CTIS Brake Leak M923A2 HELP

[JOR]

Passenger side rearmost axle leaking air from the CTIS brake. Pressure dropping exceedingly fast when the brakes are applied.
The leak is coming from inside the brake drum. The brake drum doesn't want to come off. Is there a way to get to the ctis from the back or do I need to remove the drum to find what is leaking? I can't locate this in the manuals.
What can be causing this leak, and how do I go about locating it, since I'm having trouble getting the drum off?

 

[74M35A2]

Sounds like you just have a ruptured service brake diaphragm. There is no such thing as a CTIS brake. A ruptured service brake diaphragm will allow air to travel down the push rod tube and into the drum. Easy and low cost fix, don't need to pull the brake drum, but study up well on how replace a brake can diaphragm, as they are spring loaded with deadly force. You need to "cage" the brake can before disassembling the clamp ring, this requires a $5 brake caging bolt from NAPA or other truck shop. Study it very well before attempting, or have somebody else with experience doing such before you disassemble it. Diaphragm sizes are posted here elsewhere. Total part cost to repair should be about $20 including the new diaphragm and a caging bolt.

 

[JOR]

Inner seal

Sounds like you just have a ruptured service brake diaphragm. There is no such thing as a CTIS brake. A ruptured service brake diaphragm will allow air to travel down the push rod tube and into the drum. Easy and low cost fix, don't need to pull the brake drum, but study up well on how replace a brake can diaphragm, as they are spring loaded with deadly force. You need to "cage" the brake can before disassembling the clamp ring, this requires a $5 brake caging bolt from NAPA or other truck shop. Study it very well before attempting, or have somebody else with experience doing such before you disassemble it. Diaphragm sizes are posted here elsewhere. Total part cost to repair should be about $20 including the new diaphragm and a caging bolt.

Pardon my lack of knowledge, I’m posting on behalf of my boyfriend, whose truck it is.
Now He thinks it’s actually an inner seal inside the drum. Any recommendations on how to get it off? Thanks so much for your speedy reply.

 

[74M35A2]

A few minutes of proper diagnostics will save you a ton of un-necessary work. Yes, the CTIS has 2 air seals within the hub. Disconnect the CTIS power plug on the control head and it should stop that problem, if that is it. Would only need to be fixed if you want CTIS operational. But, you said pressure drops when brake pedal applied. This means it is brake related, and not CTIS related, and easily fixed without even taking a tire off.

Is the air leak happening when the parking brake is released (only), when the brake pedal is pushed (only), or when the CTIS attempts to inflate a tire after ignition on (only)?

Start the truck, let it build up pressure if it can, then try the three things above, each individually.

 

[JOR]

A few minutes of proper diagnostics will save you a ton of un-necessary work. Yes, the CTIS has 2 air seals within the hub. Disconnect the CTIS power plug on the control head and it should stop that problem, if that is it. Would only need to be fixed if you want CTIS operational. But, you said pressure drops when brake pedal applied. This means it is brake related, and not CTIS related, and easily fixed without even taking a tire off.

Is the air leak happening when the parking brake is released (only), when the brake pedal is pushed (only), or when the CTIS attempts to inflate a tire after ignition on (only)?

Start the truck, let it build up pressure if it can, then try the three things above, each individually.

When depressing foot brake all air in the primary air tank is rapidly depleted in less than 60 seconds when the truck is off, and parking brake applied. Also when truck is running and parking brake is not engaged the same thing happens. Leaking noise is coming from inside the brake drum.
A slow leak seems to be happening 60psi over 8 hours or so when left overnight but the main issue is the massive loss in pressure when brake pedal is pushed (only)

 

[74M35A2]

OK, it is brake related, no need to pull the brake drum or hub. Here is how it works, and this will make sense to you and him:

Park brake: Opposite of what people think. Uses air pressure to "release" it. No air to it, (parking brake lever on) and it is "on", forcing the brakes on with spring pressure. When park brake lever is "off", it sends air to it, pushing the spring inside the can, and it releases to "off" position. This works a little opposite of how people initially "think" it should work.

Service brake (brake pedal): Basically opposite of above. Simply uses air pressure from brake pedal to activate the brakes.

You have air leaking when air is sent to the park brake and/or service brake can. Replace the diaphragms in the brake cans for that wheel, and it should resolve your problem. Then, go through, and change the rest of them also, as they are likely in nearly the same condition, and it is a low cost and wise thing to do.

The slow leak over 8 hours is nearly considered "normal" for the age of these trucks. Nearly everything would need to be refreshed to alleviate that.

There is nothing air related under the brake drum regarding the brakes, just the friction material and activation mechanism of the brake system. The CTIS passes air through the hub, but that is not your issue.

Do not let your boyfriend take the brake cans apart until he reads up how to do so. If he just loosens the band clamp, it will fly apart and tear his face off, closed casket type of force.