CTIS Weak Blow OFF On Deflate

[plainside]

HI,

M925A2. Here is what is happening, when the ctis cycles on first time start up it blows out the quick exhaust valves as it should (nice and loud) but when you drive it a bit the blow offs get very weak on the CTIS Quick release valves when the system does the normal 15 min cycle. (it barely hisses out) and being it can not blow off properly 4 or 5 light codes blinks on the ctis control module. I know there is an air pilot that runs the quick exhaust valves (all 3 of them). Happens the same way going from hwy to XC mode. Have the schematic but seeing if someone else has had the same issue. It is more of a hiss of air instead of a HOOONNNNKKK sound like it should be. something is not shifting properly. it is cold out but still should work you would think. 10 degrees.

Replaced the air dryer just because it should be done with these trucks with the same result.

 

[10Lugger]

Tread lightly. I noticed the similar symptoms in our 1078. CTIS was cycling and I took it out at about 12 degrees. It was about 1 mile from the shop and it cut loose. Gear oil shot out of diff seal like a exploding water balloon, the guy behind me said. At that moment CTIS did an all flash. Pulled over to see my nice fresh coating of stinky gear oil all over the underside. Did a lot of searching about the CTIS and read how care was taken, in the design for that not to happen, but I have pics of the let loose site.

 

[plainside]

Thanks for the post. Not sure exactly what you are talking about here but it does not sound good. This has happened several times before. CTIS air must be getting in the diff somehow. But what you are talking about sounds like just one axle. All the axle quick release valves are not functioning properly but do at times, so not sure if the pilot line is not function right or what?

 

[10Lugger]

I believe it relates to the cold. Ours did the all flash one other time (the day we got it). Drove it the same distance to a friends shop in 17 degree weather. It was cycling...then all flashed, dropped the pressure in the front tires, then filled back up. It was fine for the next 45 days or so. I suspect moisture or extreme cold affecting control. I did let truck warm up for about 10 minutes.

 

[plainside]

Your was blowing off weak? That is the issue here, the CTIS works perfect, it is just not blowing off at the end of the cycle properly on all 3 blow off valves under the truck. Something froze up I would think, but have used it in colder weather a few weeks ago with no issues.

 

[10Lugger]

[FONT=&quot]Yes, blow off was weak (according to your Honking Sound at blow off) I have no comparable to go by. Good luck? [/FONT]