I tried to search the forums BUT it keeps kicking me off...So I was wondering if anyone can help me with what I believe is a brake booster problem. When I press down on the brakes, which they work fine, the brake pedal sticks too the floor. I have to put my foot behind the pedal and pull it back up. Any suggestions from anyone would greatly be appreciated. Also if it matters any my truck is 2 wheel drive 77 f150.

 

More than likely the master cylinder.

Unless you have leaking wheel cylinders or calipers.

NO leaks ? see the 1st one

 

ok thanks alot

 

my bronco2 done that,had to change the booster

 

He didn't mentioned engine running or not.
He didn't mention how long the truck has sat..which usually causes M/C's to go bad.

There is a booster test if he wants to verify it before removing anything.


The check valve is start.

 

Yes the engine is running, I have driven the truck alot since I bought it. BUT!! I dont know how long it sat before I bought the truck. The gentleman I bought the truck from got it at an estate sale; where it lived in a barn for many years. Since the late owner's husband died and only used the truck for a farm truck. I have the orginal title and a letter the lady wrote saying that the miles on the truck are all orginal. It says 35 thousand, but Im not sure if that is right. I am currently not using it as a daily driver. It had a few issues that I had to work out before I drive it on a daily basis. I want to get a new exhaust and new front tires. Just bought the rear ones and they cost me $230.00. I am just a little worried that if I have too do this with the brakes now, is their a chance they could fail on me when I need them the most!!!

 

I forgot too mention that none of the brake cylinders are leaking; and im not losing brake fluid at the master cylinder.

 

Does this happen every time you press on the brake ?

If so the Master cylinder seals have probably disintegrated.

Have someone observe the fluid in the MC reservoir while someone else presses on the brake pedal to see if there is a fountain of fluid shoot up.
Don't press hard and fast just an average amount knowing that if you press too hard fluid could spray all over the place.

 

Yes it happens every time I press the brakes. So if there is a "fountain of fluid" then it is definately the master cylinder seals is what your saying???

 

Get a big spring and duct tape it to the back of the brake pedal. -Just kidding... If your problem is the pedal not returning, and your brakeing power is fine, the booster is at fault... UNLESS..... The firewall is rotten with rust. THIS can be your problem. Check for rust where the actuating rod goes through the firewall for heavy rust, or any cracks. Good luck.

 

yes Z1 , If the seals on the piston have deteriorated over time once pushed the pedal will not return because there is no hydraulic back pressure to push the piston back thus the pedal.

Brake fluid absorbs moisture and rusts inside brake components.

Here is the booster test but I still think it is the M/C piston.

 

I had this same problem with my 1977 F150 when I bought it. The previous owner had attached a spring between the dash and the brake pedal and the spring would pull the pedal back up when releasing the brakes. The real problem was the linkage behind the brake booster. On my truck there was a rocker-arm type linkage which the brake pedal pushed on. The rocker-arm then pushed on a rod which applied pressure to the booster. All of the joints in this linkage assembly had become rusty and stiff. I pulled the booster and then cleaned and lubricated the linkage pivot points. After that, I never had another problem with the brake pedal sticking in the down position.

Before you spend alot of money on brake parts, check out that linkage and make sure it moves freely. You will need to unbolt the booster to access the linkage. If I remember correctly, I was able to unbolt the booster from the firewall and move it slightly out of the way so that I could gain access to the linkage. This allowed me to do the job without ever opening the brake fluid system.

 

He is talking about this part.

You can try spraying a penetrating fluid on the mechanism first to maybe confirm it moving freely.

 

thanks for all the info, this helps out alot