I've got a 198? F? with a 8.2 Detroit that has air brakes of course with a weird problem.

When you crank up & build air pressure & try to release the brakes it loses it's pressure & the air seems to be leaking from a screw with a rubber washer on the pedal control.

You can access this screw from under the hood via a factory hole in the firewall.

It had done this same thing before & we just stacked another washer on it & it fixed it for a year

Now it sits outside my shop door with a axle broke because of this.

Number Dummy I'll go ahead & post the VIN so I can find more out about this truck Thank you

KB4NVJA58xx

 

11 digit VIN is 1980 and earlier related, but the 2nd digit is a number.

 

I would replace the treadle valve .You could also have a maxi can leaking and back feeding the system.
To check unhook air lines going to the brakes from treadle valve and plug valve to see if it still leaks. If so replace valve.

 

Bendix use to have a lot of good information on their web site about air brake valves. There may be some good information there for you. From what you describe I think you have a bad relay valve. If you elect to change the treadle valve be very careful about marking the lines and not switching them. Switched lines can defeat the back up circuit and leave you with no brakes if you loose a circuit.

B

 

Thanks OldB & HDTail I just pulled the rest of the broken axle out a few minutes ago & I'm going after the brakes now