On my F350 w/6.9 engine and auto transmission, it seems that my brakes needs more foot pressure to stop the truck. For example, when existing off a highway onto an off ramp to a stop sign, I must push hard to slow the truck down, then at times the binders lock and I slide a little. I'm thinking it's the power booster (?). Thanks

 

I am having the same problem with mine. I was able to reduce the pressure needed to apply them, but it is still not correct. Try pumping the brakes 10 times in a row, fast!!! If you run out of boost pressure before you reach 10 then you will need to replace your vacuum pump/or have the regulator adjusted. Also you need to lubricate the slider pins on the front brakes and make sure there is no rust on the slides.
Also check for:
Loose belt to vacuum pump.
Vacuum leaks.
Hissing noise coming from brake booster.

 

It could be the power booster or it could be the master cylinder. Check the rear brakes and make sure they are adjusted properly before spending any money....Les

 

A quick way to check your vacuum pump is to remove the hose that runs from the pump to the booster, while the engine is running. You should feel the vacuum by putting you hand over the end of the hose if no vacuum the pump is gone. The next check is to shut off the engine with the hose already in the booster, and have someone else apply the brakes while you listen near the booster,If you hear a steady consumption of the vacuum, the internal diaphram may be worn out. Best of luck PHIL

 

 

I had the same problem with my brakes, intermittent power boost. The vacuum reservoir was rusted and was loosing the vacuum. Replacement canister was less than $40. This may not solve your problem but just another suggestion.
Steve, '89 F250 S/C 7.3L C6

 

Normally on these trucks, if the pedal is high and hard or stiff the problem will be one of the following, bad vacuum pump, need to test using a vacuum guage, bad booster or bad check valve on the booster. As for the rear brakes, would not make it have a hard pedal, if the brakes were out of adjustment you would have a very low pedal.

Dave

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