A Wild Geese Chase...parking brake M923

[Swamp Donkey]

A Wild Geese Chase...Parking Brake M923

So when I first acquired my M923A0, and up until about a month ago, there was only one goose in my intake stack...that let me know when I squished it with the parking brake. Well...now I have about four in there...

All joking aside, I'll explain the issue. The TMs and P2P program, while helpful, have not allowed me to pinpoint the problem.

The truck has always had a crisp, consistent report when the parking brake is applied. For about the last month the report has either been short, long, weak or strong but a lot of the time it sounds like it's supposed to. Short would be half a second while long would be about 5 seconds. Regardless of the inconsistency of the report and lack of other symptoms, something doesn't appear to be working correctly. This bothers me, especially on the brake system.

I don't know how long it should take the spring brakes to apply after the handle is pulled as I never really timed it until after this started. They take about 5 seconds to apply no matter how long the report is, and this is a consistent time. This is figured by manually activating the spring brake switch on the parking brake handle while slowly rolling in neutral. I start counting when the switch is activated and stop when they stop the truck. They always apply and always hold like they should, which has been verified by manually activating the spring brake valve on the lever to bypass the drive line brake.

After this all started I decided to disassemble and inspect all the valves in the brake system. This would serve two purposes: I'd know the condition of every part of the brake system and I'd eventually run into the cause of the report inconsistency. The second part never happened. I've been through all the "simple" valves (quick release, single check, double check, etc.) and haven't found anything to make a difference. Nothing I've been through so far has has the slightest bit of corrosion, moisture or contamination. Everything has been surgical clean. I have not been through the treadle valve, the relay valves for the ABS, the LQ2 or the PPV.

Looking through the P2P it appears that the quick release valve in the step box is what releases pressure to apply the spring brakes. The original was spotless and the internals appeared to work on the bench. I replaced it anyways as I had a spare. This didn't change anything either.

I also know the report can change depending on pressure on the treadle valve. My testing was done without any use of the treadle valve. Sitting still while not touching the treadle valve I would manually operate the switch and the report can sometimes be all over the place.

So here are the questions:

What valve actually makes the noise in the intake stack?
Does the treadle valve have anything to do with the spring brake release and application?
How long should it take the spring brakes to apply when the switch is activated?

I feel I'm missing something easy but I don't want to find this was a minor symptom of a major problem.

 

[Suprman]

It's a release of air from the brake system. The trucks will make a wide variety of honks and groans from the stack. It's normal. But somewhat annoying.

 

[porkysplace]

Great title that will really help future searches.

 

[bchauvette]

My ruck take awhile for the spring brakes to apply after lifting the hand brake. If you don't remember you can actually get out of the truck before they engage.

 

[Swamp Donkey]

It's a release of air from the brake system. The trucks will make a wide variety of honks and groans from the stack. It's normal. But somewhat annoying.

Yes, but what actually makes the noise? I understand its necessity and I understand the function. I don't have a problem with it happening per say, but more of a problem with it changing. Inconsistencies bother me unless I can determine the reason for them.

Great title that will really help future searches.

Thanks. It took me a minute to come up with a catchy one...

My ruck take awhile for the spring brakes to apply after lifting the hand brake. If you don't remember you can actually get out of the truck before they engage.

This has been my experience too. I have to remember this when parking on a hill. While the drive line brake is adjusted and funtions properly, I don't get out until the spring brakes have a chance to apply.

 

[zout]

I finally bought one of the Duck Calls and stuck it on the stack air outlet line - now It always sound like a duck call instead of them honky irritating sounds.

 

[Swamp Donkey]

I finally bought one of the Duck Calls and stuck it on the stack air outlet line - now It always sound like a duck call instead of them honky irritating sounds.

Hmmm...duck call with a wetland camo paint scheme. Haha this has potential.

 

[hndrsonj]

What is a M923A0? Never heard of one.....

 

[Coffey1]

He was most likely misinformed like I was.
Swamp its just a plain old M923.

 

[hndrsonj]

He was most likely misinformed like I was.
Swamp its just a plain old M923.

Just my strange way of teaching....

 

[Swamp Donkey]

Just my strange way of teaching....

Oh really...well how about schooling me on the answers to my three questions. Or is the teacher not well versed on the subject?

The use of the designation "M923A0" let you know exactly what I was dealing with from the very first post. This, as opposed to someone stating "M923" in the original post, just to find 10 post later they shortened it down from "M923A2". You proved my use of the designation as valid, yet you've taught me nothing yet...