MCI-9 Squealing Air

[Kwajdiver]

When I apply my parking brakes, I get a squealing sound from the air system.  First I thought it was coming for all brakes or it could be coming from something in the last bay.  If I play with the pull (air) switch it will go away, sometimes.

How much is this going to cost me   

Thanks in advance for the input.

Bill

[Dreamscape]

Hi Bill,

Sounds like your brake switch is in need of a rebuild or replaced, something is not seating properly when you hear air bypassing making a noise. That is why sometimes you fool with it and it goes away. Air valves that make noises are usually gummed up or worn out or both.

Paul

[Kwajdiver]

Paul,

Where is it located on a MCI-9?

Thanks for the help.

Bill

[Dreamscape]

Bill,

Does the parking brake button have air lines to it? Not sure if its similar to mine or not. It might be a switch that activates the valve, the valve is where the problem could be. I am sure others who are familiar with MCI's can be of more help. Where is your parking brake button located?

MCI owners please provide Bill with your expert knowledge.

Paul

[Kwajdiver]

Paul,

Yes, I believe it is an air switch.

Bill

[Hartley]

The brake light switch is in the spare tire compartment up next to the brake valve (up on the floor level)

You have to lay on your back and crawl in to get to it. 2-wires and Napa or any truck place will have compatable switches in stock.

Mine was leaking and whistling , I looked at the book and it is rebuildable but for $5 it was easier
just to change it out. Screwdriver and pair of pliers. 10 minutes of pain...

Dave....

[Kwajdiver]

Brake Light Switch      Really

But the sound seems to coming from the last cargo bay.


Bill

[TomC]

Sounds like you may have a blown parking brake diaphram on the brake cans.  If they leak, they can back feed into the other cans and make a hissing sounds.  Good Luck, TomC

[Kwajdiver]

Could the Inversion Valve be the problem?

Bill

[NJT 5573]

Think Tom  is right. Get it safe to release the brakes, listen for air leaking at the drive axel brake cans with the brakes released. If it leaks under these circumstances, you are out of service on the spot until the brake can is replaced. Don't burn your bus down.

[buswarrior]

Hello Bill.

DD3 brakes, the kind on your MC9, require a little diagnosis to properly identify the right strategy to keep as much of your money in your pocket and time spent replacing parts to a minimum.

As noted earlier, get the bus into position to crawl underneath, block the air suspension so you are safe, run the bus to fill the air system, and turn the motor off, to be sfe and so you may hear, then carefully seek out a source of leaking air, spray bottle of soapy water at the ready, under these three conditions:

parking brake released
parking brake released, full brake pedal application ( need a stick or a helper)
parking brake applied

restart engine and rebuild air as neccessary, not with you underneath, please!

You will want access to the relay valve exhaust and the inversion valve exhaust at the rear, and the brake pedal exhaust up under the driver, against the bulkhead, follow the brake pedal linkage. Also familiarize yourself with the location of the pressure regulator attached to the inversion valve and check it too while you are under there, just for external bubbles. It should be air tight.

You must note from where any air is coming out. The source of the air, under which condition, will pinpoint the offending circuit or part.

[Kwajdiver]

Thanks, I will start looking for that in the next couple of days.
Had plan to start looking today, but, as luck would have it, it wouldn't leak.

Thanks again.

Bill

[Kwajdiver]

Guys,

In the passenger side rear engine door, above the transmisson, are two air regulators.  The one on the right, is leaking.  Could this be my problem?  What does it take to rebuild this?


Thanks for the help.

Bill
Currently in Phoenix

[Kwajdiver]

AND there's more,,,,,

Looks like the bottom of what I believe is the Brake Valve, located under the driver in the driver tool compartment, it is leaking on the bottom.

How do I rebuild this?

Again Thanks,

Bill

[Stan]

My suggestion is to buy factory rebuilt/exchange components for the brake air system.