Problems with my brakes please help
Thread Starter
|
Cross-Country
Joined: Feb 2011
Posts: 87
Likes: 0
From: Yucaipa
Problems with my brakes please help
Hi everyone. I hope I can get the help I need to fix my problem. ok I have a 69 f250 that's had a disc brake swap. The master cylinder was still the drum brake one and the disc brake proportioning valve was not installed. Well anyways my brakes actually worked great. But my power booster was leaking so I replaced it with a new one and the master cylinder. This is where my problems start. I put on the new master cylinder and power booster and my brakes will not work properly now. So I replaced the drum master cylinder with a disc brake one thinking mybe that's the problem and it did not change anything. My symptoms are when you press the pedal its soft about 1/4 of the way then it stops and is very hard like manual brakes and you have to really press on the pedal to get the brakes to work. Any ideas? What can cause this? The new power booster I put on I noticed wasn't as big as the one I took off. Im thinking the power booster is the problem. I bought the disc brake master cylinder for the right year and got the power booster for the 69 f250 with the adjustable rod. All help is appreciated thank you
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
There is an adjustable output rod from the booster to the MC. Sounds like it may be adjusted too short.
If the rod is adjusted too far out, it will keep the MC partially applied, even when you aren't pressing down on the brake pedal and will cause the brakes to drag and can even cause them to lock up.
With the brake pedal at rest, there should be .005"-.010" clearance (free-play) between the tip of the booster output rod and the MC.
If the rod is adjusted too far out, it will keep the MC partially applied, even when you aren't pressing down on the brake pedal and will cause the brakes to drag and can even cause them to lock up.
With the brake pedal at rest, there should be .005"-.010" clearance (free-play) between the tip of the booster output rod and the MC.
Senior User
Joined: Dec 2015
Posts: 143
Likes: 0
This might be a dumb question but I figured I would ask, For starters did you bleed the MC before you put back on the truck? and 2nd if you pump the brakes do the brakes get hard if they do then I would think your power booster is doing its job?
Thread Starter
|
Cross-Country
Joined: Feb 2011
Posts: 87
Likes: 0
From: Yucaipa
MC was blead. I beed the brakes multiple times to see if thats the problem. I did some research and found that the power booster i bought is for drum brakes. I found that the disc brake set ups take a different one and is bigger. Like the one i took off and replaced. But the problem is the only one i can find that specifies for disc brakes doesn't have the adjustable rod. Would it work?
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
List the parts store you got the booster/MC from and the parts store numbers for these items.
I have an idea what booster you have but without knowing for sure, it's hard to know for certain which one it is.
There are also various bore diameters on the MCs (1.00", 1-1/16" and 1-1/4" diameters for example). A very large MC bore can make it difficult to put sufficient force on the brake pedal to actuate the brakes.
If the tip of the booster output rod is adjusted too short, you will have an excessive amount of forward brake pedal travel before it begins pushing the MC pistons in.
How to adjust the booster output rod to the MC. (PDF file download).
http://www.google.com/url?sa=t&sourc...JFXor3XOvX1rCA
Another thing that can cause a long pedal travel is if the rear brake shoes are not adjusted out. Lift the back wheels off the ground, tighten up the brake adjusters until you can no longer turn the wheels/tires by hand then back the adjusters off 10 clicks.
Residual air in the brake system will also make the pedal mushy or have a long travel.
I have an idea what booster you have but without knowing for sure, it's hard to know for certain which one it is.
There are also various bore diameters on the MCs (1.00", 1-1/16" and 1-1/4" diameters for example). A very large MC bore can make it difficult to put sufficient force on the brake pedal to actuate the brakes.
If the tip of the booster output rod is adjusted too short, you will have an excessive amount of forward brake pedal travel before it begins pushing the MC pistons in.
How to adjust the booster output rod to the MC. (PDF file download).
http://www.google.com/url?sa=t&sourc...JFXor3XOvX1rCA
Another thing that can cause a long pedal travel is if the rear brake shoes are not adjusted out. Lift the back wheels off the ground, tighten up the brake adjusters until you can no longer turn the wheels/tires by hand then back the adjusters off 10 clicks.
Residual air in the brake system will also make the pedal mushy or have a long travel.
