question on grain truck brakes

notjustair

Well-known Member
I've been putting new brake parts on the '54 Chevy 6400 grain truck. It had a leaking front wheel cylinder. I put new shoes on the front, new wheel cylinders on the front, and new flexible lines all the way around. I bled it out last night (starting at the hydrovac and going out to each wheel). The thing stops on a dime but there is no pedal feel whatsoever. When the truck is off you can take your hand and push the pedal all the way to the floor with little resistance. It stops straight and doesn't pull and will lock up all four tires on the dirt road at about half pedal. It operates as it should but doesn't feel like it should.

I adjusted the shoes on the loose side when I installed them so I am going to go back and snug them up tonight. Any other thoughts?
 
you mite have "Not Just Fluid" in the lines ,,, you need a helper to get the very old fluid out "NOT Just Air" out ofthe lines . more than likely you have already done those duries ,,. hope you dont mind the play on words ,,..your 54 chevy has the master cylindars inthe floor like my 58 c-60 viking ,,.the viking also has no pedalfrom sitting 2 yrs ,,. i hope to fill it with dot 3 fluid ,, pump it thru andget the old ugly fluid out ,,. if not i will contact rock auto parts and get new brake cylindars ,, they had all i needed for the brakes on my 64 kaiser -jeep j 200 ,..good luck
 
Sorry, no help here but I have a similar issue with the hydroboost brakes on my 2002 Chevy 3500HD pickup. The brakes seem to work well but ever since it blew a brake line a couple years ago, it doesn't have any pedal feel.

I've asked many places and tried the few things that are suggested, but nothing has helped. Mostly I just get shrugged shoulders and blank stares from "experts."
 
I've never worked on these myself, but it comes up on Stovebolt fairly often. If I remember right, it seems like you do have to have the shoes set up fairly tight. Maybe ask over there if you haven't already.
 
yes, re-adjust the brakes for sure. Brake adjustment determines petal travel in drum systems, but I think you still have air somewhere in the system. Perhaps in the master cylinder, if it ever got low enough on fluid to allow air to pump through.
 
I never had anything that old, but had many Chevy trucks in the 70's and 80's. The brakes have to be adjusted correctly for them to work. If you can push the pedal to the floor on the 1st push, then they work, sounds like adjustment or master cyl problem. How does it stop with a load on it? Brakes on mine would get worn and need adjusting, truck would stop fine with the truck empty but with a load on they would not stop the truck. Was like pushing on a rock. good luck Tom
 
I had this happen when I do a brake job on an old classic car. If I do brakes, Wheel cylinders, Flex lines on an old car with Drum brakes. Some times it is best to replace the master Brake cylinder. For some strange reason the old master cylinder just does not handle all the new stuff and it needs to be replace. Most older trucks like G.M.C and Chevy's all drum brake I found in the past require to do this. After replacing it the pedal is hard and stops on the dime.
 
I would make sure they are adjusted up, so you can "hear" a slight drag when rotating by hand, that makes huge difference on pedal.
 
Air: a few things could a rubber line be exspanding (i've seen it) Out of adjustment on shoes or still air in the system. Master cylinder or hydrovac cylinder losing presser?
 
Boy, I sure wouldn't have road tested it before I had a firm pedal. My guess is air in the lines and/or master cylinder.

If I'm not mistaken, this truck has the master cylinder under the floorboard. A friend just did the brakes on a similar vehicle and had a heck of a time getting all the air out. He ended up reverse-bleeding the system with my <a href="http://www.brakebleeder.com/product-category/brake-bleeders/">Phoenix Systems V-12</a> and that did the trick.
 
it's more then likely the hydro-vac...about the only way to get the air out is with a power bleeder...we always had a heck of a time with ours....
 
"starting at the hydrovac and going out to each wheel"

Wrong!! you start at the farthest wheel, then next ending up at the hydro.
When I bleed brakes I just open the bleeder and let them gravity bleed, put a little spit on your finger and put on bleeder, you will see a bubble telling you that air is being displaced by fluid.when fluid shows up let it go some more, then on to the next closest wheel.
 
Nope - repair manual states that both bleeders on the hydrovac must be done first before any wheel cylinder and with no vacuum on the system. Page 5-27...
 
Air: the guy on the v12 is probably more modern. But I had (still have) a brake bomb Fill it will fluid (gallon or two) Hook to master cylinder (adapters needed) add air pressure and start bleeding. Years ago we brought a few stubbon wheelers and (dual wheel cylinders too) around with it.
 
I have worked on juice brakes on trucks for more years then i can count and even before you start to bleed them you want to get them adjusted up . This can be a little tricky as this is a fine line between not enough and to much . Now i have never worked on Chevy truck brakes but Ford and I H and with me it is a FEEL thing for me as you want a slight drag and you should have a slight drag To much and they will get hot not enough and you will not have good stopping and may find the need to have to PUMP the pedal . You should have full brqaking with around and inch to inch and a half of pedal travel .
 
I rebuilt the brakes on an older model dump truck with dual wheel cylinders at each wheel and a hydro boost. I could not get proper brake pedal feel until I adjusted the shoes out until the adjuster would not turn further, and the brake drum was locked tight. Then back off the adjuster until the drum rotates but with a slight drag. This needs to be done at each wheel.
 
No help for your situation, but a recent auction I attended, they had the one-owner 1973? C70 Chevy with grain box, seemed like 30K miles. The auctioneer was very careful to show the crowd the bill from local auto/truck repair for $4100 for complete new brake system. Truck sold for $3700. ouch.
 
Is the pedal low but if you pump the pedal it gets higher?Is the pedal then solid?If so,it's bled out but needs adjusting. Years ago when I worked on hydraulic drum brakes on trucks,what we had always had 2 adjusters on each wheel-1 for each shoe.You have to adjust each adjuster to make its shoe drag on the drum.Usually adjust until you can't rotate the wheel,back off a little,do the other adjuster til it locks up the wheel and back off.Repeat at each wheel.Mark
 

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