Hello all, this is my first post. I have a '94 7.3 IDI turbo. The motor is fine but the rear drum brakes are pumping up and draging to the point of ruinning new shoes in two days. I have disconnected the ABS to take it out of the equation. Any ideas?

Thanks
Ramblinrich

 

Check the brake hose from the frame. Replace it. It could be it.

 

Who replaced the new shoes.............. they could be installed wrong or be the wrong ones....... give us some more info. Why were they changed in the first place........

 

I changed the shoes, have done my own brakes for 40 years. They are the correct shoes. I replaced them to origanily when I fist bought the truck in Feb. they needed it. The person I bought it from said told me they needed replacing due to his son driving with the E brake on. From then on they have not worked right. Not sure what else to tell you. If you need more please ask .

Thank for the help
Ramblinrich

 

Is the pedal spongy? Does the E brake hold the truck while in drive? If not you need to adjust them some more. I just did mine and thought they were adjusted, tire had a slight drag. But when the E brake was applied with truck running and in drive it wouldn't hold. Cranked on the adjusters enough so E brake holds and they work fine now.

 

I would take one drum off and have someone coherent press and release the pedal slightly. See if things are hanging up. Of course, be careful not to go too far...

Could be a bad hose, sticky wheel cylinders, etc.

What does the fluid look like?...

 

If you do Tbones suggestion.... please put a small retchet strap around the brakes to hold things together............... or the cylinders may pop their internals.

Double check the way you installed the adjuster, it should adjust up when backing up only..... it sounds like it is reversed.

 

Yes, I second both points. Since it's both sides, the adjusters sound more likely than the wheel cylinders both sticking. The previous owner or shop may have got it wrong, and you didn't notice. Is it possible the adjusters are swapped?

If you do go the push the pedal route (a last resort), who is pushing on the pedal is important. It needs to be someone who understands what is going on, or you still may have a mess. Push just enough to make things move and then release.

I guess I should be more careful/thorough when giving advice, even to someone experienced

 

Quick, simple test. Leave it all together. Park on the flat, put it in neutral and push til it rolls a couple feet. Press brakes with truck idling and then jump out and see if it still rolls with the same amount of effort. If it does not roll easily open a bleeder and then try to roll it. If it then rolls easily you can be pretty sure that the problem is your brake hose from frame to axle. It is swollen up inside and of course allowing the pressure from the pedal through but not relaxing the pressure normally so it is keeping pressure on the shoes even after you release the brake pedal.

 

The bleeder part is where I was going. Just remember that you could introduce a small amount of air, so re-bleeding may be necessary.

Another possibility is that the wheel cylinders are used to working in the worn out pad range, and that they stick when trying to return to the new pad position. But in my experience, they just leak when this happens..

I'd change the hose anyway, unless you know it's new.

 

Thanks for the sugges tions, I'll be working on them this afternoon. Will let you know what happens.

Ramblinrich

 

Well it's back together. Thanks to Pete for the info on which shoe is the primary. With the truck up on jack stands and motor idling the wheels spin at about 10 MPH and repeted stop showed no sign of the past problem. the real test will be the drive to an from work monday. Resalts tomorrow.

Ramblinrich

 

Well today went fine. The pedal was soft this morning, but stop OK. Coming home the pedal went hard but the brakes worked fine, no drag or overheating. If there is a change I'll be back for more help. Thanks for all the good advice.

 

1.0 Make sure you got the right shoes, the HD trucks (which includes the diesels) use 3" wide shoes and drums (as measured across the face of the shoe pad) while most of the gassers only use 2.5" wide shoes. This is easily missed and if you use to narrow a shoe the shoe can jam in the drum as 1/2" is too much play.
2.0 Make sure you got all your springs on the correct way.

3.0 Check your E-brake cable, make sure it is not rusted up and jams to the point were when you release the E-brake the shoes don't dis-engage properly. E-brake cables that don't get used all the time (usually a problem on automatics) have a tendency to rust up.

4.0 Consider replacing the hose from the frame to the rear axle. Sometimes the rubber gets so old the hose deteriorates internally and plugs the brakefluid from returning to the master cylinder. Usually this is more of a problem on really old trucks (20+years)

5.0 Have you replaced or re-built your wheel cylinders? The cups get hard over the years and the cylinders generally rust up. Also if somebody drove with the E-Brake and really heated up the drums the rubber cups harden and swell up from the heat causing them to seize in the cylinder. Also the position of the pistons and cups change when you installed new shoes so the cups may now be travelling over a corroded portion of the cylinder again causing possible sticking or seizing.

6.0 If the ABS valve is seized up, disconnecting it alone may not solve your problem. Either replace it (or remove it, not advised unless you know what your are doing and how that will affect your driving)