service brake operation

[doc76016]

Please excuse me if this is a completely naive question. I have only become reacquainted with the M35's after nearly 40 years and if I ever knew this I have long ago forgotten it. I have also searched the forums and read through the TM's without success. My question is this...

How is the service line supposed to operate? I _think_ it is supposed to send a burst of air to the trailer when the brake pedal is depressed. Is that correct?

If so, then could I remove the gladhand "cap" and open the stopcock and then depress the brake pedal to see if air is delivered at that point and then stops when the brake pedal is released to assure proper operation?

Also, if the M35 brakes started dragging after, say 60 miles, while not pulling a trailer and I then removed the "cap" and opened the stopcock and got a great expulsion of air, could I then assume that the air/hydraulic valve is faulty?


TIA,
mdh

 

[ida34]

Your assumptions are correct. The service air valve does provide air to the trailer when the brake pedal is pressed. If you had a build up that would not release then you should rebuild the airpack assembly.

 

[wsucougarx]

Ok another question, I have a glad hand air hose to air up the tires. I have not used it yet as I didnt know which side to plug the hose into. Which one is it? The SERVICE or EMERGENCY one on the back of the truck?

 

[jasonjc]

Emergency it has air all the time.

 

[wsucougarx]

Thank you Jason

 

[ida34]

On trailers with both connections the emergency side fills an air tank on the trailer. There is a relay valve on the trailer that allows the emergency supply from the truck to fill the tank. If the relay valve does not have pressure from the emergency line then it applies the brakes using the air in the trailer air tank. If is a break away type of device and it also will provide braking for the trailer if the truck looses air. This is why you use the emergency side for the air chuck. It is basically a direct line to the air tanks.

 

[doc76016]

Re: RE: service brake operation

Your assumptions are correct. The service air valve does provide air to the trailer when the brake pedal is pressed. If you had a build up that would not release then you should rebuild the airpack assembly.

Thanks for the kind reply. I believe that is the problem with my new M35a2. I'll report back when I finally get it repaired.

mdh

 

[ida34]

RE: Re: RE: service brake operation

There is a port that you can shoot some air tool oil in to keep things free. It is at the back and is a square head plug. I tool for opening water spigots works great. I think it is 1/4 inch. Do a search. Someone has posted pics of what to look for with instructions. It may help but I would suspect you are to far along for quick solutions but it may be worth a try.

 

[ida34]

RE: Re: RE: service brake operation

Check this out. Lots of info for you with pics.

http://www.steelsoldiers.com/index....r=asc&highlight=air+tool+oil+airpack&start=20