bogshotrods
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Sorry for the mistaken identity Artisan, I went ahead and down loaded ALL of the TM's and I'll keep em handy, I appreciate the help 
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M923 CTIS problem
- Thread starter Suprman
- Start date
Dawsongrant98
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Okay fellas. I have an odd situation that maybe someone can assist me with. Just unloaded a 1990 M936A2 Wrecker that was sent through the rebuild process at RR. It was finished in 2011 and driven 200 miles after. Here's the deal.
* Learned the light switch trick and that worked fine for seeing control panel lights.
* Read everything I could find through the TM link at the beginning of this post.
* Truck showed up with tires down to the runflats.
* Cleared the Control Panel like the TM suggested with the switch off.
* When I start the truck and the air builds up to 120 the Highway light goes on and off.
* Air starts filling all the tires and a very loud squealing noise comes from a valve somewhere.( I checked this very carefully with something against the tires to see them raise up ever so slightly.)
* Then when the gauge comes down to 80 pounds the CTIS changes to a slightly different squealing sound and the compressor builds air. But the tires drop down to their previous height. So no net gain.
* I tried manually airing all the tires which works but as soon as I start the truck the whole process starts again with the result of loosing tires pressure.
* I even tried to drive around the block at 2k rpm like the TM suggested but still lost pressure down to the runflats.
I left it in my building tonight with all tires full. The only way I could keep the air from leaving the tires while backing it in was to choose Run Flat. That seemed to shut any drainage off. Although I won't know for sure till I go back in the am.
Thoughts?
* Learned the light switch trick and that worked fine for seeing control panel lights.
* Read everything I could find through the TM link at the beginning of this post.
* Truck showed up with tires down to the runflats.
* Cleared the Control Panel like the TM suggested with the switch off.
* When I start the truck and the air builds up to 120 the Highway light goes on and off.
* Air starts filling all the tires and a very loud squealing noise comes from a valve somewhere.( I checked this very carefully with something against the tires to see them raise up ever so slightly.)
* Then when the gauge comes down to 80 pounds the CTIS changes to a slightly different squealing sound and the compressor builds air. But the tires drop down to their previous height. So no net gain.
* I tried manually airing all the tires which works but as soon as I start the truck the whole process starts again with the result of loosing tires pressure.
* I even tried to drive around the block at 2k rpm like the TM suggested but still lost pressure down to the runflats.
I left it in my building tonight with all tires full. The only way I could keep the air from leaving the tires while backing it in was to choose Run Flat. That seemed to shut any drainage off. Although I won't know for sure till I go back in the am.
Thoughts?
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Siren sound is a bad hub seal.
Alexsha
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If you air up the tires and disconnect the ctis controller before turning the truck on, do the tires stay inflated?
I would check the 3 quick release valves. 1 on each rear axle and 1 just under the hood hinge. Also check the air dryer for leaks.
I would check the 3 quick release valves. 1 on each rear axle and 1 just under the hood hinge. Also check the air dryer for leaks.
Alexsha
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Would a bad hub seal deflate all 6 tires?
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Air leak at hub causes lower than intended pressure at wheel valves. Holding them open and allowing air to dump instead of filling them.
Dawsongrant98
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Not sure if this detail narrows the search or not. I can inflate the front tires from the Schrader valve exposed through the mud shield. To inflate the rear tires I had to use the valve on the inside of the wheel. The one next to the wheel valve just vented somewhere on the other side of the wheel and tire. All four were that way. But when I tried to drive it around the front tires went down too. Unless I choose the Run Flat button which to me seemed to block the system from letting air out of the tires.
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- Stratford/Connecticut
There is an air release valve on each axle. The entire system is mechanical once air leaves the valve body cab floor. If the system sends low air pressure to hold each wheel valve open, it will vent out the axle release valves. If the system sends fill pressure and it is significantly reduced due to a bad hub seal or other leak, then the mechanical wheel valve can see low pressure and be unintentionally held open to dump air instead of filling. The siren sound is a telltale sign of bad hub seal. I have heard of the seal being improperly seated before. If you stick your finger in the rubber boot on the release valves one will usually have some grease in it. This is from axle grease blowing out because of the bad seal.
