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RR8S chassis leaning on air bags after shutdown


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New to us 2004 HR Scepter, RR8S chassis, 8 air bags. Picked up this Monday and once in storage bay, MH driver side lowered many inches in a few hours time. Very noticeable lean.  I believe that the coach was always on its hydraulic jacks at the dealership and did not notice this. Did not really notice any air hiss. Did some research early this morning and only got to the air dump valves could be rebuilt with new o-rings b4 our internet went down. Spent day at coach working on little things. Installed a 7" monitor on dash that is dedicated to the Aladdin system. Seems to be working great and will write up the install.  Before lunch, I decided to bleed the air tanks and air bags down. Drained system to around 30 psi twice, recharged to 120 psi and left for lunch. Some settling of driver side during the next 4 hours, maybe 1/3 of the settling that occured yesterday afternoon. 

I have one ride height valve for the front axle and left/right for the rear axle.  My assumption is that the driver side rear pair of air bags is bleeding down. I think that means the leak is on the air bag side of the leveling valve. As the front has only one leveler valve, the air will transfer from driver to passenger side and tilt based on the rear bleed down. Is this a good assumption?

Slid under coach and looked at rear leveling valves. First big surprise is that air lines are in the 1/4" range. I had expected much bigger. There is what appears to be the tank supply going to the leveling valve on the side towards center and 4 lines connected to tees on the discharge. Each corner has two air bags so two line. I figure a line goes up to the air dump valve. Maybe I miss counted because I haven't come up were the 4th line would go.  I thought I saw the dump valves mounted high above the differential by following an air line but when I looked at the front axle, it was easy to see that the similar front valve I was looking at had a big, maybe 5/8" line going to the disc caliper. probably looking at the wrong valve.

Can some one give me a heads up on what the air dump valve will look like. Is there a repair kit or someone selling o-rings?

I picked up a bunch of 2x12 short pieces on the way home to see if I can get the coach up 3" or 4.5" tomorrow to feel better under the frame. 

As I said, I didn't hear hissing earlier. As I was pulling tools out to go home, I noticed an air leak hissing at the front.  Dropped from 120 psi to 90 psi in 10 minutes or so, both tanks. Recharged air and slid under with a spray bottle of simple green (what I had available) and sprayed most of the fittings with not any bubbles. There is a lot of stuff hanging low under the coach at the front so could not get hands on to the tank and lines. I expect the 2 X 12s will help raise it up so I can see.

The tank has two approx 3/8" diameter hoses coming out of the bottom.  I was expecting a drain. Is one of these a drain of sorts?

Are diagrams available of air lines? Looking for what help I can get.

Thanks,

Mike

 

 

 

 

 

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I feel your pain. We purchased a 2008 Dynasty with 10 bags. It would drop all the air from the left side in about an hour. I made ramps from 2x10's to drive up on. Spray bottle full of water and Dawn dish soap. Heavy on the soap so any little leaks will show up. Be patient. Over the next 3 days we found 16 air leaks. They were all very small leaks and did not make a sound, Not one bag was leaking. All the leaks were from the cheap quick connect fitting, regulators, and connection/threads on the air tanks. I would recommend buying numerous brass DOT approved compression fittings or various configurations. Tee's, elbows, couplings. I have air leveling, no jacks so air leaks are a problem. Good luck and keep looking. you will get it handled.

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Print this out. I think this will be a great help.

 

Mike

I know that getting the end of the tubing square when cutting without burrs.  Wondering if the PVC tubing cutters would be a good way to trim off a little to restab fittings?

 

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Mike, this site has many downable files which can help you. I had several files printed at 48" X 36" so that the details were readable, (not so when blown up on my monitor), and I could keep them with my RV if needed. As you probably know high end commercial printers use algorithms which will print a pdf file at that size without image degradation.

"Mountain bikes as toads"  Bikes are my preferred toad. I only drag a vehicle around as a last resort. Sometimes I just plan on using a taxicab a few times if necessary. The cab fare is minimal. My winter project is going to be hydraulic rear lift for a motorcycle. 

Good luck on your new RV.

Edited by Gary Cole
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Dr4Film, Thanks for the diagrams. Printed on 8.5 by 11 they were pretty small but a chart magnifier left over from the boat let me see how many of the lines were run. Gary, I agree with printing off to a bigger size to have available for reference. Good day working on the coach. Oklahoma has been almost 10 degrees cooler than a normal August so a little easier to put in 8 hour days. Blocked front wheels up 4.5" and slid under looking for leaks. Turns out it was the high pressure relief for the forward tank. Old style with a cap at the end held closed by a spring. $35 and a new, better designed 150 psi relief in place. After replacement, maybe dropped 5 psi over an hour period of time. 

