Air Fails To Build Intermittently; Parking Brake?

[The HUlk]

He said he took the govenor apart. Could have changed the build and blow off threshold psi. He says it's dumping air fast when the brake is pushed.

 

[The HUlk]

It's correct to lose some pressure when you mash the pedal down

How many presses of the pedal should it normally take before your primary is below 90 and the air warning activates?

 

[gottaluvit]

Glad it didn't blow up!



Something is dumping alot of air when the brake pedal is depressed. I would start looking at the brake pedal and everywhere else for air leaking using the folowing method.

Fill a spray bottle with soapy water, grab flashlight and find a helper. Air up the truck to full pressure until it blows off. Turn off everything. It needs to be quiet enough to hear small air leaks well. Have soldier B press the brake pdeal as you move about the truck zeroing in on where the air is coming from. The spray bottle/flashlight tells you exactly where it's coming from. Check dash plumbing, in and out of the cab, frame rail plumbing, Brake area. Engine bay.

Thing is it only drops what seems like a normal amount with each press of the pedal (like the 18 wheeler I took my cdl class in). Its just that it dont start pumping air to get the pressure back up. I do need to eliminate the relay leak but cant see how the little bit it leaks has much to do with the air pressure going below threshold. The alcohol was methanol based air brake antifreeze for older systems with no dryer. I actually was concerned with the flammability but I was outside and it was raining. Thanks.

 

[gottaluvit]

There are check valves at each tank, I searched here and found a Bendix number that my local truck shop ordered for me. Their normal issue is either rust(wet tank) or getting broken on the trail.

Have you put a governer on it yet?

Not a new gov but took it apart and it looked nice inside (from what I could see). I am considering getting a new one though.

 

[gottaluvit]

He said he took the govenor apart. Could have changed the build and blow off threshold psi. He says it's dumping air fast when the brake is pushed.

It still cuts out at 130, where I last set it. Forgot to mention I bumped up a bit.

 

[gottaluvit]

How many presses of the pedal should it normally take before your primary is below 90 and the air warning activates?

If I remember right it should (and mine does) lose 5# +- per pedal press.

 

[Ford Mechanic]

How many presses of the pedal should it normally take before your primary is below 90 and the air warning activates?

I'll check,

You can't hear the compressor kick on when you have the problem?

 

[gottaluvit]

It's correct to lose some pressure when you mash the pedal down, then when holding pressure it should stabilize and not lose any more unless pressed harder.

This is what it does. Made me think treadle and chambers/diaphrams are good.

 

[gottaluvit]

There are check valves at each tank, I searched here and found a Bendix number that my local truck shop ordered for me. Their normal issue is either rust(wet tank) or getting broken on the trail.

Have you put a governer on it yet?

Crawling under as soon as I put this phone down to start tearing into them. Can I see/clean the rust/gunk?

 

[gottaluvit]

I'll check,

You can't hear the compressor kick on when you have the problem?

Heck, I cant tell over the noisy engine. Dont really hear a change like when its behaving properly.

 

[Ford Mechanic]

So with the truck aired up fully, one press to the floor drops the primary to 100 psi and the secondary to 110. Press #2 primary hits 85psi and secondary hits 100psi.

You do hear a rush of air when mashing put it should stop when holding.

 

[gottaluvit]

He said he took the govenor apart. Could have changed the build and blow off threshold psi. He says it's dumping air fast when the brake is pushed.

Theres really not much one can do inside. I just made sure all ports were clear. Went below that adjuster bolt by removing a snap ring but it was clean and oily(manufacturer's grease) under there.

 

[gottaluvit]

So with the truck aired up fully, one press to the floor drops the primary to 100 psi and the secondary to 110. Press #2 primary hits 85psi and secondary hits 100psi.

You do hear a rush of air when mashing put it should stop when holding.

Whoa. Yours drops 30 with one press then 15 more on second. I aint losing near that much, just not building once I do lose. Okay. Im firing this sand dune up and checking again. Right now. No rush of air and no loss on hold.

 

[Ford Mechanic]

I can hear mine just before it kicks off running down the road, same as in a couple other air brake vehicles I drive. Over 100 psi kinda sounds like a rod knock. As soon as it blows off it stops.

Mine seems to kick on around 100 psi at the primary tank.

 

[Ford Mechanic]

Whoa. Yours drops 30 with one press then 15 more on second. I aint losing near that much, just not building once I do lose. Okay. Im firing this sand dune up and checking again. Right now. No rush of air and no loss on hold.

That's with the pedal pressed the whole way down now, less than that will take less psi.

 

[Ford Mechanic]

My phones about dead, I'll check back in a hour or so

 

[gottaluvit]

I can hear mine just before it kicks off running down the road, same as in a couple other air brake vehicles I drive. Over 100 psi kinda sounds like a rod knock. As soon as it blows off it stops.

Mine seems to kick on around 100 psi at the primary tank.

Hmmm. Just aired from 60 to 90 in 55 seconds at 1100 rpm. Primary dropped from 120 to 109 and secondary didnt move on first pedal press with engine off. Second full press brought primary to 92 and secondary to 113. Third press 81 primary and 109 secondary. All presses were as if normal braking on a slight downgrade. Fourth press 72 primary, 108 secondary. On the fourth one I held for 30 seconds and gauges held steady with zero movement on the hold. Engine not running.

 

[gottaluvit]

I can hear mine just before it kicks off running down the road, same as in a couple other air brake vehicles I drive. Over 100 psi kinda sounds like a rod knock. As soon as it blows off it stops.

Mine seems to kick on around 100 psi at the primary tank.

I surely cant hear it going down the road. I have noticed it sounding like noisy engine when stopped right before it cuts out. By the way, thank you very much for going out of your way to help me. I really appreciate it as well as everyones help on this site. You'alls good folks!

 

[gottaluvit]

That's with the pedal pressed the whole way down now, less than that will take less psi.

Oh. I see. Didn't think of that.

 

[gottaluvit]

My phones about dead, I'll check back in a hour or so

No rush. I've been off and on working on this beast since I got it in mid April. Sitting is hard on any vehicle. Especially after so many private's fingers in it and then resting in Louisiana till GP moved it.