Hi everyone looking to get some insight as to what is going on with the brakes on my 1997 F-350. While on a trip to Kansas my brake pedal got hard and had almost no braking power. Limped her home and replaced the vacuum pump and brake booster, figured while I was at it I would do a complete brake job. Replaced the two rear wheel cylinders as well. Bled the entire system with new fluid. Now the pedal goes to the floor. I just replaced the master cylinder and bled the entire system again.....with no results. Any suggestions would be greatly appreciated.

 

Are your rear brakes adjusted correctly?
Did you keep an eye on the fluid level while bleeding making sure it didn't run out putting more air in the system?
Define complete brake job?

 

Did you get a 97 brake booster for your 97? They are better and called zero loss or something like that.

 

Jordanangel, Thank you for your response. I replaced the front pads, the rear shoes, rear wheel cylinders, the vacuum pump and the brake booster. Bled the entire system using, for the first time, a vacuum style bleeder. That seemed to have remedied the Hard pedal issue, but created the issue of the pedal going to the floor. This made me think that somehow the flushing revealed a bad seal in the Master cylinder, So I replaced it yesterday after bench bleeding it. After installation, I bled the entire system again. The rear brakes I adjusted after replacing the wheel cylinders and shoes. I did keep an eye on the fluid level constantly while bleeding the system. Anybody ever have issues with the vacuum style bleeders?

Oldbird1965, Thank You for your response. I ordered the booster through Advanced Auto and it was specified for the truck. I don't know if they sent me the exact one for her , but it seemed to install without any problems.

 

Oldbird1965,
Have you ever had any issues with your RABS hydraulic system? I have got 230,000 on her, and have heard different
/conflicting things about that system. Your truck sounds pretty dialed in.

 

No, no problems with the RABS system. The thing I do with the pedal going to the floor is to gravity bleed. Just let it drip out for awhile. Guys don't always agree with this but it works for me.

 

You do know there is a bleed valve on the on the rabs valve that you have to bleed. If you skip this part you may never get the air out.

 

BuddyBarnes,
Thanks for the input. I did bleed the hydraulic RABS unit. I am really beginning to wonder if it is the vacuum bleeding, first time ever doing it. I think I am going back to the old school method that worked for me for the past fifty years.

 

oldbird1965,
Thanks again for getting back to me. Not a bad idea, I am wondering if it was the vacuum bleeding that wasn't working right. Think I am going back to the old school way that worked for the past fifty years. I had a conversation with a Master Mechanic for Ford this morning and he thinks that it is just air trapped, possibly because of the vacuum bleeder, recommends pressure bleeding it. I need to go find a unit. He doesn't believe that it is the RABS unit either, but gave me suggestions on how to bypass and check the unit. Thanks again

 

I can only think of a few possibilities here; air in the system, rear brakes far out of adjustment or missing the pushrods, drums are off while you're testing, front caliper is bound, or you have a leak. Verify that your rear cylinders aren't on upside down. Upside down cylinders may not be possible on that model, but verify that the bleed nipples are at the top. Verify that the cylinder push rods are in place and the shoes aren't too loose. Even with some air in the system the shoes should move when the pedal is pushed so you can see that everything's in place. When you put the drums on make sure there's not a lot of space between the shoes & drums, they don't have to be so tight you fight them, but should be real close to snug. And make sure the parking brake is off and that the cables/levers at the brakes are retracted and sticking. Make sure the paring brake spreader bar is installed correctly. Make sure your shoes are on right; pretty sure these are self-energizing so the front shoe on each side has a shorter and/or thinner lining than the rear shoe. Make sure your calipers aren't sticking on the sliders. If a caliper flexes when the pedal is pumped it's probably sticking.


When I replace cylinders/calipers/hoses I put a bar or something holding the brake pedal partially depressed, this locks the fluid in the system so it can't drain. After installing the new cylinder/caliper just release the pedal with the new cylinder's bleeder open and gravity takes care of the air. I also do the pedal lock when replacing an ABS unit so at least everything upstream of it stays full. This 'trick' works on clutches and bikes and anything else with a master cylinder, a minute spent preparing saves lots of time & aggravation at the end.

Master cylinder replacement: I've almost completely stopped bench bleeding. I park and/or jack the vehicle at an angle that leaves the inlet ports at the high end of the master and the outlet lines in an upward angle into the master and just bench bleed it on the vehicle using the pedal. All the air will leave through the master leaving the system ready to go. I usually bleed all four corners anyway since brake fluid is usually neglected, but at least there's no trapped air to worry about.

 

And I've vacuum bled successfully many times before learning some of the tricks I posted above. If the master isn't fully bled vacuum won't work, otherwise it should work just like gravity bleeding does, vacuum just speeds it up.

 

'88 E-350,
Thanks for the reply and all the valuable info. I did just jack the truck back up and rechecked the entire rear system, and all is okay. I am going to Re-bleed the system today when my fiance' gets home to help. Hopefully this will take care of everything. Will keep everyone posted. Thanks again.