Line plumbed to the leveling valve on front axle pretty easy to follow. Tee on discharge of valve. Line to driver side runs to frame rail and a tee feeds front and back forward axle air bags. Line to passenger rail tees with the thru run port going to another tee and supply front and back forward axle passenger side air bags. The first tee (on passenger side) branch port had a line that ran back across the frame to drivers side frame rail and then ran up into the area in front of the "firewall". Pulled out generator and there was the single solenoid valve shown in picture. Wife discharged air and vented thru screened plug on exhaust port. Sprayed with dawn mix and no bubbles. 

RR8S is side radiator giving good access in rear compartment. Lots of wires so had wife hit the air dump switch. Found under a wiring harness the two valves pictured side by side. Vents are pointed up so easy to load up with dawn mix. No bubbles over a 5 min watch. These solenoids are on the right bulkhead pretty close to the corner where it turns to become the actual engine compartment.

Very pleased with the reduction in time for air to come up to pressure. checked a couple of dozen fittings with dawn mix and did not see any leaks. Pleased with the mornings work. The plan is to pick up another relief valve for the rear. The new type has a long body with a hex fitting to install.  the poppet is within the ID of the fitting and is better protected from grime. Bendix 800350 ST-4 safety valve

Hope maybe this helps someone else understand their system.  

Air cylinder and brackets came in so will be replacing the door stay lever over the next couple of days.

air dump solenoid foward.JPG

air dump solenoids L & R rear.JPG

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I did find an air brake safety relief at NAPA for under $16 but it is the same style as what I had.  MBI KN31200. Looking at the air diagrams Dr4Film sent me, which is a different coach but was very similar to mine, the compressor feeds the forward tank and then to the rear tank. The diagram does not show a relief valve in the rear tank.  If the front can not exceed 150 psi, then neither could the rear. Maybe I don't need another relief valve.

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Not sure were this should be noted. Pulled instrument mounting plate away from the dash to check on a couple of issues. I was surprised to see two 1/4" air lines from the front and rear air tanks connected to the back of the air gage. My gage has a red and green needle spinning on the same center post. These track each other very close. One of the air line diagrams I studied showed the front tank feeding the rear tank. I had "expected" that these would have a transducer at the tank and electrical gage. I now know that even with the ignition off, I am seeing actual air pressure in the tanks.

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  • 1 month later...

I now have about 2 hours under coach and with my arms into wheel wells spraying soap solution first and now windex (Cummins service center suggestion) on fittings. I found a very small leak at the dump solenoid where the fitting screws into the solenoid body. Pulled apart and teflon taped, no leak but coach still leaning overnight. I have sprayed the leveling valve down liberally with solution. There is a tube about 4" long that appears to be the exhaust. Filled tube but no bubbles. Sprayed the valve  area where the shaft goes into the body thinking maybe the seal is bad. no bubbles. I have leaned my arm against the flat bar that supports the valve from the bottom of the MH frame. the valve kind of groans maybe a bit of air flow. even spraying the hoses that are exposed in the wheel wells. Not having any luck with the leak. Any suggestions on where it might be?

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I have had "professionals" spend countless hours and my money on searching for air leaks and found none.

I fought a air leveling problem for years but finally decided to have Josam's go through the air leveling system in the rear and within a few hours found a few problems. Fixed them in the 6-Pack and wiring and I've been a happy camper since then.

As far as air leaks casing the two large air supply tanks to leak down, I no longer lose any sleep over it and it is what it is.

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Mike,

You've received some very good advice here, but I'm very disappointed that no-one has brought up a serious safety issue.

NEVER, EVER get under any vehicle that is supported by air suspension or hydraulic jacks.
Though unlikely, a failure in the air or hydraulic system can suddenly drop the coach to within a few inches of the ground. Likely not enough room for your skull.
Get a good set of heavy-duty jack stands, rated for the load, and use them EVERY TIME!

I always hate reading about the coach owner who thought he'd only be underneath for a minute, and that was the minute that an air line or valve failed. 😭

The only time I even reach under my coach without them, is when I'm placing or removing the stands.

Good luck fixing your leaks, just please do it safely.
 

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Air bleed down is always going a never ending problem in a system which uses insert tube fittings. Prior to insert fittings heavy duty vehicle air systems used steel braided hose and fittings which were rated for use in low pressure hydraulic systems. Typically leakproof for the life of the vehicle.  I installed a 12V air compressor so that I can maintain a user selectable air pressure in the suspension system and insure that the vehicle remains level when parked without the use of jacks and when necessary to assist the hydraulic leveling system when parked on soft surfaces. The 3rd time I spent several hours in the mud jacking and digging my hydraulic jack pads out of soft camp ground soil was the deciding factor for me.

One thought after I posted this comment. A trouble shooting technique which divides a problem in successive halves often succeeds. Perhaps a mystery air leak could be found if one divided his system in  half or quadrants with two or four $8.00 valves.

