, so both my drives and tags will fit on the ramps. I assume it would not be good to have the tags hanging down without support?

Joe Camper
12-16-2015, 09:35 AM
When u use the ramps and u pull up on them is it just the drive axle or is the tag axle also going on ramps too

12-16-2015, 11:09 AM

I've measured a few sets of ramps used by some of the conversion service centers. In all cases, the ramps where made to support both rear axles and they are intended to be driven on and not backed on. When determining how tall to make them you are limited on the ground clearance of the bus. Some drive the bus on some 2-bys to get the clearance they need before approaching the ramps. Some ramps were constructed with plated 2x8 lumber, others plywood, and others a combination of the two. Most had 1 or 2 pieces of 3/4" plywood attached to the top. The dimensions are generally 22" wide by 84" long on the part that the tires will rest on. The ramp part slopes to the ground 66" from the horizontal part. I didn't try to pick one up, but they must be heavy!

dale farley
12-16-2015, 12:28 PM
They are very heavy. I made mine in two 12" sections instead of one 21" section, so they would be easier to handle. I use a dolly to move them around, and I have handles on the side to use to slide them in and out. They are still heavy.

Joe Camper
12-16-2015, 04:30 PM
When building ramps it is imparitive they r long enough to get the tag axle up with the drive axle.

If u only elevate the drive axle u risk over extending the tag axle and potentially damaging things.

I have seen the top posts on the tag axle shocks bent and bent bad. I have seen the clevis and push rod for the lift diaphragm all bent up.
I have seen the gusset that attach the shock posts to the frame snapped free from the frame.
I have seen the arm the chain hooks to bent, it's post bent.

Joe Camper
12-16-2015, 06:58 PM
Dale when I first got my bus I built some ramps too.

Time has taught me I don't need them to make repairs. Even if I had them sitting there I would still not use them. They r quite heavy it makes getting the wheels up and down off the ramps harder than without ramps and if u elevate completely in level low and use stands that r max for your chassis when u dump and it comes to rest that's sufficient room to get around.

A pit that's another story very good tool.

dale farley
12-17-2015, 11:25 PM
I been under the bus a few times with the stands, and I agree that in most places there is plenty of head room.

dale farley
12-30-2015, 10:47 AM
I started the bus 6 days ago and let it get to ride height before measuring each corner. I checked this morning, and none of the corners have dropped over 1/4 inch. That's what I call an insignificant air leak, but I am wondering if my previous experience with the leans was because the temperature was much cooler when I was here in November?

12-30-2015, 11:14 AM
Air leaks that are associated with the push-on connectors seem to always be worse when the temperatures are colder. I don't know if the same can be said about the Norgren air control valve related leaks.

dale farley
12-30-2015, 01:44 PM
I've sprayed everything under the rear of the bus including all lines, air bags, tanks and brake chambers, and so far, the line on the side of the little tank in the picture is the only leak I've found. I turned the nut less than 1/8 inch and stopped the leak. I haven't checked the front yet.

I know I have a leak in the primary system, but I have no idea where it might be. I didn't see a problem with the brake chambers or connections in the rear. Haven't checked the front brakes or the emergency brake controller yet. I'm open to any suggestions about the leak in the Primary System Leak.

Joe Camper
12-30-2015, 06:39 PM
2 spots I come across more frequent than others that is cause for brake take air loss happening are the lines going to the gauges either at the back of the gauge or where they start in the compartment under the driver. Both ends r push in. These will be black 1/8 plastic, very small. The other place I've stopped brake tank loss more times than I can remember now is a 1/4 in black plastic signal line to a brake relay valve in the back way up on top of the drive axle where u would be challanged to even see it.

On the Hs if u pull the middle 2 house Batts from over the pass side rear suspension u can do it reaching in but only if you have long arms and a small belly.

On an xl no such luck it's up there. Even underneath u can't completely see it I replace it by feel.

Brake chambers r not going to be the reason for primary or secondary air loss with the bus off and the parking brake engaged.

dale farley
12-30-2015, 11:12 PM
Thanks Joe. That saved me some time and trouble.

dale farley
12-31-2015, 02:18 PM
I started looking for a leak at my emergency brake, and I have a significant one. Any time it is not turned a specific way, I can hear it leaking without even getting close to it. I can turn the whole yellow mechanism and it seems to stop.

I assume the only answer to this is to replace the valve? Does anyone know how much trouble this is?

12-31-2015, 03:35 PM
If you can get to it it is an easy cheap fix.

