The Stovebolt Site Forums The Parking Lot Big Bolts New here, need help! Brakes 72- C50

I am trying to purchase a 72 C50 dump truck. I live here in massachusetts and this truck is unbeliveably solid. floors rockers etc. unheard of in these parts. Any way my question is on the brakes, It has a manuel master cylinder on the fire wall, 2 lines out of it, then it has what appears to be regular drums in front. In the rear it has two wheel cylinders on each wheel (prety standard) now the hard part it has TWO what look like vacume boosters under the drivers side of the cab. I did some search on your site and they look like "hydro vac" boosters. is this right for the year or am I wrong.The set up looks factory. The master is dry No brakes. I was going to pour fluid in, try to bleed them and check for leaks. is there any thing I should know before doing this? Also can I use DOT 3 brake fluid. I am a Chevrolet car/light truck mechanic and have little experiance with medium duty trucks. No one around here remembers them much because in new england most have gone to scrap years ago. This will be my first big bolt. Any info would be great. Thanks

Does any one know about any junk yards in norther mass/southern maine/new hampshire that have any older medium duty big bolts of this vintage?

Hy rust master, if it is a dual master cylinder setup, then one booster is for the front, and the other is for the rear, lots of changes going on in those years, don't be affraid to ask more questions.

Higher grade brake fluid is specified for 1967 c50, so is probably yours. Higher brade br fluid as higher boiling point, & better flow charastics in cold weather. There are big bolters that use DOT 3. However; if you plan on haul'in a lot of weight with frequent braking, I'd consider using better fluid.
Do you have any idea how long it's been since the master cyliner resivour has been empty? How long since breaks were last used? Did they work? If you're un sure if the brakes work. I'd use DOT #3 just 'cause it's cheaper $. Then when brake are working, I'd upgrade the fluid later.

Also; Due vacuum booster(s), Be sure the engine is NOT runing when you bleed brake lines.

Welcome aboard

CFFC
Don

dot 3 is fine,,,it is a hydro unit,,if you are going to load and drive on roads take a good look at all lines both steel and rubber,,if sitting for along time master and wheel cyl's could need work same with hydro...doc

Welcome Rust Master. As you can see you've come to the right place for ideas and information.

Take some time to check the Tech Tips and other forum locations. Nobody has to reinvent the wheel here.

We'll be interested in your progress.

I just went through the complete brake system on my 65 C 50 wrecker. I used dot three on it.My lines were rotted right off from rust. I bought everything brand new /master -all six wheel cylinders and a rebuilt hydro vac.I had to make and bend all new lines. A good source for parts is napa. I got my cylinders through a local dealer named cowans auto right here in greenfield mass. Where in mass are you. It is nice to have another crazy person amongst us. If I can help any further let me know. Been thier and done that.

First, look for signs of the leaks at each corner and at the master. If you can find a trace of where the fluid went, I'ld bet it's all in the hydrovac. Be sure to fix the brakes right, it's the most important system on a truck, especially a big one,
Scott

Thanks, I want to try dot 3 just to see where it is leaking. lines look good most look to have been replaced. I was concerned that the hydrovac is where the fluid is going. I'll put some dot 3 in and check for leaks.Thanks for the info. Biglou55 know any good yards around here? I'm in Gloucester MA. I'll try to get some pictures up when I can get some. ( I know you guys love pics)

BTW, has been off the road since 2000. Thats the last inspection sticker. don't know how long the master has been dry.I'm trying to buy her form the local scrap Guy. She was given up as scrap! which I can't believe due to the shape she is in. They probably stopped using her due to the brakes? everything else is in pretty good shape.

Looked at her again today. Definitely has TWO hydrovac boosters. has anyone seen this setup? does one go to each rear wheel or one front and one back??? looks like they go to the rear? hard to see where they go. The master is a duel resivor, the cover bolts onto it not a clip on. truck is a 292-6cyl 4 speed with low 4 gears all together. does NOT have a 2 speed rear. should this truck have a 2 speed rear?? pto driven dump works like new. Does any one have a hydraulic schematic for this type of system?? I can't find much info online other than the hydrovac itself.

Rust Master,Those were great trucks.I worked on them as new when I worked for the Chevy dealer.The brakes sound like it is a Bendix dual hydrovac system.I have the service and overhaul manuals for the 1971 C40-70 that should be the same system as your '72.Send me a PM if you need them.

My wrecker has a handle in the cab on the dash that has two lines that go too the hydrovac. It locks up the back brakes so I can winch something up to it. Do you have it on your dump that might be why you have two hydro vacs. just a guess.

gtow69 you have a PM could use that manuel, biglou55- there is no lever I could see anywhere to the hydrovac? some one around here said one may be front and one rear??? the problem is they don't appear to go to the front?? I guess I really need a manuel.