[Michael]

The K910026 = Norgren.com # K41EA00KAS1KA2, $66. It is a normally closed 3port/2 way spool valve. It is normally closed because there is a spring on one end that pushes the internal spool closing the pathway whenever pilot air is not present at the other end.

So problems could be:

a) internal corrosion to the spool and or body

b) o-rings are bad on the spool

c) or it’s still getting pilot air, not allowing the spool valve to close all the way, from a bad norgren up stream. This is a whole other can of worms

My suggestion is to pull up your bus air diagram on the Prevost website. Then you can see the air path. Next you might want to pull that valve apart and see what’s going on. You can buy a new one from Prevost, Norgren, or ebay.

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Mike Harper

2004 Marathon XLII

[al]

Don’t forget to consider moisture or water getting into the pneumatic system and a hydraulic lock occurring to prevent full travel of the spool.

The greatest enemy of our coach air systems is water and it makes a reasoned diagnosis of problems very difficult.

[Michael]

Don,

I will pull the diagrams tonight. I replaced that valve yesterday with a new one, hoping that was the issue, so I do not suspect it is the valve and it is much more likely your 3rd option – “it’s still getting pilot air, not allowing the spool valve to close all the way, from a bad norgren up stream. This is a whole other can of worms.”

When I get the diagram I try to figure out which valve drives the pilot and likely head that direction.

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Mike Harper

2004 Marathon XLII

[Archived]

Thanks Jon, I assume when a new valve is put in it would likely eliminate that issue.

Also, I was reading the leveling system diagnosis piece you did a while ago. Very helpful and thorough!!

Don, Jon:

The prevost site did not have a pneumatic for my model number or year (96 XL with a T-VIN), but I did find a detailed diagram for the XL 45 elsewhere. I attached the appropriate section for my valve in question that is letting air escape (far right in the diagram). It seems to me that the actuator port is 12 which is attached to the top of the Solenoid rack labeled air supply. Normal port 2 is open to port 1 and 3 is closed, but when actuated by port 12 it connects port 2 to port 3. I attached the diagram from the valve as well.

If you think I am right on the above, any ideas on diagnosing the Solenoid rack “leaking” when not actuated?

My first time taking on this system obviously.

Thanks as always!!

[Michael]

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Mike Harper

2004 Marathon XLII

[Archived]

That valve is the Norgren that exhausts air from the air bags when in manual mode and you are needing to deplete air.

Typically your 5 port Norgrens should be locking air in the air bags with the key off unless you have the older style system logic that requires accessory pressure. If your accessory air pressure is well above about 35 and you are leaking air I would guess a 5 port Norgen might be the culprit. Where and which way does the bus lean?

FWIW, as is typical with Norgren valves, if the pilot port is 12 as an example, that means when actuated it opens the path between valve ports 1 and 2. That might help with your diagnosis.

[Harry]

The bus isn’t really leaning. I lose aux air pressure pretty quickly which triggers the tag axle air release. I am trying to get the aux pressure to maintain which led me to hearing the air coming from the exhaust port of that valve when the bus is turned off.

[Mark]

The #1 top armature/coil on your 5-stack is the air supply to the pilot(12) of the K910026 spool valve that you replaced. When you turn the key off, the #1 armature/coil is de-energized and it is suppose to close not allowing any air to that #12 pilot on the K910026 spool valve. Take that line off at #12 pilot and see if air is flowing. If it is the armature is leaking.

“armature” = pt# 54462-31, $41 norgren.com

If you need coils?

12v coil = pt# 54452-02 = $25ea – https://www.norgren.com/us/en
24v coil = pt# 54452-03 = $18ea – https://www.norgren.com/us/en

[Dan]

New Information.

If the coach is not leaning and you hear air escaping until the tag axle pressure unloads you have the reverse logic system. But also based on your comment it sounds like the air that is escaping is less likely to be suspension related if the coach does not lean.

It could be anywhere in the accessory system.

[al]

Well, I was able to air it up and remove the line into the 12 on the valve and no air was present yet air continued to be exhausted from port 3.

Unless I am missing something that seems to clearly point at the valve as not closing completely. Hard to believe that a new valve would have the same issue as the one I removed?? Maybe next step is to order a new valve from Norgren and see if that resolves it.

[Art]

Agree Jon, although I can hear and feel the air coming from that valve which happens to be in the level system. That is why I asked if it was normal as I did not expect that to be the leak but it seems it is.

[Bob]

Don, Jon,

I was looking at it again this morning and I do think it is leaning to the front.

I am sorry if these are stupid questions, but I am trying to figure out if I should check something else that could be causing the air to leak out of that valve with the key off. I can look at the front control solenoid/valve on the rack given it is leaning to the front. I guess the good news is I know exactly where the air is leaking. The bad news is I still haven’t figured out what would cause it to leak there. I did order the new valve to try, but since this one is new I am thinking I am missing something else.

Thanks as always for your wisdom.

[Archived]

mike: I posted about my bus has covid; was referring to pilot valves and norgren valves doing strange /unusal new things. If you have old valve off and ends off see how easy spool /piston pushes. should be no drag. put a drop of air tool oil on it and check again for drag.. When new the spools were assembled with a little white grease to lubricate o rings against alum bore. I have seen that lube use it’s elastic effect when not excerised. Until your post I was ready to tear into the system again.. got me to thinking what could change a dramatic change.. Might even drop a drop or two in port to see if it loosens valve up/// not quart//// moisture is our biggest prob in air system because it developes a white powder corrosive reaction with the alum…If your norgren valve bore is clean and smooth –no scratches.. for action to be deminshied you can buy new oring kits for 12$ each. I hope this hasn’t been to rambling but also hopes it makes sense. these are all pretty straight forward and simple. Basically on or off -one direction of flow or other. I think that lubricant was luberplate.

[al]

Just wanted to post the conclusion.

After studying the valve schematics I realized that the valve in question is always open from port 2 to exhaust port 3 and the 12 (as Jon pointed out) opens port 1 to port 2, closing 2 to 3. I then saw that the 5 way valve above this valve controls the exhaust letting air go to port 2 when initiated. Therefore it pointed to that valve (K81EA00-KAC-KAC) the 5 port. I replaced that yesterday and the leaking has stopped out the below 3 way exhaust.

Now that it is fixed I noticed another leak in the drive solenoid armature so thanks to Don I ordered them and will replace that as soon as in from Norgren.

Learned a lot about this part of the level system and am on my way to fixing the leaks. Thanks!

[granvil]

thanks for updating!!