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Need Help Understanding B-30 Braking System


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I need some help understanding the braking system on my B-30. First off, it does not have air brakes, there is no compressor. However, there is copper tubing that looks like it could be deliving a vacuum to what I would otherwise call the air tank. This "air tank" or vacuum?? tank is located inside and below the left rail just behind the cab. Above the tank is some sort of gizmo that is connected to the "air tank" and has a lot of hoses and tubes connected to it (I know I sound lke my girlfriend trying to describe what I see). This gizmo is inside the left rail (see pic below).

To complicate, there is a control on the right side of the steering column opposite the turn signal switch that looks like some sort of air control. Copper tubing that appears associated with the tubing to the "air tank" appears to have been connect to this control but has been disconnected and plugged - there are two tubes coming up the steering column ending in opposite ends of a tee. The branch of the tee is plugged.

The brake pedal will go to the floor with no resistance. There is the usual parking brake lever to the right of the gear shift which, when applied, seems to produce a barely detectable drag on the rear wheels.

Notice the pillow bearing in the PTO shaft. Wonder if this can be done an newer trucks because .... yep, its wood. About 4"x4"x2" thick with a shaft size hole at the center. It was probably needed when the truck went from milk truck duty, where the PTO ran the loading pump, to dump truck duty where the PTO needed to extend back to the hydraulic pump beside the scissor hoist.

Folks want to know why I didn't leave that ugly old dump body behind. I point out 45 feet, or so, of heavy channel in the rails (price that stuff lately?) ... and then I point out that there is a scissor hoist of at least 10 ton plus a hydraulic pump under there. Folks just say, "Oh". Utilized properly, that ugly old dump body is probably worth a good deal more than I paid (just under scrap price) for the whole truck, which I paid $400 to have it hauled 60 miles home.

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Edited by dmlinton
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Best regards, Dennis

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im guessin you probably need wheel cyliners. they go bad in a hydraulic system from setting around,. the air tank is actually a vacuum tank. shouldn't be used as an air tank because it is not as thick . the big canister is the hydrovac. kinda like a modern brake booster, helps the brakin along. even if the hydrovac is bad , you still should have a little bit of brakes and resistence. put some fluid in the reservoir under the floor and bleed it, im sure you probably have a bad wheel cylinder.the hydrovac gets vacume off the exhaust manifold. usually had a 5/8 copper line plumbed into the hole In the manifold back to the ''air tank''. the hand brake is only on the driveshaft. its used only for parking and emergencies. if you pull it and it doesn't do anything im guessin someone left it on and wore out th lining on the e brake. there are places that will reline these or abou $100 to

150 or so.

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Thanks, Maddog. It all makes sense now. First thing to replace is the vacuum tank - it turns to dust pretty well wherever I poke it with my finger.

Quit poking at it....it'll be fine.....:P lol

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Lack of planning on your part does not constitute an emergency on my part....

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I have a similar brake system on my 1955 B20. My brake system is dead just like yours, sat for nearly 20 years. I haven't yet started to work on it but reading about it on the web, setting up the Hydrovac isn't quite as straightforward as you might imagine. And, if you don't follow certain procedure steps in order you can damage a newly rebuilt Hydrovac. Lot's of info on the web including how to rebuild a Hydrovac if your up for the adventure. Just Google Bendix Hydrovac. I don't know much about them so will gladly defer to the experts on this very site. Gotta be some old timers that have experience with these systems.

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Rebuilt hydrovacs are commonly available; it's not worth trying to do it yourself.

Obviously you need to replace the entire system including the steel brake lines. If you can't borrow one spend the money, about $200.00, on a good flaring tool from Eastwood or one of the other vendors, you will be glad you did.

If you cannot find wheel cylinders the originals can be re-sleeved by a restoration shop such as White Post.

I assume you have your truck's info from the Mack Museum. This should provide details about the braking system and how the components are installed.

One hint when you start bleeding; do the hydrovac first. Then move on to the furthest wheel. Depending on how the wheel cylinders mount you may have to use positive pressure to force brake fluid in. (Some mount in such a way that the bleed opening is lower then the bore, trapping air in the bore) I use a garden sprayer I converted to force brake fluid into the system at the master cylinder and then I bleed the MC the conventional way.

The "T" shaped device you described is probably for the trailer brakes. That is why it is blocked off.

Money, sex, and fire; everybody thinks everyone else is getting more than they are!

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Since it has set for any period of time you will have to go thru the whole brake system rebuilding or replacing everything from the master cylinder to the wheel cylinders. brake fluid draws moisture and corrodes everything as well as the rubbers disintergrate over time. and the steel lines rust from the inside. The extra time and expense WILL SAVE YOUR LIFE!!!

I got a rebuilt Hydro-vac for my Ford F-600 from BEPCO, Winston Salem NC 336-760-0740 or 800-735-1154 came FedEx in about 2 days.. Save the box and styrofoam for your core return.. I do NOT know if there is a way to add a dual master cylinder to this type of system. I have not done so on my F-600.

The control on the steering column MAY(??) be a hydraulic brake lock,in addition to the parking brake. A lot of fire trucks had them..I doubt if it is a trailer application valve as vacuum braked trailers were long gone by this era..

Your hand parking brake applies to the drive shaft right behind the tranny, some are drum and some are disc. First soak the linkage good with panther pi$$ and the see if you can adjust it up stronger if there is any lining on it.

If what you are describing as a "scissors lift" is one which lifts the whole body straight up then dumps it, SAVE IT as they are scarce.. They were used only by coal delivery trucks from the 20's to the 60's and a few roofing companys.

You have a good looking truck.. Keep the pictures coming!! You will find plenty of help on this board.

Brocky

Brocky

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Had White Post rebuild hydro and master cyl on B30 they did a great job, can send pictures of how everything is plumbed if you need them. Napa has all wheel cylinders pretty cheap.Made all new brake lines. If you need help with part numbers let me know.

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...

I assume you have your truck's info from the Mack Museum. This should provide details about the braking system and how the components are installed.

...

I have not put in a request to the Mack Museum yet. How does one go about doing that? I checked the museum web site but do not see a page of details they need or a form.

The only identification tag I have found is on the passenger door but I understand that it may not be reliable. I cannot find the chassis or rear end tags but there is a lot of gunk in some places that may be

hiding them. I have to find out precisely where to look and then go mining for the tags.

Best regards, Dennis

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Just send them a letter, along with a suitable donation, asking for the history of the truck.

The vin should be on the title or registration, assuming you have either document. You will receive a service manual, the build sheet, and any other history they have on file about your truck. Generally takes 6 - 8 weeks to get the info.

I still think the "T" shaped device is a vacuum trailer control because you said it was hooked to the vacuum tank at one time. Mico-Locks, hydraulic brake locks, do not connect to the vacuum system and you would have a small handle on the dash to apply it if it were on the truck.

There will also be a screen in the vacuum system prior to the hydrovac designed to keep dirt out of the hydrovac and the hydrovac will have some type of vent screen to prevent dirt from entering via the vent line.

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Money, sex, and fire; everybody thinks everyone else is getting more than they are!

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Thanks, fxfymn. The VIN is, indeed, on the registration, which is now in my name. Wasn't sure if that as enough info. I will get the request and "fee" out this week.

Edited by dmlinton

Best regards, Dennis

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