Soft Brake issues
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Junior User
Joined: Sep 2007
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Soft Brake issues
I need some help from you Brake guys. 85 F150. We have replaced rear drums, shoes and brake lines, Front pads, disks and brake lines. Also Master cylinder and power boost. Lines were bled as well. Pedal is still soft and travels close to floor to stop truck. Does not appear that calibers are leaking. What else could it be?
Carpenter Local 745
Joined: Apr 2006
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From: on da beach
Does this model have wheel cylinders? If so did you replace them too?
Did you replace the rubber flexlines to the calipers and rear cylinders?
Air in lines? try re- bleeding the lines for starters.
Did you replace the rubber flexlines to the calipers and rear cylinders?
Air in lines? try re- bleeding the lines for starters.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
I know it sounds stupid but try working the rear adjusters up tight till the drums won't turn and see if you have any pedal then.
Of course back them off before you try and move the truck.
Of course back them off before you try and move the truck.
Logistics Pro
Joined: Jan 2007
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From: Martinsburg, WV
Also when you replaced the M/C did you bench bleed it, it mounts on the truck at a slight upward angle and you cannot get all of the air out of it in place, unless you have the back of the truck up high enough to make the M/C level.
Posting Guru
Joined: Jun 2002
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From: Suffolk, VA USA
It's not clear from your post whether you replaced all the steel lines, or just the brake hoses. If you haven't replaced the steel lines, check them for pinhole leaks, especially the line that runs along the inside of the left frame rail to the rear hose. It's really easy for rust to build between the line and frame rail.
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Junior User
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Thanks to all for the responses. The wheel cylinders were replaced with the rear drums so that should not be the problem. I did only replace the brake hoses i will check the steel lines. I assume that if i have a hole i should have some brake fluid or some rust issues. I do like the idea of the rear drums, it is the least expensive!!, The M/C i will have to check on we did not replace it had to have it done due to convience issue.
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Junior User
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It looks like it is something other that the rear shoes. Must be some air in the lines. I noticed that the brake lines from the M/C run into a valve part then out to the rest of the system. I have found that this is Pressure differential value. according to the Hayes repair book a bleeder pin should be pulled out to bleed the front brakes. Has anyone heard of this? I could not find the pin on the valve. All I really want to do is stop the truck!!!
Posting Guru
Joined: Jun 2004
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From: Niceville, FL.
When you replaced the master cylinder and/or power booster did you make sure the pushrod between the two was properly adjusted? If it's too short, the pedal will go nearly to the floor. There should have been instructions on how to adjust the pushrod with the new booster and possibly a little cardboard gauge included.
Moderator
Joined: Jan 2001
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From: Virginia
I have never had to pull the pin to bleed the brakes. I will warn you though, that to fully bleed the rear brakes after everything has been replaced, takes more fluid than the master cylinder will hold. I just did mine several months ago, and ran out of fluid in the master cylinder, and had to start over. I ran the reservoir almost empty, and filled it up again, and a few more times all the air was finally out.
You also might want to park the rear of the truck up hill when bleeding the rear brakes, and park the front up hill when bleeding the front brakes. This helps the air bubbles run to the end of the line.
You also might want to park the rear of the truck up hill when bleeding the rear brakes, and park the front up hill when bleeding the front brakes. This helps the air bubbles run to the end of the line.
New User
Joined: Mar 2008
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I Have Also Been Scraching My Head Over The Same Problem With My 1985 F-350. Changed The Master Cyl. Booster Check Valve, Front Calipers, Brake Pads And Hoses, Also Rear Brakes, Drums, Springs, One Wheel Cyl, The Rear Brake Hose And Both Brake Lines To Each Wheel Cyl. Bled The Heck Out Of The System And Still Have A Soft Pedal. I Have A Shop Manual That Says In The F-150, You Prop The Pin Open On The Proportion Valve, On The F-350, You Push The Pin In To Bleed. I Found Nothing To Push Or Pull On This Valve! I Am At A Total Loss. If You Find Something, Let Me Know, And If I Find Something, I Will Do The Same.
Senior User
Joined: Jun 2007
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I'm glad I'm not the only one with this issue 
I replaced everything you did and still have the same thing {soft pedal}
I just got used to it..it will stop, but feels unsafe at 1st. The other thing I have an issue with is the right rear locks up when I 1st leave in the morning, guess some moisture got in the drums???? After the breaks are used a few times it quits and stops normal...
I replaced everything you did and still have the same thing {soft pedal}
I just got used to it..it will stop, but feels unsafe at 1st. The other thing I have an issue with is the right rear locks up when I 1st leave in the morning, guess some moisture got in the drums???? After the breaks are used a few times it quits and stops normal...
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-ct