I'm posting here because this is the most viewed page for this era truck. It's an E350 motorhome, shares brake design and parts with F350 RWD DRW trucks...


The LF brake was down to metal on metal, the RF was fine. I replaced the rotors, brake pads, bearings, races and seals on both sides. Replaced one frozen pin, cleaned and lubed the rest, all are floating nicely. New boots on the pins. New, greased slippers, and the pads are freely moving. Bled the system, and the LF seemed to be hanging up after running the truck and pressing the brake. RF is fine.


Thinking it might be a bad brake hose, I replaced both hoses, and the metal line running between them. Bled it all out, everything seemed OK until I started the engine and pressed the brake, and the LF is hanging up again.


By hanging up, I mean that I can spin the RF rotor pretty easily by hand. I can't move the LF rotor by hand, but it does turn reluctantly if I put a bar between the lug nut studs (not enough force needed to bend the lugs, I was careful of that).


So... the only things not new are the MC and the metal line running from the MC to the LF brake hose. This system doesn't have a valve between the front brake lines, simply uses two fittings on the LF hose.


Is this supposed to be normal? What is the likelihood that this is a bad new (rebuilt) caliper vs. a bad MC, and how do I test the difference? Why/how could the MC cause this?

BTW, I bled the fronts so far. The rears are on a separate circuit and I haven't touched them yet.

Or, is there something else to look at???

Would this likely clear itself after a test drive?

I'm going to tackle the rear drums and rebleed the entire system before looking at the front again. Hopefully, you guys will come up with something that I've missed by then...

Mike

 

You said you replaced one pin on the LF caliper and cleaned and lubed the rest. Did you also clean out the hole you put the new pin into? Usually if the pin is bad enought to be replaced then the holes is corroded up also.

If you replaced the rubber hose and you didn't let the caliper hang down on the new hose then I doubt the hose is bad again, I would take the caliper apart and look for rust, pitting or imperfections on the pistons that may stop them from retracting.

You have a two chamber MC one for front and one for rear, I can't see the chamber only affecting one wheel on the front brakes, if I remember correctly, you only have two lines coming off the MC front and rear, then they split off to the wheels after that, Right? If you have 4 lines coming off the MC then I'd say look at the line for the left brake, the orifice at the MC may be partially plugged not letting the fluid pull back in after braking.

 

Thanks.

The bad pin was actually on the RF. I cleaned the bore, it's nice and smooth (as are the other 3 pins).

I replaced the hoses with the calipers installed, so there's been no twisting or hanging.

Yes, there are only two lines coming off the MC, the front goes to the LF hose, which has an extra fitting for the hard line to the RF hose. I only replaced that hard line because I broke it when removing the LF hose.

If it's likely to be the caliper, I'll return it for a new one before I pull it apart.

It's just an awful coincidence that the LF wore quickly before I started this job, and it seems to be dragging now.

Interestingly, the LF rotor spun freely after bleeding (engine not running). It was only after I started the engine and applied the brake that it's hanging.

Tires are back on, and I can spin it by hand, but the LF is still definitely dragging compared to the RF.

Mike

 

push piston on caliper back a little where wheel spins fine. Apply brakes and release and see if wheel is hung up again. If so get yourself another caliper

 

Yes, did that already too. I'll try another caliper.

Glad I'm doing the rears, that's another whole nightmare.

Mike

 

Got a new caliper, but after doing the rears, I went for a test drive and now have a spongy pedal (worse than before I started)... Time for a shop to look at it.

Mike

 

Sounds like you might just need a good brake system bleeding......

 

I sincerely hope it's that simple.

Mike