Unbalanced brake line pressure?

Matt G

Member
Ok, two potentially unrelated issues on my stock Scout 2 brake system (d44s, disc/drum, oem).

First, the parking brake. It doesn't seem to hold worth beans. I disconnected it for another project 3-4 months ago, and when I reconnected it I think I adjusted it too tight. My rear axle (limited slip) would pop loudly at low speeds, I lost 1 mpg, and it felt gutless towing. I loosened the parking brake cable adjustment and the axle popping dramatically reduced, and I got my 1 mpg back.

So today I pull the rear drums thinking I needed to replace the shoes (hasn't been done in years, and with the e-brake dragging I assumed they'd be toast). Well, the shoes look ok to me: between 0.2" and 0.25" thickness (5mm). See pic (what is the minimum thickness? I couldn't find that info in my shop manual). All of the other brake hardware (springs, cylinders) is of unknown age, but the wheel cylinders aren't leaking. Parking brake still doesn't hold the vehicle in place when in d or r, even at low idle (in reverse you can barely tell it's engaged).

Second, during this whole rear brake ordeal I made a routine inspection of the front disc pads, which had tons of life on them 6 months ago. Well, now one of the pads (driver side outer) is half-eaten away, while the other three front pads are all in great shape thickness-wise. And the driver side front wheel had tons of brake dust on it (unusually so), whereas the passenger side wheel had much less on it. So it looks like over the past few months I'm seeing way too much brake load placed on the front disc brakes (esp front driver side). That's a new condition: the front brakes have worn evenly for years.

Any thoughts? I'm not sure if I'm dealing with two fairly innocuous problems here, or if they're both symptomatic of something else (worn rear brake hardware? Messed up proportioning valve?). Since these are brakes, and this is my dd, I want to make sure it's all fixed.
 

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Sounds like maybe the p.brake is too tite to let it grab all the way an hold?the front thats worn down,May be sticking?caliper.could tear down p.valve,clean it up good an try again or replace it?Jeff,on the pass.,side,could be possible that the rubber brake hose maybe blocking some fluid?they do deteriorate from the inside 1st,and will block fluid flow.they May look good from outside.worth it to pull it apart an blow thru it both way's?Jeff
 
Parking brakes are exactly what they are described as. No vehicle parking brakes can hold a vehicle in drive or reverse.
 
Huh -

in virginia, you fail the annual safety inspection if the following is true:

lis > administrative code > 19vac30-70-90

5. Parking brake will not hold the vehicle stationary with the engine running at slightly accelerated speed with shift lever in drive position for automatic transmission or shift lever in low gear with clutch engaged for standard shift transmission.
 
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Check the 'outside cover' of the cable from inside the cab to where it connects to the wheel cables. If the outside wires of the shield are damaged, the e-brakes loose power because the outside shield maintains the length.
 
Good advice bill, thanks. I'll check that. I did notice the beginning of some fraying on the e-brake cable when I re-connected it, so you May be onto something.

For now I just buttoned everything back up and kept driving. Overall braking seems good - no pulling to either side or any other obvious problems (other than the weak hold on the e-brake). I'll grease the caliper slides and monitor brake pad wear for a while.
 
My rule-of-thumb for non-riveted brake lining thickness minimum: the thickness of the metal backing shoe/pad plate.

I've found that a slight glaze/shine on brake drum and friction lining braking surfaces reduces braking effectiveness. Use some emery cloth on the drums (and then brake cleaner spray on drums and shoes) to remove it.

Most drum brakes don't work as well in reverse because they are self-energizing in the forward direction. Note the difference between primary and secondary brake shoes? Also make sure the shoes *float* (move) easily where they contact the backing plate.

The excessive brake pad wear on the left front could be a caliper that is not sliding easily. It needs to easily slide/float laterally on the caliper bracket. Clean up those contact points on the calipers, brackets, and caliper keys/spings. I use dry graphite on those contact points.

And the tip on the possible compression of the parking brake cable sheathing is good.



"I couldn't fix your brakes, so I made your horn louder..."
 
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