12-31-2015, 05:10 PM
Same thing happened on mine; has it replaced and everything was fine.

dale farley
12-31-2015, 05:17 PM
I removed the leather panel that covers the side of the metal compartment that houses the emergency brake and tag control. There was an inspection hole in the metal already, but it wasn't large enough to get to the valve, so I enlarged it significantly. There is very little play in the air lines, but I assume I can drop the valve and remove the lines through the hole I now have.

When the brake is engaged there is a constant leak out the exhaust port on the bottom of the valve. It is worse if I turn the yellow knob either direction. When I disengage the brake, the leak either stops or becomes so minimal that I can't detect it is leaking.

01-01-2016, 07:33 AM
Dale, what tool did you use to enlarge the hole " significantly. "

dale farley
01-01-2016, 09:56 AM

I made the first cut with a small air grinder (probably 2"). Although, the picture looks like there is ample working room, the first cut was very tight against the seat and seat belt bracket. I moved the seat forward as much as possible then turned it as much as I could. I enlarged the hole a little more with a small electric 4" grinder. Didn't have a cutting wheel so I used a grinding wheel. (As usual, my cutting wheels are in Huntsville with my other grinder.) I considered reciprocating saws, jig saws, etc., but my main concern was that I didn't cut any of the wires or air lines while cutting the aluminum. The hole looks rough, but it will be covered by the finished panel so it shouldn't make any difference.

I may end up cutting the hole even larger to have a better chance of working with the short air lines. Probably won't change the valve until I get back from Tampa since I can't even order it for a couple more days? It looks like two of the lines are push-in fittings and one is a screw on.

I don't know if Parliament sells that valve? If they don't, I guess I could have it shipped to their address?

01-01-2016, 12:24 PM
Any truck parts place will have one. There are plenty of places in Tampa. It's a PP-1 valve.

01-01-2016, 01:24 PM
Dale, we'll get a pair of them when you get down here. I need one also.

Joe Camper
01-01-2016, 05:01 PM
I would not get that valve from anywhere but prevo. I would not assume it is the same if that's what u r doing.

I'd make sure first if pressed.

Also that parking brake valve leaks 2 ways. When it's pulled up like dales leak OR they can be airtight when it's pulled up but leaking when u push it in.

IF it is leaking when u push it in and release the brakes there is a very good possibility what u r hearing is one of the diaphragms in one of the parking brake chambers gone bad and leaking back thru that valve at the drivers seat.

Don't make that mistake.

Kinda like when the exhaust port on the brake pedal under the floor starts a leak. It's probably not the brake treadle but rather the diaphram on one of the brake relay valves and it comes back and out the pedal.

01-01-2016, 06:46 PM
Hmm, leave it to Joe to throw the wrench of reality into our diagnostic procedures. Guess this is why we come to the Forum to learn and stay focused.

dale farley
01-01-2016, 09:51 PM
After discussing the issue with Joe, I'm pretty confident my problem is the valve itself. I'm not sure why it would make a difference where it came from if it is the same part number?

01-01-2016, 10:25 PM
The only differences between PP-1 valves is port sizes and the pressure they automatically activate at. I think Haldex makes 6 or 7 variants of the PP-1. FWIW, there is a rebuild kit for the factory valve.

Dale, I'm trying to understand how your valve was installed if the access hole has to be enlarged to remove it. On some coaches, like mine, the entire panel housing the valve is easily removed. On others the valve is accessed through the exterior electrical bay door.

dale farley
01-02-2016, 01:37 PM
I pulled my valve out just to make sure I can get to the lines to change it. There are only two lines (one to the Supply port and one to Delivery port) , Iso it looks like it may be relatively simple. That assuming I can get the push-on fitting off without a lot of trouble.

My valve is a Bendix 109221 PP-1, and it looks like many of the other Bendix PP-1 valves I've seen on the internet so hopefully there won't be a problem getting a replacement. The valve has a Supply port and two Delivery ports, but one of the Delivery ports is plugged. It is very easy to see why mine is leaking. The rubber O ring around the plunger is deteriorated and leaks. The leak is more pronounced when the stem is turned or moved in any direction.

My valve has 1/4 " Delivery ports and a 1/8" Supply ports. The pressure is 30 lbs. I checked with my local NAPA and they normally carry a Midland valve for $28 but are currently out of stock. The updated part # is Bendix 287417X.

Gil, I assume the picture below sheds more light on how I got mine out.

01-02-2016, 04:45 PM
CatView list the PP-1 for my coach as being one set to activate at 40psi.

