First - I've searched and read endless brake threads with similar issues and no resolutions. Now on to my tale of woe flame me if you want, help if you can, at this point anything is better than nothing.

So I've had brake issues since I bought my 89 4runner 22re a year ago. I've replaced master cylinder, calipers, pads, soft lines, wheel cylinder and shoes. I've looked at every hard line and connection with a mirror and light and they all look dry and there's no corrosion. I've gravity bled, pumped and released with helper, vacuum bled, and now pressure bled with a Motive Bleeder.

All this done and my brakes still feel spongy. The pedal travel is within spec, but the brakes just don't have pressure until very low in the travel, near the firewall. This last time after bleeding with the Motive pressure bleeder they felt great at first, then went back down. If I pump them they're fine and right after one stop, if I stop again they are fine. Enough drive between pumps/stopping and they're spongy near and don't really stop until low in the travel; at all times they'll lock up if I jump on them.

I know pedal "feel" is from the shoes, so I've adjusted them with the star adjuster until each rear turns approx. 1-1.5 turns spinning with the wheel on. My e-brake has approx. 7 clicks until it is hard to pull. I've watched the shoes move with the drums off and they're fine.

On to why I think there may be something with the booster: I was so pissed that pressure bleeding didn't work that I decided to ride my brakes to death. While doing this I discovered that while accelerating my pedal is very firm. I know it's obvious that the less vacuum the less the booster works and the harder the pedal is; I've done this with the brakes off to check the booster. However, is it normal that pumping the brakes with the throttle wide open will make the brakes almost too firm? Once I let off the gas the pedal becomes softer all the way back to the miserable spongy feeling at idle, deceleration, or coasting and using the brakes.

So to sum it up - full throttle + pump brakes = ridiculously firm pedal. Less throttle down to coasting + press brakes = spongy feeling. Less throttle down to coasting + pump brakes = normal in my opinion.

Thanks!

 

I just ordered two new Toyota wheel cylinders and will swap out the NAPA cylinders that I put in a few months ago. Everyone is telling me that pedal feel is from the rear brakes. I know my shoes are adjusted correct, but I'm wondering if the wheel cylinders are not fully extending. All the hardware and shoes in there are new and greased properly as well.

I hate to throw parts at it, but can't figure anything else out. I'll also measure the drums while they're off to make sure they're within spec. And of course, another bleeding of the brake system; I've put gallons through this thing.

Any other ideas?

 

Just to follow up with this... it turned out to be a "new" wheel cylinder. Everything looked fine, but when I pulled the boot away sure enough there was fluid build up; not enough to leak, but enough to let air in.

I replaced both wheel cylinders with new Aisin units from Toyota, then used a Motive pressure bleeder to bleed all the air out, and finally adjusted the shoes to get 6-9 clicks on the parking brake. After all that, everything seems to be working great. This is by far the best this truck's brakes have been since I've owned it. The drums may be a little tight, but I'll take that over no pedal at all.

 

Put some more miles on the truck and everything still seems perfect. I finally get to park the big truck and bring the 4runner back to daily driver status. Will know for sure after a week of commuting if it's too good to be true. I just can't believe that I may finally be done with my brake woes.

 

Thanks for the info...!!!

 

yes indeed mine have been doing the same for a month now and i cant fix it! this might work!