Brake issues
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Junior User
Joined: Jun 2010
Posts: 94
Likes: 0
Brake issues
So, the PO upgraded to disk fronts and apparently just found a random (Ford?) master cylinder. Im now having a problem with the brakes working sometimes and the pedal going to the floor other times, sometimes a combination of the two while approaching a stop (very scary). I was gonna start w the master cylinder but found that it isnt the right bore size for the booster rod. Now Im stuck because I cant figure out how to proceed.
Keep ordering master cylinders until I find the right one to fit the booster rod(Napa Auto will hate me, and the 66 Galaxie didnt work)?
Start with a fresh new set up, but for what make, model, and year? Will it mount to my existing set up? What about the pedal rod length?
And no, it didnt leak fluid even though the rod to bore size was off by at least 1/8".
Keep ordering master cylinders until I find the right one to fit the booster rod(Napa Auto will hate me, and the 66 Galaxie didnt work)?
Start with a fresh new set up, but for what make, model, and year? Will it mount to my existing set up? What about the pedal rod length?
And no, it didnt leak fluid even though the rod to bore size was off by at least 1/8".
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Not enough info to help. Is there a power booster in place now? Does it have a porp valve.
It's terrible when guys do the pick & pull, get a part here & another there, instead of buying a donor truck, and having all the parts needed to upgrade their rides.
What engine & tranny does your truck have now?
John
It's terrible when guys do the pick & pull, get a part here & another there, instead of buying a donor truck, and having all the parts needed to upgrade their rides.
What engine & tranny does your truck have now?
John
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Junior User
Joined: Jun 2010
Posts: 94
Likes: 0
Yes there was a booster in it until about an hour ago. Its as suspect as anything else so I pulled it in case I cant determine the appropriate master cylinder that goes with it. Im wondering if its the original booster. It appears to have all the combo valve components.
4.9, 4spd, 4x4.
4.9, 4spd, 4x4.
Posting Guru
Joined: May 2005
Posts: 1,518
Likes: 3
From: Spokane, WA
I typically use Raybestos part# MC36399. It is the front disc/rear drum master cylinder for 73-76 F100's. It will work with or without the booster. Your local parts house should be able to cross that number into their brand if they don't carry Raybestos.
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Junior User
Joined: Jun 2010
Posts: 94
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My buddy tells me that almost any master cylinder that will bolt up, will work. However, the difference on bore size could affect pedal travel and leg strength required to stop. Is that a legitimate concern for a dump run truck or will any that mount up be of comparable bore diameter?
Elder User
Joined: May 2010
Posts: 957
Likes: 3
From: Valley Center, CA
Brakes are an area that I just don't take chances with, and when I did my disc swap not long ago, I went through it with a fine tooth comb.
I would advise that regardless of what you are using the truck for, good brake performance is a must, not just for your own safety, but as well
as a liability to all others on the road with you.
Do it right mate. These parts are pretty cheap new. Why not buy a new booster/master set-up? It's likely that the P/O swapped in the
booster/master from a donor that had been sitting for some time-ie, a wrecking yard. Usually, the masters are drained, but a lot of fluid still remains
in there, and all masters basically go to crap when they sit for a while and need rebuilding or replacement. Sounds to me like it could be the culprit.
He also may not have bench-bled the master, which will never work properly otherwise. Also, have you looked for vacuum leaks with the booster?
Does the truck have a proportioning valve??...it's key, as it divides the different needed fluid volumes between the fr discs and the drums in the rear.
Best,
Jason
I would advise that regardless of what you are using the truck for, good brake performance is a must, not just for your own safety, but as well
as a liability to all others on the road with you.
Do it right mate. These parts are pretty cheap new. Why not buy a new booster/master set-up? It's likely that the P/O swapped in the
booster/master from a donor that had been sitting for some time-ie, a wrecking yard. Usually, the masters are drained, but a lot of fluid still remains
in there, and all masters basically go to crap when they sit for a while and need rebuilding or replacement. Sounds to me like it could be the culprit.
He also may not have bench-bled the master, which will never work properly otherwise. Also, have you looked for vacuum leaks with the booster?
Does the truck have a proportioning valve??...it's key, as it divides the different needed fluid volumes between the fr discs and the drums in the rear.
Best,
Jason
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Logistics Pro
Joined: Feb 2000
Posts: 3,565
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From: Sun River St. George
Brakes
Try Master Power Brakes for advice and parts that you need. Piston for disk brakes will be larger than drum and boosted will be bigger than non boosted. I think a balanced system purchased as a system would be the best and most cost effective way to do this. You can check out evilbay for a nice system for less than 200 bucks.
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
Salvaged setup from a 76 F100 and later replaced the MC purchased at local Napa parts store: p/n 47-36399. Believe same MC, and booster cover period of several Yrs. Kept the 65 brake petal assembly, not sure from description if experiencing simular problem, I found the petal assembly was off by approx. 1-2" so to bring it inline I used aluminum square stock as spacers between the booster bracket and firewall; this was before I was aware of the FTE forum so if experiencing simular problem perhaps other member(s) can provide a another alternative. Suggest replace MC, flush then bleed air from lines, making sure rear brake pads to drum/spindals are within tolerance and no leaks in brake cylinders.Anyhow, had an urge to chime in and add my 
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