My first lean

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Woke up in very cold Boston this morn’, first of the new year. Bus was leaning low on the driver’s side. We drove through heavy snow yesterday and it was 5 degrees last night. Not sure if that could have had anything to do with it. Lost of frozen road crud caked up under the coach. Will wash it all down when we play in Virginia next week, but for now, it’s just falling off in big, frozen chunks.

So, I can air up the coach just fine, but after an hour or so, it’s leaning again. Front is holding, curb side is holding, driver’s side is dropping. Where do I start troubleshooting this problem. Could be any number of things, right? Bags are pretty new I think. Just had them looked at a week ago as well.

Driving down the road, no problem. Only notice it when I’m parked.

Any suggestions of where to start?

Thanks. And Happy New Year to you all!

~Adam

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Adam,

Cold weather brings out the first signs of the leans. When you get to warmer temps the problem may temporarily go away. Or not.

The snow and ice has nothing to do with it.

If the bus continues to lean as you describe, especially if it starts to lean within a relatively short period of time that is actually good news. It means you are not chasing an intermittent problem. It forces you to make a decision however.

You can ignore the problem until it just becomes a royal pain in the butt. The longer you ignore it the more likely it will start losing air on the other side or in the front. The bus components are aging and will need to be replaced.

The decision you make however is to decide if you want to fix only what is now causing the problem, or to recognize that everything else under there is aging as well, and you may decide to just get it all done all at once. Since there are a number of us that have done things both ways, you will not lack for opinions on which direction to go.

To address your specific problem it could be a leak in one or more of the air bags on the driver’s side in the rear. Air bag leaks can be very hard to find unless you have lived a clean life. In that case a few minutes with a soapy spray and you or the tech will see bubbles. Don’t count on that however because some leaks will never show up with soapy water, a stethoscope or an ultrasonic leak detector because there are places you cannot check with the air bags installed. If you get to warmer temps and the bus stops leaning or at least takes longer to lean, my educated guess is to ignore the air bags and concentrate on the three Norgren valves that control the driver’s side rear.

My first guess is the problem lies with the 5 port Norgren located on the bulkhead ahead of the drive axle, driver’s side. My second guess is the 3 port Norgren located up on the frame between the tag and drive axles. My third guess is it is the 3 port Norgren located in the steer compartment.

Here is where your decision making gets complicated. If you bring the coach into a shop you are a mere civilian, and as such the techs will ignore your opinion unless you direct them to replace parts and not try to analyze the problem. Without testing, replacing parts is a crap shoot. Squirting soapy water and listening through a stethoscope takes as much time (translated that means dollars) as it takes to just replace the parts.

My advice: Get a guy like Joe C to meet up with you and have him change out all components in the affected area. He or you can buy them as cheap as anyone else and unlike some shops that make you pay the learning curve he will get the job done and you will pay far less than anywhere else.

If that is not practical, since your Norgrens and air bags are likely near the end of there trouble free period in life, replace them, starting with the rear 5 and 3 port valves.

It could be other problems like leaks in fittings or air bags, but if it has been OK up until now, and warmer temps make the problem go away or less severe, then the two valves I mention are highly likely to be the problem.

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Adam the one diagnosis you can make from your drivers seat is raise the tag and wait. If it cures the air loss it is the rear three port valve and if it doesn’t you can then rule it out.

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Joe and Adam,

Good advice. Adam, just make sure if you do that that you run the bus engine and raise the pressures enough so the rear comes up after lifting the tag. When you lift the tag the rear will squat, so bring it back up before you shut down the. You can’t see the bus lean if it is sitting down to start with.

Forgot to answer a question you raised. The leans as you describe are not an issue as you drive. Your engine driven compressor will handle small leaks easily, but if the leak turns out to be in an air bag and gets increasingly larger that may pose a problem. You will hear air escaping if that is the case however.

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Jon
What is the ~cost of replacing all the norgren valve? I know you repair yours can a person just replace the o-rings or is it cheaper ( cost and time) to just replace?
GregM

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Depending on which Norgren the whole valve costs just less than $60 (3 port), or a little less than $120 (5 port).

Regardless of which valve it is the replacement time is a constant. If you allow 30 minutes each once you get under the bus that is a safe number. If you or the mechanic work slow, call it 45 minutes.

The exception is on older coaches that have the 5 port Norgren ahead of the drive axle fender liner. Then the cost to access it increases and adds about another 15 to 30 minutes to the R & R.