The one I replaced mine with is this one (click here) (http://www.ryderfleetproducts.com/haldex-midland-kn20021/valve-dash-pp1-hand-operated-push-pull-parking-p-u55-kn20021). When I can get the rebuild kit I'll rebuild my original one and put it back in. Even though the replacement I installed is operationally correct, the clear plastic safety cover on the original one that helps prevent accidental release will not work on this replacement valve.

Dale, I still don't see how your valve was originally installed.

Joe Camper
01-02-2016, 05:01 PM
Gill on many xl chassis, mine included, prevo designed 0 access. For example on my xl no way u could get it from outside and on the inside the converter never needed in there for anything so I was the one that had to cut a 3 by 5 square opening in the inner stainless piece enclosing it to remove it.

Dales pics look very similar to what I had. Many valves r configured for multiple applications. Some have lower ports some have side many that come from truck supply have both so it works wherever. Not sure if a universal valve would fit but it might.

dale farley
01-02-2016, 05:24 PM

I saw 30 lbs printed by one of the ports, so I assume that is the pressure, but there may have been something else on it that I missed. I noticed on the Bendix site, the PP-1 has 30, 40 and 60 lb units.

The top picture shows where the valve is located in relation to my seat and left hand console. I will reinstall the clear cover once I change the valve. The 2nd picture shows the panel that covers the hole in the metal compartment. The left end of the panel covers the gray wires in the picture and the rest of it fits snugly against the lip of the metal compartment. The 3rd picture shows the compartment without the finished panel.

01-03-2016, 07:30 AM

A 30 psi valve buys you more time to get off the road if you have a major air system leak in the Primary or Secondary air systems. At the rated pressure the PP-1 automatically applies the parking/emergency brakes. You sure don't want to install one rated for 60 psi.

The panel my panel is mount to looks very similar to yours. In my case, I was able to remove that entire panel fairly easily. Sometimes it helps to be lucky, which didn't come my way for last night's Powerball.

Joe Camper
01-03-2016, 02:46 PM
Those numbers u r talking about r the "Crack pressures" .

I would never change them.

dale farley
01-03-2016, 04:45 PM

I wonder why that pressure would be different from one 98 chassis to another?

Joe Camper
01-04-2016, 05:54 AM
I would call prevo to be sure.

IMHO changing Crack pressure is not something that should be done. Maybe 1 of those 2 valves is not original.

Joe Camper
01-04-2016, 09:39 AM
Let's pontificate a bit. If the crack pressure is 60 when the yellow button pops up in an emergency type situation the brakes will have just begun to drag so they won't be too hot. They will begin to drag ,it's a guess but about 75 psi or so is my guess. So if the button pops at 60 the brakes shouldn't be overheated too bad at 60 and when they do set they will be able to do some good work.

So if the Crack pressure is 30 and the driver is unaware the bus is laboring due to a loss of emergency air and that could be for a multitude of reasons. Lots of horsepower, running on cruise control not a lot of time in the seat ect ect then when the button pops at 30 those brakes will be way way hotter and probably not work as well.

Design engineering r the only ones who should be knowing what's correct. If prevo had 2 different crack pressures for the same year chassis that would not suprised me and I would love to learn the reason why.

I guess 1 of those valves is wrong BUT Pierre IS still at loose in the factory so who knows.

Joe Camper
01-04-2016, 12:02 PM
Another thing Dale. That opening u uncovered. I think or I at least hope if a converter was putting in a access point it would have been done a little bit more professionally then your opening. Could that have already been replaced by a previous owner?? That opening is not what u would normally see in prevo conversions maybe th as t hole was done by a prior owner?

dale farley
01-04-2016, 06:12 PM

I enlarged that hole, and I think it looks veryyyyy useful!!! It is a little crooked, somewhat jagged, has sharp edges and is not pretty, but it works really good. I promise to straighten it up and make it look a little better before I close it up, but I feel sure, when the finished panel goes back on, the inside hole will look great.

There was a nice round hole in one end of the panel when I started, but it was unuseable for servicing the valve until I added my special touch. I'll try to remember to post a picture when I finish.

Joe Camper
01-05-2016, 05:42 AM
I wasn't trying to stab. I was trying to look for clues to understand why there would be 2 different valves in the same year chassis. I did not mean to offend u. I know u will let us know what u learn about it all.

dale farley
01-05-2016, 08:44 AM
Joe, No offence taken. Just being a little goofy myself. I am assuming my valve is original because I don't see any sign that it was changed before. The small inspection hole that was there would not provide access to change the valve, and I didn't see a quick/easy way to remove the metal compartment.

