ahickman

I have been working on my 94 3.0 which failed state inspection owing to the right side brakes not working. Totally stumped after doing the following. Any suggestions or troubleshooting hints would be appreciated.

1. Replaced all brake pads and shoes.
2. Inspected all brake cylinders and calipers for leaks and travel distance.
3. Bled each brake line.

Note: When bleeding the right rear brake, I get plenty of fluid coming through. However, when I put the drum back on and push the brakes down, the caliper does not expand enough to halt the wheel. Almost like there is not enough pressure being built up in the line.

Aaron

thook

Hello Aaron!

Do you have the drum shoes adjusted properly?

abecedarian

have you checked that the pistons in the rear wheel cylinder aren't siezed?
wait... you said right side brakes? neither front nor rear?

ahickman

Yes. I even adjusted them full extent so that they were up against the drum, but still do not push out enought to stop the right sided wheel.

thook

Well, if you're sure on the travel distance of the cylinder pistons/brake shoes, all I can figure is something is hanging up or the drum has too much wear (that seems unlikely, though.

Check and see if the parking brake lever on that side is releasing all the way.

Of course, the MC seems a likely suspect, too.

ahickman

Abe, the inspection report indicates that both FR and RR brakes are problematic. Reading the literature on autoshop101.com indicated that the two were not related in terms of pressure or plumbing. In fact, the front brakes are driven entirely by the master cylinder. The rear two pass from the MC to the ABS actuator and then through the proportioning valve. Correct? If so, what effect could the front right have on the rear right?

Matthew, I should probably measure the inside diameter of the drum to make sure it has not been turned excessively. Thanks for the suggestion.

On another note, the emergency brake is totally shot. I can pull it full extent and the brakes never receive tension. I assume that the cable is overstretched and needs to be replaced? The little bit of adjustment at the midsection did nothing for tension.

abecedarian

okay, I probably shouldn't assume your's is as mine is, but...
both my 88 4runner and 91 p'up are of the diagonally split design where the master cylinder's two outputs each control 1 front and 1 rear cylinder, diagonally. So one port is the front left and right rear and the other is front right and left rear. It's actually a federal requirement for diagonally split braking systems since the late 60's/early 70's... when disc brakes started showing up.

The ABS controller and/or LSPV (load sensing proportioning valve) receive pressure from both the circuits of the master cylinder but combines them into one signal to both rear wheels and modulates that accordingly. So you have to bleed the LSPV and / or ABS system as well before bleeding the rear wheel cylinders.

As for the e-brake, on your truck, it actuates the brake shoes directly and also turns the adjuster within the drum assembly. If the brakes are not adjusted properly, the e-brake won't work either. So, fully depress the brake pedal and repeatedly pull and release the e-brake until it starts to feel tight, i.e. the handle doesn't travel as far when you pull it out, then see how well it holds.

thook

Oooo...ABS. I have a '92 and still don't know anything about that.

A handy tip....the drum shoes can be adjusted also by simply cranking the levers on the backing plates by hand. This way you're not dealing with PB cable tension or lack thereof. You're right there at the rear wheels and can tell when the shoes are adjusted out more easily.

ahickman

Got the time last night to review the plumbing on the Runner. Below is the what I traced. Seems to me that the front pads are totally separate from the rear, excepting that the LSPV monitors the pressure from the front for failsafe measures. Also would think that my problem is totally a mechanical issues at the RR wheel and not plumbing or fluid related. Would you agree?

dirtoyboy

Are you bleeding the LPSV itself?

I cleaned up your diagram a bit for ya

ahickman

Yep. Did that again last night. Only thing left to do is take off the RR drum and measure inside diameter to see if it is overextending the piston reach.