Dawsongrant98
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The tires have all maintained the pressures for several days now. As long as I don't allow the system to try and fill them it is fine. I'll have some time to check the valves in a few weeks. Buried with other (positive) projects right now!
Thanks
Thanks
Alexsha
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Positive projects are nice.
So the things you need to check:
Wheel valve
Wheel hub seals
Quick release valves (3, 1 for each axle)
Air lines
120psi going into the CTIS pneumatic controller. (If your water separator in the cab is in working order, I think you can check the pressure on the bottom of the cup)
Fun fun.
For me, I'm trying to track down a leak that causes the CTIS to cycle over and over. The tires don't deflate, but it doesn't see the 62~65psi it's expecting.
Dawsongrant98
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Hah!
Now I'm in for some fun. We're polishing the concrete floor where I keep this beast so I decided to drive it to my house 5 miles away. Everything was fine till I noticed the air gauge dropping and not building back up! I made it home before running out of pressure thankfully. Upon parking the truck I hear the air dryer ( I think it is the air dryer) exhausting air out the bottom. It is located on the outside passenger side frame rail behind the fuel tank. Has a filter on the top and remember, this is a wrecker. Do you suppose this is more CTIS ecu stuff? How does the dryer work? An electrical charge opens the valve after receiving a signal from the controller? Or do you think it is just stuck open? I was thinking about removing the wire to see if it would shut.
Thoughts?
Now I'm in for some fun. We're polishing the concrete floor where I keep this beast so I decided to drive it to my house 5 miles away. Everything was fine till I noticed the air gauge dropping and not building back up! I made it home before running out of pressure thankfully. Upon parking the truck I hear the air dryer ( I think it is the air dryer) exhausting air out the bottom. It is located on the outside passenger side frame rail behind the fuel tank. Has a filter on the top and remember, this is a wrecker. Do you suppose this is more CTIS ecu stuff? How does the dryer work? An electrical charge opens the valve after receiving a signal from the controller? Or do you think it is just stuck open? I was thinking about removing the wire to see if it would shut.
Thoughts?
Alexsha
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If the air dryer is venting down, then there's a valve there that can get stuck open. I think you just need to WD-40 it (that's a verb now!) and get it closing. Might be a good idea to service (replace) your air dryer. You can take it off, clean it, replace all the filters/cartridges, etc for $150 or so... or buy a whole new upgraded air dryer for about $100 + shipping from people on this forum.
Also, I just noticed, but the rules here say you have to include at least your state in your profile. You probably want to update that.
Also, I just noticed, but the rules here say you have to include at least your state in your profile. You probably want to update that.
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The purge valve on the bottom of the dryer is operated by air. A signal air line from the governor tells it when to purge. The wire you see if for the heater.
You can push it closed through the hole in the bottom. Feel for the bolt and push up. You will likely have to do this every time it purges though.
You can disassemble and clean the purge valve to get you by but the dryer needs to be serviced completely. See my post in this thread:
http://www.steelsoldiers.com/showthread.php?135608-M925-air-brakes
You can push it closed through the hole in the bottom. Feel for the bolt and push up. You will likely have to do this every time it purges though.
You can disassemble and clean the purge valve to get you by but the dryer needs to be serviced completely. See my post in this thread:
http://www.steelsoldiers.com/showthread.php?135608-M925-air-brakes
Dawsongrant98
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Yeah, I was afraid of that.
Fixed my profile and noted a few of our toys. Don't get the wrong idea about us. I'm just an old farm boy from Iowa who drove a truck for his Dad! Couldn't rub two nickels together for the first 32 years!
Fixed my profile and noted a few of our toys. Don't get the wrong idea about us. I'm just an old farm boy from Iowa who drove a truck for his Dad! Couldn't rub two nickels together for the first 32 years!
