Rear Brakes locking

Hi Guys,
Need some help. The brake drum on passengers rear is locking at low speed. You can see in the pic where the wheel literally locked and skidded on the concrete when I park at my house. Most searches here and google point to bad wheel cylinder, a couple posts said gear oil is causing grabbing of the brake shoes. The shoes and seals were dry about 1,000 miles ago when I had the wheel off.

I want to think it's the proportioning valve, but since its only affecting one wheel I would think a bad proportioning valve would affect both simultaneously as there is only one output circuit that that is shared by each drum.

Before I start throwing parts at it, has anyone experienced this exact condition? Thanks.

 

How's the parking brake situation? Cable looks taught in those pics. Functioning properly? Maybe dragging a little? Could just need to adjust the pads on each side by spinning the star gear in there to back them off a little. I would take the wheel and drum off, inspect the drums, pads and hardware. Then if it all checks out, make sure everything is lubed nicely. Make sure the parking brake cables, levers and brackets are all in good order and moving freely. Then re-install drum and re-adjust pad drag. Should be the faintest sound of pad drag on each side when properly adjusted. Wheel should spin freely though. I would also re-bleed the rear starting with the proportioning valve, then passenger side, then driver's side. Not a lot of parts to throw at it. If the pads are good, wheel cylinders maybe. Best of luck and let us know how they go.

 

IF you jack it up when the passenger wheel is dragging can you spin the rear driver wheel or is it also locked?

You're right the proportioning valve sends fluid/pressure equally to both wheels. It only affects front/rear braking proportion.

If, when its locked up, with the car off, does opening the brake bleeder relieve pressure & allow it to turn? .

I had a bad/faulty master cylinder that had symptoms that sound like the same thing as what you're seeing. The fluid wasn't reliably flowing back into the reservoir on the rear circuit. Swapping it fixed everything.

 

I’m guessing your ‘Equalizer’ is frozen which, when in this condition, will Over Adjust the Pass Side Star Adjuster and make the drum too tight on that side. Recco dropping some penetrant on top and follow up with oil. Work the jank out of it. Both those pivots pins should articulate. The Plastic Bushings may be worn as well and need replacing like mine did.

Recco Star Adjust loosen on Pass Side thru the Looky Do Window using Chopstick Technique. Give it a few back offs clicks (make sure parking brake is off when doing). See if this helps.

If not, then wheel cylinder is frozen on that side and you’ll need a rebuild kit (easy and cheap).

 

Thanks Guys. I'm pulling off the wheels this weekend and will update with what I find.

 

Got the drum off today, and as posted in other threads...leaking axle seal. The leak is not appearing at the bottom of the backing plate yet, but I could tell the shoes were dark, damp looking, and there was a very slight wet glaze at the seal. Bummer. There didn't seem to be any up/down play when exercising the axle shaft, but being able to feel a slightly worn bearing seems like voodoo.

Has anyone ever had luck just replacing the axle seals without also pressing on a new bearing at the same time?

 

Why yes! Toyota Seals only.

Check my build post #173

https://www.tundras.com/threads/the...nt-‘build’-a-chronological-story.46816/page-6

 

Wow. Thanks Hand Model. Your post #173 describes my condition almost exactly. My pics aren't great, but you can see where the outer seal is just wet. This is after I wiped it with a paper towel, but even when I first removed the drum, the seal area was not dripping, just glazed with damp brake dust. I suspect the leak is small and happens when the wheel heats up during travel. A little oil seeps out and makes its way down to the drum to then be redistributed when the shoes hit the drum.

As to the axle movement, yes with the wheel off, and pulling vertically on the lug nuts, imperceptible is how I would describe it, but there is something there. No groan or noise is noticeable from the axle so I'm thinking the bearing is ok at 176k. Your post is from June of 2020, have you been back inside the drum to check for leaks since then?

 

Sure thing. Thank you. Oh yeah, I’d constantly monitored for about 3-4k miles afterwards. Best way to check without pulling the drums off is to remove your tire and then peek down throught the ABS Sensor Hole. If you see Oil in there or on your Sensor then it is still leaking. I think some (very little) oil will get by by design, but it shouldn’t be so much that it drips into your drums.

