Rear brake lockup when wet

[cocoasranger]

I know this problem keeps coming up, but it drives me crazy. I'll run around the block a couple times while dragging and pumping the brakes to heat them up and dry them off, which usually works. But sometimes even then I get into traffic a go into a slide first time I break hard. It's dangerous and embarrassing.

Is there anything else I can do to reduce this problem? It's funny that my rear anti-lock module is new and the abs light comes on then goes out after a couple seconds as it should, but one rear wheel locks up with no sign of pulsation. Isn't this one of the things rear abs is supposed to reduce? Any thoughts appreciated.

 

[19Walt93]

Make sure the rear brakes are in good shape, cylinders free and not leaking ,adjusters free and working, parking brake cables free and adjusted,and shoes good and installed properly-shoes with short linings forward, long linings at the rear. Then seal all the holes in the backing plates with silicone so moisture can't get in. There was a TSB about this years ago that also listed updated shoes so I sealed the backing plates on my 2004 when I did the PDI and ordered the shoes. It never bothered so I never installed the updated shoes. I gave them away after they sat for 14 years, 2 months before I bought another drum brake Ranger.

 

[RonD]

Hold the e-brake release and pump the e-brake pedal until it feels tight and stops coming up higher each time you press it down

This adjusts the Star wheel on the rear brakes making the shoes centered in the drum and just barely rubbing.

This adjustment happens daily if you use the e-brake daily, and also should happen each time you back up and BRAKE to a stop, if you just roll back and then go forward using transmission but no brakes then no adjustment occurs

You can't Over adjust rear brakes, it can only adjust out until shoes are tight to the drum and centered, as they should be

Rear brake lock up can simply be that the rear shoes are not adjusted so when you apply the brakes the shoes can shift and then lock up the drum.

No, the rear wheel ABS sensor can't tell if one wheel locks up, only if both do
Sensor is on the differential ring gear which is still turning if one wheel is still turning

 

[Ranger850]

Sounds like leaky wheel cylinders. Are the rear wheels wet on the inside ?

 

[Uncle Gump]

The problem with the early rabs is that it uses one sensor and tone ring for two rear wheels. Looking into these early systems... I found out there were lawsuits against most auto companies that used a form of it because one wheel in the system could completely lock up but if the other wheel didn't... the rabs (rwal as GM called it) system wouldn't function.

So that's why you're getting one wheel locked up and no rabs. I would look at the wheel that locks up... gonna guess it's probably the same wheel here... look for contamination (gear lube, brake fluid, backing plate grease... ) on the shoes... it will do it pretty much every time.

Ron mentioned adjustment... he is spot on as usual. If you get to far out of adjustment... it will create a low brake pedal for one... but the wheel cylinder pushes on the primary and secondary shoes equally so both shoes leave the anchor pin when braking... which is OK with properly adjusted rear brakes. The problem comes in when the wheel cylinder has to push the shoes to far.... so when the shoes finally contact the drum and self energize... the distance the secondary shoe has to travel to contact the anchor pin was made up with brake fluid that has to be dissipated... the only place it can go is to push harder on the primary shoe... which makes that brake lock up.

 

[mikkelstuff]

I was sick of this too with my 2002 Ranger - just part of the reason I converted to rear disc brakes using Mustang GT rear disc brakes. See:

https://therangerstation.com/forums/showthread.php?t=179079

 

[IIBRONCOS]

After confirming all of the mechanical parts are working properly. I would bypass the RABS module, and install an adjustable proportioning valve for the rear brakes.

 

[cocoasranger]

19Walt93, I'll seal them up good as you suggested. RonD, Great suggestion on adjusting shoes with the e-brake. I was drifting backwards down my driveway in neutral which evidently did nothing. I also did not know that the rabs won't prevent single wheel lock-up. Your explanation and Uncle Gump's expanded comments made the whole concept crystal clear. I'll hold IIBRONCO'S suggestion on a proportioning valve for future action. After all, it worked great on Roadkill's Stubby Bob truck. Thanks all for the many leads.

 

[NbBill]

93 Ranger 10 Inch Backing Plates

I have a 93 Ranger 4wd 4.0 with 10 X 2 1/2 rear brakes. The 3 friction surfaces where the shoes ride are grooved from the wrong shoes years ago. Can't find new backing plates anywhere and have pretty much exhausted the wrecking yard search. Any Ideas??

 

[19Walt93]

File them as flat as you can and lube the contact points with a small dab of never-seize or some kind of heavy grease. Emphasis on SMALL.

 

[kimcrwbr1]

Have you centered the switch between the front and rear brake lines? Put some rags under the master cylinder and have someone push on the brake pedal hard as you loosen the rear brake line out of the master cylinder until the brake light comes on and quickly tighten. Pump the brakes again and hold then loosen the front brake line at the master until the light goes out and quickly tighten. Check the light stays off. Could be a air bubble in the master this procedure bleeds the air out and centers the piston in the metering block.

 

[kimcrwbr1]

Use the slotted hydraulic fitting wrench and get the compression nuts nice and tight.