Dawsongrant98
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That worked great. Pulled the plunger out, cleaned it and the barrel out and lubed them up and they're fine now. Drove the truck 10 miles, no issue. I did remove the cover off of one wheel valve and you'll never guess what I found! The spring, tin cap, and rubber diaphragm were in backwards! I didn't have time to check the others yet. I can't imagine Red River did that. Anyway, I'm planning to go through each component that way and I'll bet the system will work fine. All the fasteners are like brand new and everything comes apart really easy.
Thanks again for all the insight gentlemen!
Alexsha
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Okay... I'm not doubting you, but I have to double check what you're saying. This is how they SHOULD be:
In what way were they backwards? Was the diaphragm not "nipple" up? Was the spring directly on the diaphragm instead of in the cup?
Dawsongrant98
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Okay, with the larger piece laying flat, as I lifted the cover off, the first piece was the rubber diaphragm with the nipple towards the cover, then the tin cap, then the spring between the cap and the base! Basically, the spring was pressing on the wrong side of the diaphragm.
Now, here is a long story that is just for entertainment. With the caveat that it may not be that entertaining! So read at your own risk of having wasted 5 minutes and being bored.
For the last four days I had the TM "parts exploded view" opened on my computer of the wheel valve on a separate tab. I typically have 10-20 tabs open on my screen at any given time. On a regular basis I review them and close the ones I no longer need. Kind of using them as a reminder to do things or follow up on a project. I bet I looked at that wheel valve exploded view 200 times over the last 4 days. Yesterday morning I finally decided I didn't need that open on my computer any more. I hadn't planned on driving the truck for a month or so but you know how plans change.
I thought I would be able to rent some space near where we are polishing the floors in our warehouse but to no avail. I now (as previously stated) needed to drive the truck to one of our other buildings 5 miles away. So the other thing I must admit is that I no longer have my CDL license. And the the truck had the license plate in the front window instead of the rear where it belongs. No front plate required in Florida. The truck needed fuel so I stopped at a gas station to fill her up and right as I stopped next to the pump, two motorcycle Highway Patrol Officers (not local police or Sheriffs ) roared right by me. That actually freaked me out a bit they came so close! This so reminded me of my youth driving a 1971 Kenworth W900 and a Talbert RGN lowboy with some not particularly noticeable violation at any given time and encountering the MAN! Things like, being over weight on the rear axles, not have a proper fuel permit, license expired on the truck, over on my logbook hours, being 14 years old by myself only carrying a School Permit! You know, little things.
So, with that encounter out of my way I relaxed a bit and began the process of fueling the truck. About 2 minutes into fueling, guess who pulls up immediately behind me? Like 5 feet from the hook block hanging on the back of my wrecker boom! You got it, a Florida Highway Patrolman in a cruiser. Oh Crap! No plate on the back of the truck and no CDL! So what else can I do but engage the guy with small talk. He makes a few comments about the cost to fill the truck up vs his car, I ask about the longevity of the new patrol cars and solicit his opinion. All the while I reduce the flow of fuel into my truck to the slowest speed, the very first notch on the pump handle! Ahhhh, He finishes well before I do and wishes me a good day, then pulls away from the pump and I give him a nod and wave. Finally, crisis avoided.
Not so fast mister!! As I finish and climb up into the cab, and to my surprise, guess where the officer went? Really? He's parked now right in front of my truck at the curb where the entrance to the convenience store is. And he is sitting in his car! Now what? I sent my wife this text and asked her to say a prayer!
So I climbed back down and decided to waste some time going to the bathroom. I came out and he was still there. Now I'm paranoid he has figured this all out and is just waiting for me to pull out onto the highway and nail me! People are walking around the truck, kids are coming over to look at it, you know the drill. So I decide to go ahead and leave. Whatever happens was meant to be. As I am pulling out of the station driveway onto the main highway my wife calls me. "Have you left yet?" I of course presume she is talking about the sticky situation I am in currently. Nah, she wants me to bring home a vacuum from our warehouse. So I give her the blow by blow up to that point just as you understand it so far from this gibberish. A mile down the road and I see no officer or patrol car, relief, looks like I'm in the clear. Now if I can just get to my other building and park this sucker!