Edited by Gary Cole
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I have been systematically replacing the cheap slip fittings with DOT heavy duty truck compression threaded fittings. So far I have located 16 air leaks on the coach. I have final reached a point where the bags never drop. Air is still leaking from the tanks slowly somewhere. I know my air dryer leaks and that WABCO will be replaced with a much better unit made by Bendix. Air leaks are a almost never ending issue.  

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I run my coach up on 3 levels of 2x's to give me an extra 4.5" of height. With the air bags deflated. I have room under all but the hydraulic only leveling jacks.  I don't get under the jacks.

Wondering were you extend you jack stands up to to support the coach. Jack stands would have to be close to 2 foot tall to reach the frame. The steel supports for the trailing arms might carry the weight of the coach but standard jacks would not go under them.

In looking for leaks, I have tested with soap multiple times the following:

air fitting to hose and threaded fitting into top of air bag x 2 bags,

2 Tees screwed into a bulkhead fitting, hose coming from valve, hoses to front bag and rear bag, hose to dump solenoid. Tees swivel on their base and do not leak at the swivel. no leaks on threads screwed into bulkhead fitting.

dump solenoid fitting not leaking and not leaking thru the valve to exhaust port.

Passenger side does not loose air. only driver side. I am beginning to believe that the air may be leaking backwards thru the leveling valve as the tanks loose air pressure. My next test will be to drain air pressure in the tank immediately after shutting off the engine to see if the coach tilts as the pressure goes down. That might indicate the backwards flow thru the valve if it lowers. I had been assuming that the leak was in the bag air system. It may be from the supply/tank with back flow. 

 

Gary, I have thought about installing temporary valves to isolate into sections with a pressure gage to tell if leaking.

Rob, are you getting the better quality fittings online or local?

I found the leveling valve at $150. Asked the company if they had a repair kit.

 

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Mike,

I place the stands under the vertical supports that support the trailing arms, and under the front crossmember where the front hyd. jack mounts, directly under vertical supports.

I store my coach on the stands, so I can retract the jacks, protecting the rams from the elements.  I've never had any indication of distortion or flexing of the lift points.

 

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On 8/5/2021 at 5:46 AM, ok-rver said:

I know that getting the end of the tubing square when cutting without burrs.  Wondering if the PVC tubing cutters would be a good way to trim off a little to restab fittings?

Mike I use a PVC cutter. I also put a slight bevel on the tubing and use a lubricant such as dish soap such that it does not cut the O ring when I insert the tube. There are water based lubricants which are specifically designed for the process. I also make certain that I have a couple of inches of straight tubing coincident with the fitting plane and secure the tubing with ultraviolet resistant tie wraps. The process only takes a few minutes if one makes sure that he has everything he needs before he crawls under the coach. I've observed instrumentation technicians doing their work and they consider a leak of any kind a complete disgrace. RV manufacturers must have a somewhat different philosophy.

Edited by Gary Cole
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There is a difference between Ride Height Air Valves and Air Leveling Valves.

Sure would like to know exactly which system we are trying to fix for the OP.

Plus there are two different brands that were used on our coaches, HWH and Valid. One is made it the US and one is from Canada.

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9 hours ago, Gary Cole said:

Robert you are the man. I'm going to quit feeling sorry for myself , suck it up, and get to work.

 

 

Thank you sir. Most were leaks that needed a good amount of very soapy water solution. Most of the leaks were from the fittings and pressure valves on the tanks. Not one bag was leaking. Like many others I put together a series of 2 x 10 boards to make ramps. Drove the large unit up on the ramps so when the air bags dropped from taking off the lines my butt would not get squished. The air tank water drain valves were leaking front and rear. Good luck, take your time and enjoy the  beautiful underbelly of the these mechanical beast we drive around. They are complicated and simple at the same time. No wonder some guys name their coaches with the name of a woman.

Edited by Nevada Rob
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I have hydraulic jacks for stationary leveling of coach. The system I am troubleshooting is the ride height system to the suspension air bags. Will use ride height system in the future.

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On 8/5/2021 at 2:00 PM, Gary Cole said:

My winter project is going to be hydraulic rear lift for a motorcycle. 

Unless it’s a small bike you run the risk of overloading your rear 20K axle. What is your rear axle weight? Maybe start a new thread with your axle weights and bike weight.

Edited by Ivylog
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Dick I'm thinking along the lines of a dual purpose bike, street legal with off road capability.  Not something I would use to carry an 800lb bagger on. Just don't like the nuisance of towing an auto or trailer. 

With reference to other tales, I have never observed an RV being weighed with hopes of it being 1000 lbs overweight. I suspect they are more interested in rock haulers and other sort running 40,000 lbs overweight while dodging the scales.

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