MC5A settling too fast......

[Ncbob]

Y'know, Fred and Stan...that thought was working through the processes of my Neanderthal brain after I asked Stan for the part number of the check valve.....   but then in checking the Parts manual I discovered that there is a pressure protection valve. Now what that sucker does for or against me I haven't the slightest idea...but was wondering if perhaps that might be the valve which Stan was referring.

It has dawned upon me that no matter what I think...or which path I decide to pursue in the quest for the solution to my current problem (somehow I firmly believe that there will be more on my personal horizon) one of the items I will require in my 'bag of tricks' will be an ultrasonic leak dectector.  I have taken steps to acquire one.  As I was telling Ace the other day...I didn't need a 600# torque wrench until I removed both set of rear duals...then scratched my head and wondered why I hadn't bought one until now.

But, be that as it may, before I go much farther I will have more information than I have at this time and will listen dutifully to any and all offerings.  One of these days, providing I live long enough I,  like Jack Conrad, Fred Hobe, Jerry Liebler and a few others who are pillars of our Bus community, will be able to impart to others the wisdom of my experiences.

So, if you have an offering which might help solve my dilemma...I'll be more than happy to listen.

NCbob

[Fredward]

Stan/Bob,
The Check Valve I refer to is Mohawk part# 5549539 and it screws right into the leveling valve and the line to the air beam screws into it. My MC5 has one on each leveling valve. I was at C&J Bus here in the Mpls area ready to buy an airbag because I figured that was what was leaking. One of the mechanics there told me to replace this component before replacing the air bag. Low and behold, that corner of the bus quit settling. I don't know how it works Stan, because as you suggested, the leveling valve is bi-directional. But this liittle item did the trick. You can reach C&J Bus if you want to buy one. Otherwise, I'm sure you can get it from MCI. Mohawk is in Niles, IL 60714. C&J's phone number is: 952-881-0034 or 800-228-7349 (i've never tried that number). Ask for Yves or just ask for parts.
Fred

[Stan]

Fredward: I had a MC-5A for about ten years and I don't remember seeing a check valve on the bus air beams or on the air line diagram. I thinik that someone put the check valve in the line to solve the problem of a leaking leveling valve. There ia a filter (that looks like a small check valve) in the line that prevents dirt from the inside of the airbeam going back into the leveling valve when it is exhausting air (lowering).

If your bus has a check valve in the air beam line, the leveling valve would add air when additional load was in the bus. Not being able to discharge that air when the load is removed would have your bus looking like a kid's hotrod with a jacked up rearend.

[The High Lonesome Band]

Hello everyone,

I'm new to this site and already found it very informative.
Just wanted to introduce myself and say thanks for all the great ideas.

[DrivingMissLazy]

Hello everyone,

I'm new to this site and already found it very informative.
Just wanted to introduce myself and say thanks for all the great ideas.

Howdy Scott, and welcome aboard. I think you will find it a great bunch of guys and gals.
Richrd

[Ncbob]

Just a bit more information..FWIW.  After talking with Dick Wolfert, Christy and Larrys' saviour during their mishap after Arcadia this year, I put a block under the Left Rear radius rod and waited.   Surprisingly I held air pressure in the system almost all night Normally it leaks down in 30 minutes). While I haven't looked this morning (it's raining quite hard) I'm sure  there's been no appreciative settling.

I will have a definitive answer in about two weeks as I'll be taking the bus over to Dick and we'll chase this gremlin down and fix it once and for all.

Thanks for your input...but stay tuned for the final conclusion.

NCbob

[niles500]

NCbob -  We now refer to dick as SUPERMAN - show a little respect - LOL

[Fredward]

Stan,
You are right about it having a filter in it. And you are also right about it doesn't make any sense for there to be a check valve there (now that i think about it) but oddly enough the mechanic at C&J recommended replacing it first (cause its cheap) and after I replaced it she quit leaking down.........My left side settles faster than the right side so i was going to do the same thing to that side. Now I'm really confused.
Fred

[Stan]

Fredward: No need to be confused. Go back to the second post on page one of this thread where I told NCBob how to check for a leaking leveling valve. If a check valve in the beam air line stops the leak, then it pretty much has to be a bad leveling valve.

You can get a kit to rebuild them, but  most people just replace them. The check valve idea is a bandaid solution that may solve one problem but it creates another one (won't level properly). Many, many years of experience on many kinds of vehicles has taught me that it is not necessarily right just because a mechanic did it.

[Ncbob]

Just an update on an old topic...but last Monday I took the bus over to Dick Wolfert and put it up on his ramps.  Using an Ultrasonic Leak Tester I'd bought we quickly found that the Left Rear leveling valve was leaking. I had a spare valve but it turned out to be for the right side.  Fortunately Dick had a new valve for the left side so we compromised and installed both.  What the heck...the bus is almost 39 years old now and who knows how long parts are going to be around?

