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View Full Version : Leveling Valves Science Project for the Luxury Newell Coach


Richard and Rhonda
12-22-2008, 08:20 PM
You guys will have to forgive me for being such an OCD engineer. It bugs me that the leveling valves seem to be a chronic problem, and there is not a good way to diagnose which one is giving you the problem.

So, I made a little jig to test the valves with. It was pretty simple, although the threads on the valves are 1/2-20 that is really close to 1/4 NPT, so I cheated and used a 1/4 NPT pipe coupling. On the side that mates to the valve, I used a brass washer robbed from an old valve, and used epoxy to seal the 1/4 NPT coupling to the washer. I drilled a hole in the washer to simulate the setup on the manifold distribution block in the coach. so to use the jig I applied air through a regulator, and put a soap bubble over the hole in the washer. I increased the air pressure using the regulator until I saw a bubble form. I called that the leak pressure.



I conducted a little experiment with the help of another. I was sent two old KIP valves that he had, I had two old AV brand valves, and two brand new HWH valves I just bought. My goal was to determine the cause of the chronic failures.

I disassembled all three sets and took some measurements of the springs and valve seats. I also used the jig to determine the pressure at which the valves started to leak by. To be more accurate, I should have used a 12 VDC source and cycled the valves a few times. Maybe next time.

Here are the data:
New/Used Brand Spring Ht Durometer Leak Pressure
New HWH (AV) 0.52 47 100+
New HWH (AV) 0.54 50 100+
Used AV 0.47 49 55
Used Kipp 0.54 35 10
Used Kipp 0.56 34 10

AV Urethane seat 100+
Reworked seat, lapped 70
New valve old seat 70
Old valve, new seat 100+

The experiment seems to indicate that significant deterioration in performance. No wonder we can't keep air in the bus. You can also see that the hardness of the seat, and spring height does not explain the change in leakage. I concluded it had to be degradation of the contact between the valve seat and the valve body.

I had made a new seat for one of the old valves out of same castable urethane I had in the office. First indication is that something like that may work to refurbish the valves, since that reworked valve did achieve near new leak rates. I do not know how long that material would hold up under use

I also tried lapping the valve and valve seat together using finger pressure and a light lapping compound (tootpaste). The lapping raised the leak pressure 15 pounds but did not fix the leak.

I also swapped an used seat into a new body, and a new seat into an old body to determine if the leak was seat or body related. One single data point indicates it's the seat.

It makes sense that the seat would be degraded by air blowing past it. The valve body is brass and the seat seems to be some moderately hard polymer. That was my intial thoughts anyway, but I had to prove it to myself before going to the next step.

I had two goals. One to make a device to be able to test the valves easily. Mission accomplished. Total cost about two dollars. The second was to ultimately be able to recondition the valves to seal in an easy and inexpensive manner. I will have to get some different urethanes to try now. I'll report back later on what I find.

Of course if the valve is not opening, that's a different problem, and requires a new coil. But generally people complain about them leaking.

Guys, don't throw the old ones away, there may be help on the horizon.

Jack Fouts
12-22-2008, 08:44 PM
Great information, thanks I'll put it use.

Richard and Rhonda
12-22-2008, 09:06 PM
Sorry the table is so hard to read. It doesn't look jammed together on the original submission or an edit option.

Neweller
12-22-2008, 10:28 PM
This is very good information Richard and the forum appreciates your effort for sharing this experiment with us. I have worked my fare share of air systems but you taught me quite a bit. Thank you.

fulltiming
12-22-2008, 10:54 PM
Great work Richard!!

As to the readability of the table, let's see if this works better using the code feature

New/Used Brand Spring Ht Durometer Leak Pressure
New HWH (AV) 0.52 47 100+
New HWH (AV) 0.54 50 100+
Used AV 0.47 49 55
Used Kipp 0.54 35 10
Used Kipp 0.56 34 10

AV Urethane seat 100+
Reworked seat, lapped 70
New valve old seat 70
Old valve, new seat 100+

HoosierDaddy
12-22-2008, 11:56 PM
I've been experimenting by installing a plain ol' home made rubber seal in the HWH valve. I've got them rebuilt and intended to just install them and see how they perform. Too cold to work on it now!!!! My coach is 40 miles away in heated storage. -3degrees last night...high of 15 today! I should make a handy tester like you did. Good idea Richard!
Merry Christmas!
Dean

tuga
12-23-2008, 01:21 AM
Great work Richard. My coach has the leans when I use the automatic leveling feature: press the AIR button twice. But if I raise the coach using the 4 arrows up button from road level it will not lean. Go figure!

Richard and Rhonda
12-29-2008, 02:39 AM
Just wanted to update you on the little jig I made. I used it today to test all 12 leveling valves on the coach. Four would not hold 100 lbs pressure without leaking.

It took about 1.5 hours to test them all. I marked the solenoid coils on all with the correct position, and then I unscrewed the nut that holds the coil on. I did that instead of unhooking the wiring. After that it's a quick job to unscrew the valve body and screw them onto the jig. Since I knew the new ones will hold at 100 lbs, I set the regulator on my air compressor at a 100 and just popped the jig on and off with a quick disconnect.

I had two new ones, so I had to try something on the other two that were leaking. I stole the idea of putting in a piece of material from HoosierDaddy. I used a pick to dig out the old seal material and used a piece of hard rubber to replace what I dug out. Actually I cut up a squegee that I had in the shop. It was the right thickness, and seemed about the right hardness. I used a little silicone adhesive to seal it in the cavity. I tested the "fixed" valves and they held 100 psi, so I put them in. We'll see how they hold up with time. I know which ones they are so they'll be easy to check.

I have been looking at the old valves with a microscope to see what was going on. All of the failed ones have microscopic cracks around the sealing area. The new ones are perfectly smooth.

If the fix holds up over time, then it will be an incredibly inexpensive solution compared to replacing valves at 80 per shot and hoping you got the right one.

On yeh, one more thing the valves that were bad must have been the ones that came with the coach, there was a 04 93 code on the valve body.

Richard and Rhonda
12-29-2008, 02:42 AM
Tuga,

It sounds like the device that tells the automatic system is not level. It is easily adjustable, you just have to find it. Look under the control pad first, it is about 3 inches in diameter, and has three adjustment screws to fine tune it.

fulltiming
12-29-2008, 02:58 AM
On my coach, the level is up under the floor in the center of the coach in the bay directly behind the mid-entry door so the location can be quite varied.