Hold the phone Nurse Jackie!! I'm still on the phone with my wife, 2 miles from my destination and now I have a new emergency. The "Low Air" light just popped on. I check the gauge and it is reading 40 pounds! And dropping. I shift to a lower gear to bring the revs up hoping that will compensate for whatever is leaking, but to no avail. Well, if you have been following this thread you all know what is going on. The air dryer has a stuck plunger and is venting all the while I am driving. All I can think of now is that the system is going to bleed down far enough that the brakes will lock up right there in the middle of US Highway XXX, 5:00 pm traffic!!! So I am freaking out a bit and tell me wife, (now remember, she just got the blow by blow story about my recent encounters and a little extra about how uncomfortable I am driving at the moment) "I have an emergency, gotta go!" No good bye, no details on why I cut her off. I find out a bit later that I could have shared just a few more details which would have provided a better domestic relationship experience for me later! Note to self, give details next time before hanging up. Hey, I'm 34 years at this relationship stuff. I can still learn a few things!
So as I wait for the truck to either overheat the drums, lock-up in the middle of the road, or get pulled over by my friend, ( I figure with the luck I am having he has to be somewhere around) I decided to drive another half mile to my house where I could work on this new issue. And as you might have guessed, I MADE IT!
Once home, I asked you all about the air dryer and with your help got that fixed. THANK YOU! I then was in the mood and decided to tackle the wheel valves or at least one. So I take apart the first one and it just doesn't look right to me. Can't make sense that the parts are in that order. Eureka! I'll just go look at the exploded view on my computer that has been open for the last four days! Ahh, "insert mild expletive" ( I rarely swear) I closed that tab earlier in the day. It's no longer open on my computer.
GOOD GRIEF!
IT TOOK ME THIRTY MINUTES TO FIND THAT STUPID PAGE AGAIN IN THE TMs!!!
Thanks everyone. And If that wasn't worth the read I offer my humble apologies.
Now, here is a long story that is just for entertainment. With the caveat that it may not be that entertaining! So read at your own risk of having wasted 5 minutes and being bored.
For the last four days I had the TM "parts exploded view" opened on my computer of the wheel valve on a separate tab. I typically have 10-20 tabs open on my screen at any given time. On a regular basis I review them and close the ones I no longer need. Kind of using them as a reminder to do things or follow up on a project. I bet I looked at that wheel valve exploded view 200 times over the last 4 days. Yesterday morning I finally decided I didn't need that open on my computer any more. I hadn't planned on driving the truck for a month or so but you know how plans change.
I thought I would be able to rent some space near where we are polishing the floors in our warehouse but to no avail. I now (as previously stated) needed to drive the truck to one of our other buildings 5 miles away. So the other thing I must admit is that I no longer have my CDL license. And the the truck had the license plate in the front window instead of the rear where it belongs. No front plate required in Florida. The truck needed fuel so I stopped at a gas station to fill her up and right as I stopped next to the pump, two motorcycle Highway Patrol Officers (not local police or Sheriffs ) roared right by me. That actually freaked me out a bit they came so close! This so reminded me of my youth driving a 1971 Kenworth W900 and a Talbert RGN lowboy with some not particularly noticeable violation at any given time and encountering the MAN! Things like, being over weight on the rear axles, not have a proper fuel permit, license expired on the truck, over on my logbook hours, being 14 years old by myself only carrying a School Permit! You know, little things.
So, with that encounter out of my way I relaxed a bit and began the process of fueling the truck. About 2 minutes into fueling, guess who pulls up immediately behind me? Like 5 feet from the hook block hanging on the back of my wrecker boom! You got it, a Florida Highway Patrolman in a cruiser. Oh Crap! No plate on the back of the truck and no CDL! So what else can I do but engage the guy with small talk. He makes a few comments about the cost to fill the truck up vs his car, I ask about the longevity of the new patrol cars and solicit his opinion. All the while I reduce the flow of fuel into my truck to the slowest speed, the very first notch on the pump handle! Ahhhh, He finishes well before I do and wishes me a good day, then pulls away from the pump and I give him a nod and wave. Finally, crisis avoided.
