M920 Pusher Axle control problem

[jamboly]

Got my M920 last week. One of the first issues I need to resolve are the air leaks. I have two left unresolved. The first is the Saftey relief valve on the air drier. Anyone know a replacement part. The second issue is that I continually have air coming out of the lift/lower control valve. The valve has four threaded ports in it. Three have hoses hooked up. The port that is next to the gauge is blowing air. I am not sure if this is some sort of relief port and the valve is bad or if there is a plug missing. I have done a lot of looking for info on this valve and have come up with nothing.

 

[NDT]

If you search "air dryer" you will find a post by cornrichard where he has attached the Bendix manual for the air dryer. Very useful info. Not sure about your Granning controller, but I believe it should only be venting if you are moving the tag axle up or down. Most likely a bad O-ring in the control valve.

 

[jdgreen]

Not to hijack on a thread, but can someone tell me the wheelbase on a 920?

 

[Bighurt]

211 inches

 

[jamboly]

If you search "air dryer" you will find a post by cornrichard where he has attached the Bendix manual for the air dryer. Very useful info. Not sure about your Granning controller, but I believe it should only be venting if you are moving the tag axle up or down. Most likely a bad O-ring in the control valve.

I guess it helps in doing searches if you spell what you are looking for correctly. The air "dryer" manual helps point me in directions other than a leaking saftey valve. (Great reference. Glad he posted it) However, if anyone has a part number on the saftey valve, it looks like that would be the "easiest" thing to try first.
As far as the Granning controller, it vents all the time, in both positions. Is the O-ring easy to replace?

 

[reb87]

I had to put a new diaphram in my granning controller. I had a few others around to use but I think you could get one a truck parts place.

 

[jamboly]

The real problem I am having with the air coming out of the pusher axle control valve is that I can't figure out how it works from the control standpoint. I lookrd at how it is wired (hosed) up and it makes no sense to me (I get confuse with simple things). Everything is hooked up like the -20 manual shows, so I guess everything is hooked up right. The pusher axle goes up and down like it should. However, I can never get any pressure readings on the gauge (The gauge reading will go up a little when I turn the regulator up and put my finger over the hole in the valve that all the air is coming out of. The air only comes out when I put the valve in the down position, and continues to come out as long as there is air pressure. I don't understand how an O ring or diaphram could be causing this.

 

[R Racing]

Take the regulator valve appart . They only leak if there is dirt on the seat or if you have a cut O ring. A new Regulator is cheap ( less than $60.00 ) I hope this Helps !

Jim

 

[cornrichard]

I had the same trouble with my safety relief. I replaced it with an air compressor safety valve. You have to get one for a compressor that relieves at about 150 psi. I found one with the right threads and everything.

I did not know what the correct spelling for dryer was so I just went with the one Bendix used.

 

[M920]

The real problem I am having with the air coming out of the pusher axle control valve is that I can't figure out how it works from the control standpoint. I lookrd at how it is wired (hosed) up and it makes no sense to me (I get confuse with simple things). Everything is hooked up like the -20 manual shows, so I guess everything is hooked up right. The pusher axle goes up and down like it should. However, I can never get any pressure readings on the gauge (The gauge reading will go up a little when I turn the regulator up and put my finger over the hole in the valve that all the air is coming out of. The air only comes out when I put the valve in the down position, and continues to come out as long as there is air pressure. I don't understand how an O ring or diaphram could be causing this.

I had issues with the lift axle controls on my M920A1 for years.....seems every time I fixed one thing, another part gave me trouble.
I still have a brand new regulator valve, that I can send you if you need it, but I finally just ordered a complete lift axle control pannel from a company called "APSCO" in Tulsa OK. It is a complete pannel that is pre plumbed and all you need to do is hook up one supply line, one line to the lift bags and one line to the load bags...works sweet and I have not had any issues with it since then.

The APSCO part # for the whole pannel is: CON-3A

It is available through truck supply places like "Bruckner's Truck Centers".

PM me if you want to just try the regulator....

Soni

 

[jamboly]

Well I finally got around to pulling out the pressure regulator and up/down control valve for the pusher axle control. I carefully marked the hoses and fittings so I could get them back together the same way. Everything looked good in the control valve and there was a little junk in the pressure regulator, which I cleaned out. I put them back in, and same problem. I decided to take the control valve back out. There was still some pressure in system as I was disconnecting the lines. When I disconnected the line to the up position line (lower one), I had a bunch of air coming out of the line. That didn't make sense to me, so I took this line (one connected to up position fitting) and swapped it with the one at the back of the valve. Guess what. It works. Thanks to everyone that helped out on this. If I wasn't told to check out the inside of the valve and regulator, I wouldn't have stumbled on to the solution.