WRECKER AIR VALVE 936a2

[Kbussey]

I read everything I didn’t see anything about why hydraulics are slow… that valve behind the cab appears to set the brakes it goes into the floorboard to the brake pedal or to that spring brake override switch. Air leak is more than likely to do with that interlock cylinder which has been disabled now along with disabling the auto front wheel engagement air valve when shifting into low gear. I’ll figure it out but I don’t need the interlock cylinder nor do I need auto throttle nor auto brake since the parking brake is already set when I am parked.

 

[Mullaney]

I read everything I didn’t see anything about why hydraulics are slow… that valve behind the cab appears to set the brakes it goes into the floorboard to the brake pedal or to that spring brake override switch. Air leak is more than likely to do with that interlock cylinder which has been disabled now along with disabling the auto front wheel engagement air valve when shifting into low gear. I’ll figure it out but I don’t need the interlock cylinder nor do I need auto throttle nor auto brake since the parking brake is already set when I am parked.

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If you have an air leak, trying to find it with the truck running (to build air) is really difficult. With a separate compressor - house air or shop air - that you plug into the front of the truck will help. You plug the external air into the driver's side gladhand with another gladhand attached to your compressor.

I had a pin hole in the bottom of the air tank under the driver's step on my truck. I couldn't hear it. Couldn't feel it with my hand either. Never sprayed in the right spot with soapy water and a spray bottle - because I was expecting an air line leak.

With the truck off, it took just a few minutes to find the problem.

Maybe give that a try.

 

[simp5782]

I read everything I didn’t see anything about why hydraulics are slow… that valve behind the cab appears to set the brakes it goes into the floorboard to the brake pedal or to that spring brake override switch. Air leak is more than likely to do with that interlock cylinder which has been disabled now along with disabling the auto front wheel engagement air valve when shifting into low gear. I’ll figure it out but I don’t need the interlock cylinder nor do I need auto throttle nor auto brake since the parking brake is already set when I am parked.

It was designed that way in case of a linear valve failure. The valve on the parking brake that dumps the air. It would still apply the brakes for operation. Then they added the self recovery bypass. Too many redundancies really.

 

[Csm Davis]

I read everything I didn’t see anything about why hydraulics are slow… that valve behind the cab appears to set the brakes it goes into the floorboard to the brake pedal or to that spring brake override switch. Air leak is more than likely to do with that interlock cylinder which has been disabled now along with disabling the auto front wheel engagement air valve when shifting into low gear. I’ll figure it out but I don’t need the interlock cylinder nor do I need auto throttle nor auto brake since the parking brake is already set when I am parked.

The wreckers are really the only trucks that need the transfer case inter lock!

 

[KN6KXR]

I would be inclined to stick a gauge on the system and see what the static hydraulic pressure is. I have no idea what the spec is. I've chased my tail on systems because of a piece of junk stuck in a relief valve. Besides that it's good to have a test point for adjustments. If you do find a spec on the pressures please post them up, as I have a new to me M936A2, and I'll do likewise.

 

[simp5782]

I would be inclined to stick a gauge on the system and see what the static hydraulic pressure is. I have no idea what the spec is. I've chased my tail on systems because of a piece of junk stuck in a relief valve. Besides that it's good to have a test point for adjustments. If you do find a spec on the pressures please post them up, as I have a new to me M936A2, and I'll do likewise.

They are at 2200. Capable of 3200 but unless you swap all the hoses to fresh you will start blowing em