Not so fast mister!! As I finish and climb up into the cab, and to my surprise, guess where the officer went? Really? He's parked now right in front of my truck at the curb where the entrance to the convenience store is. And he is sitting in his car! Now what? I sent my wife this text and asked her to say a prayer!
So I climbed back down and decided to waste some time going to the bathroom. I came out and he was still there. Now I'm paranoid he has figured this all out and is just waiting for me to pull out onto the highway and nail me! People are walking around the truck, kids are coming over to look at it, you know the drill. So I decide to go ahead and leave. Whatever happens was meant to be. As I am pulling out of the station driveway onto the main highway my wife calls me. "Have you left yet?" I of course presume she is talking about the sticky situation I am in currently. Nah, she wants me to bring home a vacuum from our warehouse. So I give her the blow by blow up to that point just as you understand it so far from this gibberish. A mile down the road and I see no officer or patrol car, relief, looks like I'm in the clear. Now if I can just get to my other building and park this sucker!
Hold the phone Nurse Jackie!! I'm still on the phone with my wife, 2 miles from my destination and now I have a new emergency. The "Low Air" light just popped on. I check the gauge and it is reading 40 pounds! And dropping. I shift to a lower gear to bring the revs up hoping that will compensate for whatever is leaking, but to no avail. Well, if you have been following this thread you all know what is going on. The air dryer has a stuck plunger and is venting all the while I am driving. All I can think of now is that the system is going to bleed down far enough that the brakes will lock up right there in the middle of US Highway XXX, 5:00 pm traffic!!! So I am freaking out a bit and tell me wife, (now remember, she just got the blow by blow story about my recent encounters and a little extra about how uncomfortable I am driving at the moment) "I have an emergency, gotta go!" No good bye, no details on why I cut her off. I find out a bit later that I could have shared just a few more details which would have provided a better domestic relationship experience for me later! Note to self, give details next time before hanging up. Hey, I'm 34 years at this relationship stuff. I can still learn a few things!
So as I wait for the truck to either overheat the drums, lock-up in the middle of the road, or get pulled over by my friend, ( I figure with the luck I am having he has to be somewhere around) I decided to drive another half mile to my house where I could work on this new issue. And as you might have guessed, I MADE IT!
Once home, I asked you all about the air dryer and with your help got that fixed. THANK YOU! I then was in the mood and decided to tackle the wheel valves or at least one. So I take apart the first one and it just doesn't look right to me. Can't make sense that the parts are in that order. Eureka! I'll just go look at the exploded view on my computer that has been open for the last four days! Ahh, "insert mild expletive" ( I rarely swear) I closed that tab earlier in the day. It's no longer open on my computer.
GOOD GRIEF!
IT TOOK ME THIRTY MINUTES TO FIND THAT STUPID PAGE AGAIN IN THE TMs!!!
Thanks everyone. And If that wasn't worth the read I offer my humble apologies.
A real man is the kind of man that when your feet hit the floor each morning the devil says Oh Crap, he's up! 
- 1,450
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- 63
- Location
- Gray, GA
I enjoyed the read but I seem to be able to find humor in others troubles, same as my own. Glad everything worked out.
You ought to get your legals in order so you can enjoy the truck instead of looking over your shoulder. You should be able to ride by the "Po-Po" with a wave and a smile.
Now, about that Countach in your signature and some pictures...
I'll PM my email address so as not to clog the thread.
You ought to get your legals in order so you can enjoy the truck instead of looking over your shoulder. You should be able to ride by the "Po-Po" with a wave and a smile.
Now, about that Countach in your signature and some pictures...
I'll PM my email address so as not to clog the thread.