Rebuilding them is something for the owner/mechanic to do. I rebuilt every one on my first coach. One a night after work until they were all done. I removed them, cleaned them as good as I could, disassembled them, replaced the spool and then bench tested the assembled valve with a rig I made up of parts from the local hardware store. If you are paying someone to do the job that is just not cost effective because the amount of time spent doing that at the $100 an hour typically charged will pay for a new valve.

For the owner however it is a nice way to spend an evening, not real productive, but very satisfying when it all works after you are done.

The only caveat is that if the air system has not been maintained and the system has had moisture in it the bore on the valve body may have become pitted and is thus useless.

This past time I replaced them and saved the removed valves. Some weekend I will either replace the “O” rings or the entire spool assembly, bench test them and have them ready to go when I need to replace them again. I bought the spools from a Norgren distributor and the best I can recall is that they were fairly cheap compared to the cost of a valve ($10?), but a lot more expensive than just getting “O” rings.

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Thanks Jon
I was going to do this myself, so it would time plus cost of parts.
GregM

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Greg,

I don’t place a value on my time. I treat working on the bus as a hobby and not something to track how much money I save (or spend).

If you approach yours the same way then your parts cost will be “o” rings or spools. You will need to bench test completed valves. The way the Norgrens are designed and what makes them ideal for this application is they can be pressurized from either direction, unlike a typical valve with a washer type seat.

In our buses that is exactly how the valves are used, sometimes holding air from the air bag side and sometimes holding air in the opposite direction. When you bench test you have to check that they are bubble tight in each direction and also that they do not leak sideways past the “o” rings out the end caps (which are not sealed.) You will see and understand what I mean. The valves are very simple and you will quickly see how they work.

The only thing remaining will be to check the solenoid manifold in the steer compartment. That assembly may make you lose aux air, but even if they leak they will not cause the leans.

Good luck.

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The 5-port regardless of location are easier to get at than the 3-port that feeds the tag bags. The first time I pulled them I did a lot of talking to myself. Get yourself in the right frame of mind when you go for them.

Jon don’t forget the early 90’s stuff will dump the tag bag air if the aux air goes down and IMO the ease of replacement and low cost of that 3-port in the steering bay warrants its replacement.

Although loosing the tag will not make you lean it will get you unlevel just the same.

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Joe, Short people shouldn’t be asked to change the three port valves up on the frame. That’s a real stretch.

Have you considered sitting on a cushion when you are under there?

[MyPrevost]

Joe, Short people shouldn’t be asked to change the three port valves up on the frame. That’s a real stretch.

Have you considered sitting on a cushion when you are under there?

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Hey guys,
thanks for your help. Joe, I’d love it if you would help me with this for many reasons: it would be nice to meet you in person, the job would get done right, and I’d be able to watch/learn/assist so I could maybe pass it on one day. I realize we may not be in the same place at the same time, so maybe we can coordinate and figure it out.

Incidentally, the problem is getting better now that it is up to 30 degrees. Haven’t done the tag lift test yet though. But I like the idea of just replacing all of the valves and giving my coach the full valve rejuvenation therapy.

So Joe, where are you, when are you? And Jon, thanks for the detailed response. As always, super helpful!

See ya on the road.

Adam

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Adam,

As a preventive maintenance measure, since our bus is at the 10 year mark, we have decided to replace the six rear air bags, 5 port Norgren valves (2), 3 port Norgren valves (3) and 2 ride height valves.

While we’re in there, the 2 drive axle and 2 tag axle brake chambers will also be replaced.

Luckily, the shocks appear to have been changed.

The front bags were changed last spring.

In my opinion, at this stage of life for our bus it makes sense to simply replace a many components as are realistic to access at a time and try to eliminate chasing problems down the road.

Oh, and Joe will be performing the surgery…..

I’ll keep ya posted as to how the “shotgun” approach worked out.

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Paul & Joe, our 2000 Liberty has quick-fill tanks for each bag that get air in series (sequence?) beginning with the 5-port valve. Our left rear leaks were in the drain valves for those tanks. Those should probably be reseated or replaced also. A very inexpensive part. Adam, ours only leaked when cold. Don’t know if yours is set up this way or not.

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Jim brings up a good point. Adam’s coach will not have those tanks however due to its age. But that is a good reminder to Joe because Paul’s bus does have the tanks.

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