Primary Braking Failure

[Derka]

04 Thomas Saf-T liner C7.


No problems driving/operating. Parked it for 6 months for conversion. Started it up. Brake pedal is floppy, no pressure. Parking brakes work. I've tried bleeding the air system, restarting the bus. Air pressure system works but the main brake pedal is floppy and no pressure.


Help.

[Mountain Gnome]

I'm guessing you need a new treadle valve.

[Simplicity]

If you have equal air pressure in your tanks and the emergency air brake is working, then you just have to isolate the main pedal portion of the system.

This video may help.

https://www.youtube.com/watch?v=-R7J9BIjNEw

[Rwnielsen]

Interesting video thanks. Seems like a blockage or valve. Ice?

[Simplicity]

Another good video about air brake relays.

https://www.youtube.com/watch?v=f3LD8M0HKjo

[Derka]

I really appreciate everyone who posted.


This just in.


https://photos.app.goo.gl/nqQQubgVYqvZUQrv6
https://photos.app.goo.gl/zDEJ6iVgHNHwiLT3A


It looks like the steering column but the steering works. What is this fluid leaking?

[Simplicity]

When I'm in these situations, I clean off the parts, take close up pictures of any identifying markings, research it to discover what it does, how it works and any known issues.

Others may be able to look at it and identify it off the top of their heads, but I don't know what those are.

If the one with all the bolts in the picture that's got some thin liquid coating, I'm wondering if there's some kind of a hybrid hydraulic / air mechanism on your bus. If so, maybe that's hydraulic fluid, you have a leak and there's not enough pressure to activate your air system????

[Mountain Gnome]

It helps when you attach the pics instead of requiring a log-in to view them. Can't help, not logging in. Sorry.

[Derka]

I didn't see an attachment option on the quick reply. I see it on the normal reply. Here.

[Booyah45828]

Steering gear box.

Looks like the side cover is weeping fluid. Steering will still work so long as you maintain the fluid level.

As far as your brakes are concerned, you should verify you have air to your treadle valve first, but the valve is likely faulty.