Sometime during the night everything went to hades and I almost got tossed out of bed. The whole left side of the bus was down!  Hmmmm...back to Dick's on Wednesday and up on the ramps again.  We checked and double checked everything he did and more.  There wasn't an air connection we didn't check with both the tester and soapy water mix!  The only leak we could find was a small inconsequential leak at the R shutterstat cylinder.

Strangely enough...now it seems that the front is settling on the left side overnight.  Please, before I buy a straightjacket, can someone throw some light on my problem?

NCbob

[Stan]

NCBOB: First, consider a properly working system:  The term leveling valve is a misnomer in that it determines the height of the body above the axles, not the height above the ground. The single front leveling valve only raises the front of the bus and helps to control the front to rear level. The rear leveling valves can raise the rear of the bus individually and so they determine the side to side level. That is. if you let all the air out of one rear side, the entire bus will lean to that side, even though the front system is working properly,

quote"Sometime during the night everything went to hades and I almost got tossed out of bed. The whole left side of the bus was down!  unquote.

  Do you mean that the left side dropped suddenly? Did both left rear tires suddenly go flat? Did you have a ground subsistance under the left rear wheels? Did your new leveling valve leak and let the bus go down slowly?  I don't know how well your ultrasonic leak detector works, but I am sure you aware that a common place for MCI suspensions to leak is through the top of the air beam under the wooden floor. This thread is so old that I don't remember all the previous posts, but the standard cure for a leaking beam is to put  plates between the air bags and the beams and connect the air line to the plates.

Give us some more information and we will try and help.

[Fredward]

Seeing as how I added more confusion rather than clearing it up: Brian Diehl was here on Sunday and he knows the check valve I am referring to. But it is ahead of the leveling valve, on the pressure side not between the valve and the air beam. Apparently standard issue on MCIs and prone to failure. Symptom of failure is leaking down. Fix is really simple but I had to remove the outside dual to get at it.
Fred (I was really starting to wonder)

[Stan]

Fredward: That checkvalve has a slightly different purpose. Normally, the bus will sit up on bag pressure for weeks or months if there are no leaks and the leveling valve is holding properly. One or two people getting into the bus will not cause the leveling valve to open. It has a fairly wide dead spot at the center position. If the bags leak down (or a large amount of weight is added to the bus) the leveling valve opens to the supply, to add air.

If there is no air pressure in the supply line, the checkvalve you refer to prevents the bags from leaking back into the supply tank. If your suspension and leveling valve are not leaking, this checkvalve will normally not come into play.

[NJT5047]

Bob, do you have airbeams?  I'm not familiar with '5s but, airbeams will leak and you cannot ID the leak.  Often on top of the beams.  Simple fix if this is the problem.  Relatively simple to fix. 
Stan has already described the function of the leveling valves...not much to add there...but if the LH side is dropping, it's due to the LH rear airbags or related components...not the front.  The front may be leaking down too..or they are properly inflated and the LH rear is allowing the bus to tilt. 
The front airbags can tilt to the stops with 60 lbs of air as the front airbags are "T'eed" together. 
Have you considered isolating the drive axle airbags?  Install some valves so that you can turn off the aircharge when the bus is level to the drive axle.  Then, if it leaks...you have your problems isolated.  If it doesn't leak with the valves closed, the leveling valve or check valve is leaking.
You could air it up, shut the valve off, and drive it if necessary.  If it leaks down, open the valve and it'll air up.  And, you'll narrow down your leak.   Old airbags can leak and be difficult to ID...they sorta "seep."
Keep us posted on your progress!
Don't let Jackie fall out of bed!   
JR 

[Ncbob]

Do you mean that the left side dropped suddenly? Did both left rear tires suddenly go flat? Did you have a ground subsistance under the left rear wheels? Did your new leveling valve leak and let the bus go down slowly?  I don't know how well your ultrasonic leak detector works, but I am sure you aware that a common place for MCI suspensions to leak is through the top of the air beam under the wooden floor. This thread is so old that I don't remember all the previous posts, but the standard cure for a leaking beam is to put  plates between the air bags and the beams and connect the air line to the plates.

No, the left side doesn't settle quickly (like a  blowout) it takes a while...like overnight. And I did NOT take up the floor before building the bedroom...no reason to question the settling thing.  It seems that the bus settles more when we're aboard...that is..just our walking around probably makes the air valves ask for more air and when there isn't any it settles.

I didn't see any check valve when Dick replaced the valves but did note the screen adapter on the air beams. It appears the the line from the wet tank goes to each air valve. Unless the check valve is built into the air valve on the inlet side I have no idea where it might be.

Too, after having been on the road, I believe the bus height above the road is the same on both sides.
There is also a 12.5 KW Kohler genset on the left side of the rear bay...that too probably adds to the left side settling.  That is going to be removed and sold this spring in the hope it will help a bit.

Thanks to all for their input.

NCbob