Air leak

[Disbus]

What started out as a slow leak from the rear brake circuit now has become critical. The bus will not reach pressure front or rear..after turning off the bus i can hear air escaping from directly below driver's area.

2003 BB TC2000 FE.

Need help fixing. Anyone who can help me near Joshua tree national park?

Could be a simple leak, cracked hose etc. I use a wheelchair so i can't get under there go identify.

[CHEESE_WAGON]

Delete... double post.

[CHEESE_WAGON]

This is why it's a good idea to check this sort of thing and repair it before it gets this bad, folks. It kind of sounds like the air spring for the parking brake release.

How do you know it started in the rear circuit?

[Disbus]

Recently i replaced a quick release valve in the rear. Helped but didn't fix the leak down in the rear. Then short stops i lost all my rear air.

[CHEESE_WAGON]

Leakdown on pedal application is probably a brake chamber. But you could also have a bad / weak compressor or governor. Treadle valve (at brake pedal) could also be bad. Also check lines in these areas.

[Disbus]

Replacing a pressure relief valve on the secondary air tank should fix it. $32.

Hopefully the only problem.

[CHEESE_WAGON]

Originally Posted by Disbus

Replacing a pressure relief valve on the secondary air tank should fix it. $32.

Hopefully the only problem.

It'd be nice if it were that simple, but I doubt brake application would make a difference if it were. Leakdown on application points more to brake chambers or treadle valve IMO. Just my $0.02.

[Brad_SwiftFur]

Last vehicle I had that would not build air pressure, it turned out to be the air dryer, the purge valve so gummed up it was sticking "open". Also could be air ride system (won't leak until the protection valve opens at around 60 PSI).

[Native]

I am interested to see what you find is the problem and the solution.

[cadillackid]

What brad said, air dryer and air springs in the rear( leveler valve and a bag) are 2 areas that have given me air leaks.

On most fronts engine busses a lot of stuff with air system happens near / under driver seat so it’s tough to diagnose without getting someone under it. The tanks and dryer are in that area.

[CHEESE_WAGON]

Originally Posted by Brad_SwiftFur

Last vehicle I had that would not build air pressure, it turned out to be the air dryer, the purge valve so gummed up it was sticking "open". Also could be air ride system (won't leak until the protection valve opens at around 60 PSI).

I can see the dryer / purge valve sticking, but would a skoolie even have a protection valve? I thought that was a semi tractor thing for combination vehicles if the trailer breaks away? Or are you talking about a different type of valve?

[cadillackid]

Originally Posted by CHEESE_WAGON

I can see the dryer / purge valve sticking, but would a skoolie even have a protection valve? I thought that was a semi tractor thing for combination vehicles if the trailer breaks away? Or are you talking about a different type of valve?

yes school busses have protection valves for accessories.. the air suspension, stop sign, air door, air seat, etc are all behind a protector valve.. usually gives you about 70-80 PSI of air in your tanks. . enough your springs wont apply and you'll have decent service braking pressure to get you stopped and safe. anbd if you need to move the bus you can..



its hard to speculate without the OP having someone who can crawl underneath for him and look..

[Booyah45828]

They're talking a pressure protection valve, and like Christopher pointed out, it only allows air to flow to the accessories if the tanks have over 65-95 psi.

A tractor protection valve, which won't be on a school bus, is there to protect tractor air pressure in case of trailer loss of pressure.

[Booyah45828]

Someone is going to have to crawl around underneath and find your leak. We sadly can't do that for you online. That same someone is likely going to have to repair your leak as well, so hopefully find somebody handy with tools and is somewhat mechanically inclined.

If you can't do that, you're best bet is to call some sort of road side service. I doubt it will be cheap, but hopefully they'll get it fixed for you and you'll be back on the road.

[Disbus]

This pressure relief valve on the secondary tank looks to be the culprit. Clearly leaking air 100% of the time. You can see the ball valve is not seated, rattling around inside. Should have the new one in today or tomorrow.

[Disbus]

Originally Posted by Disbus

This pressure relief valve on the secondary tank looks to be the culprit. Clearly leaking air 100% of the time. You can see the ball valve is not seated, rattling around inside. Should have the new one in today or tomorrow.

[CHEESE_WAGON]

I hope that this is the OP's problem, I just don't see how that would cause increased leakdown on brake application by itself.

[Disbus]

I never had leak down as you describe. Did i missspeak? It worked, then didn't. I had low pressure, frequent compressor working. Trying to get it fixed when it gave up completely.

[CHEESE_WAGON]

Originally Posted by Disbus

Recently i replaced a quick release valve in the rear. Helped but didn't fix the leak down in the rear.Then short stops i lost all my rear air.

Originally Posted by Disbus

What started out as a slow leak from the rear brake circuit now has become critical. The bus will not reach pressure front or rear..after turning off the bus i can hear air escaping from directly below driver's area.

These two indicate leakdown as well as application pressure outrunning the compressor.

Regardless of the cause, this should be a lesson to anyone. Fix it before it gets this bad.

[Disbus]

Ok, yes daddy. Enough lecture