Replacing Air Brake Chamber

[tcolburn]

Motoring along on I-80 Sunday, we struck a piece of shrapnel (looked like a metal grating of some sort) that was sitting right in the middle of our lane. I thought I straddled it well enough to avoid damage but as we exited the Interstate the rear brake pressure dropped quickly and the alarm came on. Managed to get home carefully and got the coach parked in its storage slot. Upon inspection, I discovered a hole in the left rear air brake chamber! Here's the question: is this part something I can try to replace by myself? I've looked at several YouTube videos and it certainly seems doable: cage the spring, disconnect the air lines, remove the clamp, and then reassemble with a new part... Any words of wisdom? Sure would rather not have to get the coach towed to a shop!

--Tim C.

[kaypsmith]

I have replaced many of them, yes it very doable if you have the correct tools. I assume that this one is the drive axel, what a shame as it is pretty expensive, but some good news, if you have collision insurance, you should report it your insurance company, in most cases they will usually pay their part because it is an accident. By the way, do not attempt to take that chamber apart if it is on the drive axel, the parking brake spring resides there.

[desertdeals69]

Not that difficult to do.  Too bad you don't live in Az as I have a couple of new ones in my garage, you could have one!

[garyreed]

If you are just going to change the chamber itself you are right. To make it a little easier, before you cage the spring, put vise-grips on the shaft next to the braket on the front side by the adjuster and it will make it faster going back together. Looking at the picture you cannot take the dangerous clamp off, just make sure you get the bolt firmly seated when you cage the spring.

If you are loosing air without the stepping on the brake pedal you may want to also look at the air lines around the chamber. You should be able to pick one of those up for under $80. It may also be cheaper to buy the whole assembly and use what you need.You also need to check the section bolted to the braket to make sure it is not bent or cracked.

Gary

[kaypsmith]

Tim's problem is the chamber itself, not the diaphragm. As a get me there, one can cap the air line to that brake chamber if necessary, just remember that is a limp only procedure.

[wolfe10]

That is a very common OTR truck part.  Unless it is truly an emergency, just get a new one installed.

The correct procedure (caging the parking brake spring) is critical from a safety standpoint. Not complex, but the power in those components can KILL OR BADLY HURT YOU if you don't know what you are doing.

[tcolburn]

Hey, everyone--thank you all for your responses and excellent advice. I've got a new unit on order from Freightliner and should have it in a day or two. I will be back to update the group on my progress. As Kay noted, it's just the chamber housing that's damaged. And I am parked safely in our local storage area, so no emergency. You bet I'll be careful about the spring, too! See you soon.

--Tim

[tcolburn]

Success! And thanks to all for your advice and support. As jobs go, this one turned out to be relatively uncomplicated. Was very conscious of all the safety warnings, so I worked slowly and methodically ('course, everything I do these days is slow and methodical!). Gary, your advice to use vise-grips to hold the shaft was spot on--made it very easy to reassemble all the parts. I purchased the entire unit and just used the clamp, diaphragm, and air chamber/spring brake (referred to as a "piggyback kit" in some of the documentation I found) so that I wouldn't have to mess with the slack adjuster and clevis, nor have to measure and cut the new shaft. Nothing else was bent or damaged.

Hardest part was getting the air line nipples out of the old unit, but a gentle application of heat finally did the trick. Interestingly, I discovered damage to the diaphragm under the hole in the chamber housing so I was happy to replace it.

The whole operation only took three tools (well, four, if you include the torch): 9/16, 3/4, and 7/8 inch wrenches. Luckily I have some GearWrenches--made it a lot easier. But, wow, my muscles still ache from cranking up that caging bolt! Here's how the new one looks. And it works perfectly.

--Till next time, Tim C.

[wildebill308]

Great job and thanks for the update.

Bill

[michaelp775]

I recently replaced both my fronts . one other trick is take the air fittings off while it is on the vehicle. 

[tcolburn]

4 hours ago, michaelp775 said:

I recently replaced both my fronts . one other trick is take the air fittings off while it is on the vehicle. 

Good idea. Didn't think of that while I was under there! --Tim

[garyreed]

Glad you had success and saved a little money in the end. Sounds like you also gained a little confidence for the next prodject. You are right about taking it easy if you are not sure, even good mechanics will get tripped up if they get in a hurry.

This forum is full of people with lot's of experiance on lot's of topics. Thanks for asking the questions and showing pictures (I have not learned that one yet) it will help others alot.

Gary