'93 E350 Motorhome - really frustrating brake problem

[rgnprof]

I have been chasing this issue - literally - for years. I have a "93 Ford E350 Motorhome with front disc and rear drum brakes (RABS). I have had a very spongy, soft pedal and I'm almost positive I've been stopping this coach with only the front brakes. Recently pulled the rear duallys and changed out everything - new drums, hardware, wheel cylinders, shoes...

And I still have the same issue. Today, I've pulled the rear wheels again trying to adjust the brakes. I have spent several hours trying to get them adjusted but I still have no real brake in the rear wheels to speak of. My wife was in the coach, pressing the brakes and I was still able to turn the drums by hand (no tires installed yet) with the brake pedal depressed.

Also, I changed out the master cylinder last year and I have bled the crap out of these brakes!

Any thoughts? My only thought is I still have a hydraulic problem - although the front disc brakes seem to work, OR I still have not gotten these rear shoes adjusted properly to the drums.

Please help! Thanks!
ryan

 

[rockin rockwood]

Check, or just replace the brake lines. The rubber, flexible part will become weak after years and expand and contract under pressure. That's where you're getting the spongy pedal from.

 

[jubileee]

  Could be dump solenoid for RABS stuck open? When you bleed rears, are using two people method? If so, does the brake fluid really squirt out under pressure? Can you hear shoes contacting drums when bleeding?
If you aren't getting fluid pressure and drum action when brakes applied, you could unhook the RABS computer. If you have brake action then, change out computer. If not, may have to change out dump solenoid. (Unlikely)
  I'm not recommending anything, but, system can be bypassed. You on your own there.
    Also, you should be able to adjust brakes up to where you can't turn drum, then back off to slight drag. If you can't, something is installed wrong.

 

[rgnprof]

Well, I had a friend stop by, so we tried to adjust them a bit more - and that seems to have worked (thought I would try the simplest thing first).  Brake lines have been replaced and I've troubleshooted the RABS valve and system for months (haven't eliminated it as a possibility). 

I'm no brake drum expert - done plenty of discs -  but I guess I just couldn't tell if they were adjusted "tight" enough...I'm still concerned that they might be too tight and overheat, but I at least have rear brakes.

Pedal is still soft and spongy though - and makes this noticeable "whooshing" sound when the pedal is depressed...

 

[William52]

Vacuum booster is bad
The noise is the booster leaking.

 

[hedhunter9]

I have heard from several Ford owners that the rear brakes dont have enough stopping power.
One friend of my had a brake booster added for the rear brakes... BIG difference..  He says it stops MUCH better now.

The E350 with 16inch wheels have smaller brakes and there is only so much you can do with them...

Bob

ps...
I have a 94 Coachmen 32' (Chevy workhorse chassis).  I have a good hard brake pedal and the rear brakes still suck..
I can lock the front wheels up,  but never the rear..