I took the Bendix part # off the side of the valve and called Bendix to verify the new number for exact replacement. The 109221 was replaced by the 287417N. The 287417X is the Rebuilt valve. I checked the Bendix website and found a local distributor who has the new valve in stock for $35 so I plan to get it today. My local Fleet Pride distributor (who is also a Bendix dealer) said they could order it for $55. The Bendix mfg said they had 109 in stock.

Joe Camper
01-06-2016, 05:39 AM
So what is the correct crack pressure for the parking brake valve on a 98 chassis? 60 psi or 30 psi and why did we uncover both on different buses of the same year?

dale farley
01-06-2016, 09:54 AM

I don't think anyone has a 60lb valve. I mentioned that the available PP-1 valves ranges all the way from 30 to 60lbs. Mine says 30lbs on it, and Gil said his is 40. The PP-l that Gil replaced his with is rated at 35 lbs +/- 10, so I assume the exact pressure is not that critical. That would also place his and mine in the same operating range. The one I purchased is the exact replacement for the old one, but it does not have the pressure stamped on it the way the first one did. I just know when I look at the Bendix chart, it says it is 30 lbs.

dale farley
01-08-2016, 11:34 PM

I enlarged that hole, and I think it looks veryyyyy useful!!! It is a little crooked, somewhat jagged, has sharp edges and is not pretty, but it works really good. I promise to straighten it up and make it look a little better before I close it up, but I feel sure, when the finished panel goes back on, the inside hole will look great.

There was a nice round hole in one end of the panel when I started, but it was unuseable for servicing the valve until I added my special touch. I'll try to remember to post a picture when I finish.

I installed the new valve today, and it is great to have no leak. The new valve also works (up and down) so much smoother than the old one. I sealed the hole then reinstalled the finished panel.

01-09-2016, 06:39 AM
Good job Dale. Although in the pictures the work area seems wide open when I look at mine I see how tight it must have been. It will be nice to not get the Brake Warning each time you turn the key on.

Joe Camper
01-09-2016, 08:11 AM
I couldn't do that in mine without taking the drivers seat out.

01-09-2016, 08:30 AM
You did a great job Dale

dale farley
01-09-2016, 09:45 AM
I couldn't do that in mine without taking the drivers seat out.

The valve replacement would have been easier if I had removed the seat, but overall it would have taken longer and been more work. A couple times I was laying upside down in the small area. Cutting the hole was the most challenging part and inserting the roll pin in the new valve was the second most challenging. It was difficult to see the hole for the pin, and I didn't want to tap the pin, so I used pliers to push it in. There was just barely enough room to get my shortest pliers in place, and I had to stand on my head to see the opening for the pin. This would have been easy if I could have tapped the roll pin in with a small hammer, but I did not want to take a chance on damaging the seal in the top of the valve.

I do understand that other configurations of seats could have made this impossible task without the removal of the seat. Mine was close but doable for which, I am thankful.

dale farley
01-12-2016, 10:11 AM
I don't know if it is possible that this leak (picture) could have been the source of the problem that I had in October with the bus leaning on one side, but it has not done it since I've been home for the last three weeks. It has been in the upper 20's and 30's several nights, and I haven't noticed any significant loss of air and no leans. I corrected this leak a couple weeks ago.

Since I replaced the emergency brake valve, I lost 4 lbs of air in the Primary system over a period of four days, so I think that is acceptable.

Joe Camper
01-13-2016, 07:50 AM
That leak at the fitting on that football tank was absolutely a lean. A small one but a lean none the less. Those r champaign bubbles OR a very slow small leak.

dale farley
09-30-2016, 09:42 AM

I think this is the thread you were asking about. The part about the emergency brake valve is on pages 4-10. You might be better off to start a new thread.

Joe Camper
10-06-2016, 12:03 PM
OK Dale better late than never.

I'm working on a 96 XLV Liberty. It has a massive air leak on the supply for the parking brake button. Like Dale my xl also had no access to this valve and I had to cut a opening as Dale did and expected to have to do it again on this liberty.


Mr Liberty in all his wisdom has redone this area and with a Phillips screw driver and a few min. U r looking at it.


If u look close liberty has shortened and blocked off the otr ac duct prevo puts those controls into and built a taller wider platform from wood.


Also when making this fix or going in to this area the button has a roll pin in the stem that is pushed out with a punch