This picture (also from my build page) is what you don’t want to see. Fortunately, I was going through the Driver Axle Debacle at the time and decided to check the Pass side. The picture you see is what I saw, but no oil had made it onto my new Drum Shoes. I quickly bought a Toyota Seal and swapped it in.

Remove tire, and pop off drum, and remove PB Cables. Unscrew 4 Bolts (14mm) on backside and pull Axle out.

You’ll want the Seal as well as the O-Ring (Toyota!). I used a PVC Fitting and Baby Sledge to Tap it in. You’ll want to feel the Mojo before Tapping by doing some Hand Work feeling the install. A little Grease or Oil helps the initial slip in and then some light even taps until she sounds different at bottoming out.

Careful removing this ABS Sensor as its tricky. Take your time pulling and lightly wedging but make sure you are going straight out and up. Do not jank it side to side.

 

I have same problem on my 1990 2nd Gen 4Runner. 12" very low speed tire marks on my driveway after light braking. And its not my new oem brake wheel cyl, (I just replaced) and not shoe problem, or not due to a leak.

 

I mean, this is technically a Tundra forum, but for shits & giggles ... Are you familiar with how to adjust the rod length on your MC/booster, and are you using all-OEM equipment for it, or some store-bought aftermarket BS? If the pushrod length is set a 1/4 - 1/2 turn too long or more, light braking will cause exactly what you're dealing with. Had the same issue with one of my older GM trucks when upgrading to power brakes & steering.

This is not an uncommon problem to find for people who insist on (or have no other choice but) using store-bought non-OEM parts for the MC and/or booster. OEM typically comes pre-adjusted for bolt-on. LAPS-bought 3rd party parts aren't always that way, and you sometimes need to make adjustments.

 

Case in point: https://www.tundras.com/threads/brakes-locking-up-after-replacing-booster.124323/

 

I looked in the 2nd Gen 4Runner forums, but no luck. This is where I saw the exact same symptom of wheel lockup low speed on my passenger side rear wheel after light braking. I only use OEM Toyota or Denso parts, and preferably Japan sourced. I will buy a salvage used Toyota part from a yard out of state before I reluctantly go to a parts store, as in the past I've been burned by re-doing the repair within 2 years or less, paying twice and extra time by buying non OEM, parts store quality and their "lifetime warranty BS". My chassis similar to a T100 and I have the 3VZE and 5sp manual tranny. I have the orange Toyota service manuals i bought in 1995.
I brake fine at normal stopping and 1 month ago bled all wheels the traditional way. I tried reverse bleed from Phoenix Systems. But via my daughter assisting I did a traditional pedal pump bleed and removed all the air, and paid my daughter $$ for her patience and silence. Replacing with a Toyota Japan Cyl 47550-35190 on that passenger side rear did not resolve the issue. The old orig factory 33 year old cyl was a little wet under the rubber. I have the 33 year old orig master cyl. I can't confirm its defective, I "sense" that it is not defective. I have a gut feeling MC its performing, It never gave me squishy pedal. I have all new Dot 3 conventional (never synthetic) fluid.
So by coincidence, I do have a slight whistle sometimes at my brake pedal. So I sourced a used working salvage brake booster from out of state (Colorado)
which I have not installed yet. My goal is to try and install that without disconnecting the brake MC lines.
Any thoughts? I have not adjusted the MC pushrod length but it sounds interesting to me that maybe this is an adjustment issue? It would be nice if it is! Any feedback appreciated.

 

Has any hardware change or maintenance happened between working and not working? i.e. did this start after bleeding, suddenly?

Like, on some vehicles, if you push the pedal all the way to the floor during bleeding, you can blow out seals.

 

This passenger rear wheel lock while lightly braking... while going slow , has been happening for months, prior to me bleeding all 4 wheels and replacing
two rear hydraulic drum brake Cylinders. My brake booster (Orig from factory 1990 Japan) is whistling sometimes when I step on pedal
lightly. I can actually make it gently whistle (not loud) by depressing a certain way. That has been going on for some time. But no squishy brakes.
I have the Toyota organic pads, it stops pretty good. Not afraid I will hit vehicle in front of me...