Thread Starter
|
Cross-Country
Joined: Feb 2011
Posts: 87
Likes: 0
From: Yucaipa
I purchased the parts from O'Reilly auto parts. The booster i bought Part Number: 54-73515 and the master cylinderPart Number: 10-1529. These were ordered looking up a 1969 f250. The booster i think i will need is under a 1969 ford f350 Part Number: 54-73112
Trending Topics
Lead Driver
Joined: Apr 2011
Posts: 6,399
Likes: 40
From: El Dorado, Arkansas
The MC you have has a HUGE bore diameter --1-1/4" diameter. If you had a dual diaphragm brake booster, the one you have now is a single diaphragm unit. It doesn't have enough oomph to actuate that large of a MC bore.
If you stay with the single diaphragm booster, a 1.00" bore MC will be more agreeable with that booster. The MC for this would be NMC1388 (O'Reilly number).
The 54-73112 booster number is for a dual diaphragm unit. It's a much more powerful booster than the single diaphragm booster (nearly TWICE the surface area). --this is also the same exact dual diaphragm booster that I have on my '69 F100 --mine came from a '75 F350. (except I'm running a modern '95 Ford Explorer 1-1/16" bore MC and not a conventional cast iron MC).
If you go back to a dual diaphragm booster and plan to run a cast iron MC, I would recommend a (new) 1-1/16" bore MC for a '79 F250, O'Reilly part number NMC1676 ($35.99).
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Thread Starter
|
Cross-Country
Joined: Feb 2011
Posts: 87
Likes: 0
From: Yucaipa
First off, the 10-1529 MC is a remanufactured unit. I NEVER recommend a remanufactured MC. They most often don't last long before you will be changing it out again. It's ALWAYs best to buy brand new MCs.
The MC you have has a HUGE bore diameter --1-1/4" diameter. If you had a dual diaphragm brake booster, the one you have now is a single diaphragm unit. It doesn't have enough oomph to actuate that large of a MC bore.
If you stay with the single diaphragm booster, a 1.00" bore MC will be more agreeable with that booster. The MC for this would be NMC1388 (O'Reilly number).
The 54-73112 booster number is for a dual diaphragm unit. It's a much more powerful booster than the single diaphragm booster (nearly TWICE the surface area). --this is also the same exact dual diaphragm booster that I have on my '69 F100 --mine came from a '75 F350. (except I'm running a modern '95 Ford Explorer 1-1/16" bore MC and not a conventional cast iron MC).
If you go back to a dual diaphragm booster and plan to run a cast iron MC, I would recommend a (new) 1-1/16" bore MC for a '79 F250, O'Reilly part number NMC1676 ($35.99).
The MC you have has a HUGE bore diameter --1-1/4" diameter. If you had a dual diaphragm brake booster, the one you have now is a single diaphragm unit. It doesn't have enough oomph to actuate that large of a MC bore.
If you stay with the single diaphragm booster, a 1.00" bore MC will be more agreeable with that booster. The MC for this would be NMC1388 (O'Reilly number).
The 54-73112 booster number is for a dual diaphragm unit. It's a much more powerful booster than the single diaphragm booster (nearly TWICE the surface area). --this is also the same exact dual diaphragm booster that I have on my '69 F100 --mine came from a '75 F350. (except I'm running a modern '95 Ford Explorer 1-1/16" bore MC and not a conventional cast iron MC).
If you go back to a dual diaphragm booster and plan to run a cast iron MC, I would recommend a (new) 1-1/16" bore MC for a '79 F250, O'Reilly part number NMC1676 ($35.99).
Senior User
Joined: Jun 2006
Posts: 204
Likes: 2
From: Cypress
Ultraranger is the man on this. He helped me get my 68 F100 dialed in. Disc brakes were already on when I bought my truck but they kept the drum prop valve or brake junction. Once I changed to the disc/drum prop valve they were perfect.
Thread
Thread Starter
Forum
Replies
Last Post
Chef Tim
1961 - 1966 F-100 & Larger F-Series Trucks
10
Jul 23, 2015 01:09 PM
rc1099
1967 - 1972 F-100 & Larger F-Series Trucks
4
Sep 3, 2009 12:11 AM
coletrain777
1967 - 1972 F-100 & Larger F-Series Trucks
5
Sep 21, 2007 08:27 PM