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I’m chasing a really strange brake issue. Unfortunately, the intermittent nature of my problem makes diagnosis really troublesome.
93 F-250 4WD, 7.5L 5-spd.
Periodically the brakes will just clamp down and not let go.
I’m not talking slight drag, as if the parking brake was left on, I’m talking all four corners, panic-stop levels of braking. Enough to make the big block fight HARD to get the truck moving. Once the truck is moving the brakes start releasing, until the next time they’re applied. The solution when it’s happened has been to get the truck off the road, somewhere safe and start seeing what’s going on.
So far I haven’t found any correlation between driving conditions and the problem occurring. I have noticed that when this situation occurs the brake pedal feels like there’s no vacuum assist. Slightly wooden pedal and then a stall when I try to leave the stop as the brakes are holding on.
Today it happened on two-lanes with 50-mph traffic. The time before I noticed it after exiting the interstate after 25 miles of holding 70.
Up front the pads are new and the rotors are well within spec. Out back everything is new. The rears are adjusted to allow only a bit of drag, but the parking brake pedal locks the truck halfway to the floor.
The flexible brake lines are known to break down internally and cause this issue. The inner liner becomes a one-way check valve which prevents the brake pressure in the calipers from releasing in a timely manner. As a preventative measure replace all of the flexible lines.
Thanks for the fast reply! I have noticed that the front brake lines are starting to slough their outer shielding. That makes total sense in what I’m feeling. It feels like something is preventing the brake pads from retracting.
Great, I’ll get new soft lines on the way and hopefully that will solve the issue.
Thanks for the fast reply! I have noticed that the front brake lines are starting to slough their outer shielding. That makes total sense in what I’m feeling. It feels like something is preventing the brake pads from retracting.
Great, I’ll get new soft lines on the way and hopefully that will solve the issue.
Also lube and clean rub points and slides etc
be safe
Jeremy
is it for sure the fronts dragging to, because if you were to instead move in reverse instead of forward , would you move freely or partially held back yet?
the drums are self energizing and rabs contamination, Ick in brake lines esp at wheeels, residual pressure valve on master may be issued, check your master for blocked cap vent. Check lines ofc you already said you will,
More information… I’ve had this truck for almost a year… it was a well taken care of, one-owner truck. Plenty of documentation as to maintenance, but even so, typically with any older vehicle there’s certain things that always need addressed, brakes high on the list.
I did the typical tuneup stuff, plugs, wires, distributor cap and rotor, change fluids, brake pads, etc.
Even so, brakes have been an issue almost since day one.
The rears were down to the backing plates on both of the rear leading shoes when I pulled the drums off. I replaced everything, one side at a time to be able to reference how things went back together… Unfortunately the PO had not followed the same protocol and got the star adjusters reversed.
At this point I’ve eliminated the auto adjusters in the rear as a way of narrowing down what my issues actually are.
The front soft lines are definitely degrading on the outside and it makes sense they might be coming apart on the inside as well. A small blockage definitely meets the symptoms I’m experiencing.
Last nights Rock Auto order has new front calipers, and all three soft brake lines coming.
My thoughts are that its most likely the fronts are affected by deteriorating brake lines. Chances are the entire braking system has been affected to a degree, so I intend on flushing everything. Despite a fair amount of bleeding when I did the initial brake job, the fluid doesn’t look great, but the master works and I’m not experiencing any of the issues common with a failed/failing master cylinder.
Additionally, the intermittent reality of my troubles makes sense with contamination inside the hydraulics as opposed to a mechanical failure of a component. No fluid loss, better than expected braking performance *MOST* of the time…
At very least, I have a possible solution, which makes dealing with the problems less demoralizing. Rock Auto says parts will be in Tuesday, so hopefully I’ll be able to make a positive update towards the end of next week.
More information… I’ve had this truck for almost a year… it was a well taken care of, one-owner truck. Plenty of documentation as to maintenance, but even so, typically with any older vehicle there’s certain things that always need addressed, brakes high on the list.
I did the typical tuneup stuff, plugs, wires, distributor cap and rotor, change fluids, brake pads, etc.
Even so, brakes have been an issue almost since day one.
The rears were down to the backing plates on both of the rear leading shoes when I pulled the drums off. I replaced everything, one side at a time to be able to reference how things went back together… Unfortunately the PO had not followed the same protocol and got the star adjusters reversed.
At this point I’ve eliminated the auto adjusters in the rear as a way of narrowing down what my issues actually are.
The front soft lines are definitely degrading on the outside and it makes sense they might be coming apart on the inside as well. A small blockage definitely meets the symptoms I’m experiencing.
Last nights Rock Auto order has new front calipers, and all three soft brake lines coming.
My thoughts are that its most likely the fronts are affected by deteriorating brake lines. Chances are the entire braking system has been affected to a degree, so I intend on flushing everything. Despite a fair amount of bleeding when I did the initial brake job, the fluid doesn’t look great, but the master works and I’m not experiencing any of the issues common with a failed/failing master cylinder.
Additionally, the intermittent reality of my troubles makes sense with contamination inside the hydraulics as opposed to a mechanical failure of a component. No fluid loss, better than expected braking performance *MOST* of the time…
At very least, I have a possible solution, which makes dealing with the problems less demoralizing. Rock Auto says parts will be in Tuesday, so hopefully I’ll be able to make a positive update towards the end of next week.
be safe
Jeremy
please enlighten us how you removed the self adjusters from your brake system in the rear
ljke what does it look like now and what did you do
These (and the spring attached to them) are the only part that I actually removed:
Basically I pulled the spring off and pulled this bit off as well.
I will take pictures of what things look like inside the brake drum when my brake parts come in next week.
i would be concerned about the adjuster and the lever that the cable hooks too acting wtihout any proper forces inside, not sure what would happen, but stilll
So far I haven’t had any issues, but I disabled the automatic adjusters with the understanding I would have to manually adjust to compensate for shoe wear and to keep the parking brake working properly. No matter, two days later than they promised, FedEx dropped these off today:
That’s the Raybestos complete auto-adjuster kit, conveniently labeled “L” and “R”…
I’ve had a few previous owner issues with this truck. The original owner is a friend and I know he takes very good care of his stuff, but his dirtbag son attempted to take ownership of the truck at one point and he was apparently the typical nightmare previous owner.
When the temps started dropping in late fall I noticed that the truck took forever to heat up… something clicked and I was proven correct, the kid had taken the thermostat guts out. I took that opportunity to flush the entire cooling system, replace the thermostat, etc.
Heat works great now.
To the brakes, my hypothesis is that the kid mixed up the star adjusters and that was the root of my rear brake issues. Now I’ll KNOW that everything is in the right orientation.
No matter what, I’ve got a lot of brake bleeding gun ahead of me in the next couple days. I’ll be putting new front soft lines and calipers on my brown 3/4-ton and the dual rear wheel swapped 1-ton flatbed is to the point where a solid pedal means we can start road testing.
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