Air brake questions

Alright, here we go. I KNOW all the questions I have can be answered by a TM, but I'm waiting for one to come in the mail, so here goes.

Got the new belt on, and it's pressurizing the system. I know this because I can hear a hissing and a "noise" coming from under the dash. Also, drained the port and starboard air tanks, as well as the air brake booster. Bled all my brakes. A mechanical air pressure gauge is in the works, so that's coming. Now, that "noise" under the dash, is that a 'low air warning buzzer'? How long should that generally take to turn off? Also, should there ALWAYS be air leaking from that little valve? From wherre the main air line comes thru the firewall, there's a jumper air hose going to this distribution block that has the chime in the middle, and a wire coming out the top and bottom. Is this where the air usually pops off when there's too much air pressure in the tank?

hissing noise

get a spray bottle ,mix uo some soapy water spray it on any where the airlines have a connection,hissing under the dash may be the WIPER CONTROL KNOB,leaking ,these things leak air terribly,thats why my post about electric wipers,horror story,onthe way home with my newly purchased m211,the rubber air line that connects the steel air lines from the wiper control up thru the dash at windshield lower left hand corner,then to the wiper units ,blew off, resulting in loss of power brakes,and air pressure,stopped truck ,crimped steel line with pliers and continued home,just spray soapy water on everything and watch for bubbles,good luck on your project

RE: hissing noise

MO-mudder, thats funny. My deuce did that same thing. In fact if you have it runnung and get under the dash, the valve with the two electrical connections coming from it, you will see a small hole on the right side(passenger). If you put your finger over it and air is coming out then the low air pressure warning switch is toast. Mine let go two weeks ago. Luckily one of the steel soldier members had one. Now just to get around to putting it on

Greg Jackson

Those are some good things to check...

Just to clarify a few things for you:

-The pressure relief valve is down by where the main air line connects to the tanks, it has a pull-ring on it's spindle so you can check to make sure it is not stuck shut. The air governor is on the firewall in the engine compartment. So, there should be no air leaking out from under the dash... either the wiper control or pressure switch for the low air buzzer is leaking, or the air accessory valve is open, (on the inside firewall above the passenger's feet), or you have a cracked hose or broken metal air line.

-I've never timed it exactly, but with empty air tanks, once I start the engine it takes around 2 minutes for the buzzer to shut off and the compressor unloads when the tanks are full in less than 5 minutes... Just enough time to walk around the truck, remove the wheel chocks and do a quick pre-trip inspection.

Regards,
Jon

Alright, just got in from the shop, and have made a couple corrections.
*Low air buzzer is shot
*Pressure relief on firewall is non-functional
*Electrical connection on top of distribution block was the secondary air loss, next to the buzzer
I bought a pressure gauge (like you'd see on an air compressor) and installed that on the line that WAS feeding the distribution block. I'll have to pick up a 2" gauge from someplace that'll fit in my dash panel, as well as some kind of pressure relief mechanism. I'll check with the KW dealership and see what that'll run me. I'll also figure out some way to get the horn working, also. My airpak is functional, cuz I also put a gauge where the plug was (on the airpak) and hit the brakes, and the needle jumped. I was thinkin about running a line from the airpak to the cab to another gauge so that I'd have a brake pressure gauge, too, just so I'd know if my brakes were ever failing. I did find the manual pressure relief; mine was on top of the driver-side tank.

I'm guessing that the relief valve on the firewall is shot, because I let it run for probably too long, and never heard anything blow off. What pressure is the blow-off valve supposed to trip at? Keep in mind, this is an M135, not an M35.

Oops!... I didn't realize we were talking about an M135. I know nothing about them, mine's an M35.

No problem. A lot of stuff interchanges. What PSI does the M35 trip at? I could always just hunt one of those down.

Midland air compressor m135

I have a 1952 m135 that is set up with a midland cristensen air compressor. The cristensen compressor is no longer pumping air so I have a replacement compressor from midland air brake company. It is water cooled like the old one but the inlet, outlet ports are not marked. Dose any one have any tm's on this compressor or pictures?

The Pop-off should be about 150#. There is also a rubber hose that goes through the firewall, about in the center, but behind the air cleaner (its hard to see), that can leak and its hard to find. Once you have the leaks solved, one air pressure gauge - the one in the dash cluster, will be adequate. JDT's description of the "air-up", is good for the 211/135 too. If you have a lot of leaks & trying to find them, sometimes its easier (and quieter), if you tap in the shop compressor for the air supply. Then you don't have to run the truck all the time, and you can hear the leaks. Its really worth while to take the time and solve the air leak problem. There should be a low air buzzer that comes on at 60 PSI. It should be real loud too. It can be replaced with a late model one. DOT likes it to come on at EXACTLY 60 PSI too! If it doesn't, that will get you a ticket faster then anything else I can think of.

Lowgear - put it on and run it - then hold your thumb over each port and you will be able to tell, which is which.

Thanks, I have disconnected the air in and outlet on the old compressor and it is DOA. as for the new one the oil ports are also not marked.