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F 350 brakes apply by its self

wolf41

5
0
Hi, I own a 1999 Ford F 350 super duty with the 7.3 diesel engine, with ABS but no cruise control.
My problem is that when I first start the truck and run it the brakes (rear ones I think mostly) apply by themselves for about 15 minutes and usualy the problem goes away for a while and then it comes back at random. The problem is getting worse the truck sometimes shakes so much that it feels like it's going to fall apart. I've taken out the fuse for the ABS but the problem doesnt go away. Has anyone had this problem or have any suggestions on what could be causing this problem?
 
surewhynot

surewhynot

Rep whores make me sick
13,843
821
Florida
Does it happen after you have pushed on the brake pedal? My thought are maybe something is sticking.
 
radialarm

radialarm

Clown of Death!
3,770
309
Large Circus Tent, Boyd, TX
Welcome to the site! I agree with Tony on that.( I will probably regret it) There a lot of things to check. Could be a bad connection check al of them carefully.
 
john112deere

john112deere

caffeine junkie
Staff member
10,807
405
central Vermont
Welcome to FTF!

Does that truck have rear discs?

Because I'm forced to park on grass a significant portion of the year, I've had a terrible time with disc brake pads that get rusty on the "nubs" where they slide on the caliper and stick a bit.

If you can reproduce the problem in your driveway, one test to do is get the brakes "stuck" on and then crack the bleeder screw on the wheel that's sticking. That'll tell you if it's a hydraulic issue or mechanical...
 

95F350XL

Master Junk Tech
3,000
49
Belle Mead NJ
Yes it has disks in the back. Ford did away with drums on these year trucks. Your calipers are sticking and then free up and prob stick again. Then from the sticking your rotors have warped.
 

wolf41

5
0
Yes I have disc brakes in back. I forgot to mention that I can actually hear a sort of popping sound coming from the dashboard where the brake pedal shaft comes through the fire wall. This poping sound is heard when the brakes apply by themselves and when they release. Also the brake pedal free travel seems to be not there when the brakes apply themselves.
 
TexasNomad

TexasNomad

FTFS Designated DRINKER!
17,057
676
Half past hell AKA Lubbock Tx
Have you tried an Ouija board?
 
Blue Goose

Blue Goose

16,116
781
Fenton, Missouri
Does your truck's brakes use a engine mounted vacuum pump or does it use hydraulic pressure from the power steering pump to boost the brakes? I had a hydravac (vacuum) boost system on an F600 go bad and free travel in the pedal would decrease and the pedal would get hard as a rock with decreased braking ability. In other words, it developed an internal pressure leak and instead of applying the boost towards the wheel cylinders (drum brakes), the boost back fed towards the master cylinder. I wonder if you have a similar problem using either boosting system?
 
blacksnapon

blacksnapon

Moderator
Staff member
9,461
301
waynesville,mo.
Goose has probably got it, but you might as well look at the mounting bolts for the pedal assembly, booster, master cylinder. There could be a possibility of binding there as well.
 

wolf41

5
0
Hi, my truck has hydro boost which is what I am suspecting, but with a $600.00 price tag for that part I'm a little hesitant to change it just in case that's not the problem. I looked at the master cylinder where it's bolted to the hydro boost and I see a little bit of oil residue. Not enough to determine if it's power steering fluid or brake fluid.
Thanks for the info.
 
Fellro

Fellro

Moderator
Staff member
7,953
361
Iowa County, Iowa
Are they self applying, or do they stick after being applied? I have had many occasions where the brake hoses fail internally, causing the pressure to be retained due to a check valve effect. Otherwise, I would agree it would be the booster failing with a stuck valve or such.
 
blacksnapon

blacksnapon

Moderator
Staff member
9,461
301
waynesville,mo.
What I was referring to, somewhat, I've had a few instances of the firewall cracking where everything mounts. When you hit bumps or whatnot, the brakes can apply. I've welded several.
 

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