Re: 1993 f250 7.3 diesel - hard pedal, hard to stop,
Change the master cylinder on your booster. had the same problem with early 90's ford ranger. The pistons inside the master cylinder are probably worn...... Make sure to bench bleed the new master cylinder....
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Re: 1993 f250 7.3 diesel - hard pedal, hard to stop,
Check front calipers, caliper should "float" to be self centering. If the caliper is stuck only the inside pad is pushing on the rotor instead of the caliper pinching the rotor. You will need to remove the caliper from the assembly, there are usually rubber boots to keep out the dirt and water from the slide pins, they are ofter cracked/broken or missing altogether. You may need a small torch and some rustbuster to get things moving again.
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Booster problems are rare but they do go bad sometimes.
A bad booster generally causes the brake pedal to feel hard to push down, and a lot of pressure on the brake pedal is required to make the car stop.
Rarely, a vacuum brake booster will develop a vacuum leak, which can cause engine performance problems, hissing or whistling noise, as well as requiring increased pressure on the brake pedal to stop.
The first test:
With the vehicle parked, turned OFF, and the parking brake set, pump the brake pedal 5 to 6 times. If the pedal gets harder to push after several times, your booster is probably good.
The second test (To make sure):
After the test above, without making any changes, press and hold the brake pedal with light to moderate pressure.
Now with your foot still on the brake pedal, start the vehicle.
If the booster is good, you will feel the pedal go down when the engine starts.
1: inspect all brake linings first.
no pulling left or right braking?
the car has 100% full manual brakes. if the brake booster fails.
(its only and assist !!! for 50lb small folks)
so does it? it takes more pedal pressure but has 100% full braking.
this is no accident its by design.
make sure none of the brake shoes/pads are soaked in DoT3/4 fluid
or grease or gear oil.
and no brake fluid leaks end to end, this is really #1 on all cars.
look, then look again. even behind and in front of the master cylinder.
look at tires (inside for fluid leaks>)
2: do the booster test. did the vacuum hose to it fall off?
or got pinched, or ?
google brake booster test
if ABS system. get it all checked,
if ABS get the ABS scanned.
if you cant stop correctly,,,,???? , dont drive.
get it fixed.
_______power brake booster, check vacuum to booster and the check valve for brake booster. primary symtom is high hard pedal that requires greater then normal pedal pressure to stop car. testing booster= pump brakes several times with engine off to deplete stored vacuum. turn on engine with pushing slightly on brake pedal. you should be able to feel the pedal fade away a bit, and then become firm. But not hard. if you feel nothing at the pedal when engine starts. Brake booster is not working. Good-day! make sure vacuum is going to booster with engine running. it may just be a bad vacuum line or check valve.
It appears that you have lost the vacuum assistance that works the power booster for the brakes. It is most likely that the vacuum hose that connects from the vacuum pump (which is usually located on the rear of the alternator) to the power booster has gone hard and split where the hose attaches to the metal piping. Check the hose for leaks or splits and re-terminate or replace as necessary. If the hose is OK then the problem could be that the vacuum pump is faulty or the rubber diapraghm inside the power booster has become faulty and developed a leak. A brake specialist would be the best option to sort out these latter problems.
You no longer have vacuum assistence. The brake master cylinder is mounted on the brake booster which uses vacuum generated by the engine to "help" you push the brake pedal. On diesel engines there is normally a vacuum pump on the rear of the alternator which generates this vacuum. On petrol engines the vacuum is generated by the engine itself. Follow the pipe from the booster to the inlet manifold or alternator(diesel) and check for leaks along the whole length and at the joints. Replace the pipe if leaking. If no leaks are found the booster needs replacing. If you have a diesel engine, check the operation of the vacuum pump first before replacing the booster. Make sure the alternator is turning(belt in place) at idle. Disconnect the pipe at the rear of the alternator and hold a piece of paper over the pump opening to check operation. Do not use your hand as this will result in injury even with the engine at idle. Replacing the booster will see you upside down under the dashboard swearing, pleading and begging because that's where the bolts are that hold the booster in place. The master cylinder needs to be removed from the booster before the booster can be pulled from the engine bay.
the problem is caused by either a failed power brake booster vacuum diaphram or a loss of vacuum to the booster, most likely the booster is defective, if this is a diesel then check the enginge driven vacuum pump.
They need to be bleed again all four wheels but your vacuum pump may be bad since diesels don't have vacuum then have to have a pump, check that the booster one way check valve is good if you can blow thew it both ways it's bad, to bleed start from the wheel farthest away from the master cylinder pump the brakes 5 times and hold down then open the bleed valve keep doing this until you get clear fluid out of each wheel once you have done that if it is still mushy and you know you have vacuum re bleed with engine running this will help push more out with power assist. most like the hard brake pedal had to do with no vacuum check out the pump. You may also have to reset the 2 way check valve if you need help with this let me know.
sense its a deisel i would go with the vacume pump, diesels don't put out any or very little vacume, if you don't have vacume than booster won't work hense hard peddel. when you say you let up on peddel and hit it again you got better break tells me it is not getting enought vacume to booster. i would go for the vacume pump.
With no leaks and a little braking action returning by pumping the pedal I would suggest looking into a master cylinder. Low brake fluid level in the master cylinder will cause the brake warning light to illuminate (possibly, also the ABS light).
If the truck has the 7.3L diesel, it will have a vacuum pump which supplies vacuum for all vacuum accessories. I believe if the vacuum level drops below 10 in. of Hg, the brake light will illuminate. If the vacuum pump fails you'll know it as the brake pedal will require quite a bit of effort to effect any braking effort.