I was driving my '89 F150 yesterday when the brakes started getting worse and worse all of the sudden. I limped home but now I don't know where to look. The peddle goes to the floor. Very little pressure. How do I test my master cylinder? The pads in front are fairly new. 6 mo. or so.

 

rusted brake line is a likely place to look.

 

Thanks, I didn't see any leaks but I will check again.

 

look at brake line beneath the drivers door.

 

If the master cylinder was full and they were still going to the floor.....probly the master cylinder. If it was empty or way down......you have a leak somewhere.....if it isn't an "obvious" leak......it's probly a wheel cylinder. Check the insides of the wheels for wet.

Good Luck

 

I didn't think of that. The masrter cylinder is still full. Sounds like the master cylinder. Any way to check to be sure?

 

I just went out and pumped the brakes with the cap off the reseviour. nothing. No bubbles, no movement of the fluid at all.

 

Did u see any leaks under the truck or puddles on the ground?

 

leave everything hooked up, take the master clyinder off of the brake booster (take off the two nuts and slide it off of the studs) they say that if the part on that side where the piston goes in is wet with brake fluid, the master cylinder is bad.

 

I had the same thing happen to me. All of a sudden lost all braking power.

Turned out that's what happened:

1) The calipers went bad, the rubber part in them

2) Air got into the system

3) Air + brake fluid produced water

4) Water in the system corroded the master cylinder

5) The master cylinder failed to get enough pressure

The brakes would lock up, heat up and fail. Then after cooling off, work again, but temporarily.

I replaced both calipers and master cylinder and basically all of the parts in the system minus the brake lines.

If I had a 89 as a daily driver, I would replace these things pre-emptively.

 

are you talking about the rubber boots around the caliper piston?