Grain truck brakes

notjustair

Well-known Member
I think I know what?s going on but I thought I?d check with you all...

1974 Ford F600. Pulled it out of the shed to haul beans and no brake pedal at all. Brake fluid was all gone but no wheel cylinders had leaked. I put fluid in it and they didn?t pump up (it did it once before and I caught it before the lines were dry). I started bleeding the brakes and about the time I got a little pedal there was smoke rolling out of the tailpipe like you?ve never seen. It wasn?t antifreeze and didn?t really have a smell. There was so much that some ran out of the donut flange by the manifold. What does a good farmer do? Taste it! It was brake fluid coming through the engine.

My thinking is that the vacuum operated booster (on Chevy it is a Hydro-vac) has blown seals, the fluid crossed over to the vacuum side, and once there was enough it got pulled into the intake. Is this a reasonable asssumption?

It a eems the rebuild kit is no longer available but the unit itself is only about $250 at Napa so it isn?t like the old Chevy I had to do in the spring.
 
Seems like hydraulic brakes on old farm trucks are a never ending battle. Parts are expensive and hard to find in many cases. Sitting 10 months of the year can't be good for them.

Seems like guys with air brakes have less issues. Any parts are relatively common.
 
Booster it is. Easy enough. Sometimes the master cylinder piston seal is allowing BF to get into the booster. if so it may be the issue and (other than getting the BF out and cleaned up) it could be that as well. Jim
 
Leaking seals in the master cylinder may have deteriorated the diaphragm in the hydra boost. It has to leak out of the master cylinder to get into the diaphragms
 
Had the same thing happen to my C600 Dodge grain truck last year, when my truck dealer place sent it to me they told me to make sure and install the kit they were sending along in the vacuum hose to keep the crankcase gasses with the current blend of fuel or it would take the new out right away as that is what most likely too out the original one, its a tee vent apparatus that keeps the booster from getting what ever it is that eats the rubber in them,, your call just letting you know
 
I just went thru dealing with the HydroVac on a 66 c60. Yours is down on the frame right?

If you take the band off that holds the two halves of the vacuum diaphragm, separate it and it should have fluid in there. Or you might take the vacuum hose off the booster and it might show having fluid in there.

Changing out the booster isn't too bad....if the lines come free. They did easily on my C60. I just had to bleed the rr wheel. All the others were fine, but you need to bleed them too just to make sure.
 
Do you have the remote booster,with the master up on the firewall? Or,is the booster mounted on the firewall with the master mounted to that? Either way it will be the booster.If the master is mounted directly to it the master will be bad too.If I remember right the Fords had the remote mounted inside the frame rail,and a hose came up behind the seat for the booster exhaust to keep it out of the weather.It would moan at you when you stepped on the pedal.
 
When you take the booster off, look for a number tag.

That truck probably had several brake options, the booster needs to be matched to the brake system.

I would go ahead replace the master cylinder, or flush it with fresh fluid before connecting it to the new booster.

Those can be a bear to bleed. The more you can bench bleed it, the less air will be introduced to the system. Still, you'll want to bleed each wheel cylinder to get fresh fluid in the entire system.
 

Those chebbys are the only brakes I have had to reverse bleed to get the air out of the lines... The first shop I worked at worked on plenty of those trucks being the low man on the totem pole you got those good jobs, at least they gave you a hand full of brake line block off plugs to ease the pain... I would not start that job with out some block off plugs are you may be bleeding it till ell freezes over...
 
Only way for fluid to get into the booster would be from bad seal on rear of master cylinder. Replace both.
 
Hobo,
We work on a lot of those old grain trucks I just put
a booster on a 75 F600 today for the same reason.
A power bleeder is your friend on this job. Ours is
just a garden pump sprayer with a rubber hose. I?ve
made adapters out of old master cylinder caps.
What also works is taking the line loose at master
cylinder and hook the power bleeder on the metal
line. Fill the tank with brake fluid pump up the hand
pump , then go around the truck opening bleeders.
You can bleed the entire truck in less than 10
minutes. ( if the bleeders will loosen)
 
It has the remote with the master cylinder on the firewall and the booster on the frame rail. The truck has led a charmed life and only has 21,000 miles, so everything is easy to change or get loose. It should be easier than my 55 Chevy I did in the spring. Should be. And definitely easier than working on the mechanical brakes on my 35 Chevy grain truck.
 
I used a friends power bleeder this year for the first time. I had the clutch master cylinder go bad on my C600 Dodge, would NOT bleed out not matter what I did called my friend who ran a shop doing brakes ect for 30 years,, he said come over,, I did he told me how to do it,, he has a small rubber hose that will slip on the bleeder screws, like you said PUSH the air UP like it Wants to do,, I was on the road in less than 10 min, I will only bleed them this way from now on,, to try and push the air down I found is the dumbest way to do it,, You Sir are the first one other than my friend who ever suggested it,, and when I tell people it today they think I am nuts buts thats all good with me,, keep pump that pedal till your foot falls off LOL
cnt
 

reverse bleeding is a last option when all else fails because it will push crap into the master cylinder... My bad I had chebby on my mind they had dual wheels cylinders in the front they were a bear to get the air out of them by pump'N the brake pedal...

You will get a brake fluid bath swap'N out a chassis mounted brake booster have block off plugs in hand to lessen the bath.... Plus you want to retain all the fluid in the lines you can to ease the bleeding process....
 
sorry thought I was giving you a complement,, guess not,, Never mind I guess I know zip only been working on brakes 50 years now,, I will leave it up to the professionals to comment, I had ran three quarts of fluid through mine trying to push it down,, I highly doubt there was any Junk in my system as it was all new/reman units other than the tube and hose but I can see your point
 

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