Fambugee

Hey guys, first off I have searched but really didn't find exactly what I'm looking for. I just replaced a leaky m/c with a new aisin unit. I bench bled it and bled all 5 points numerous times afterwards. The brakes are still spongy and were before the m/c replacement as well. They seem to lock up fine, but if I'm stopped, I can literally push the brake pedal to the floor or very close to the floor. This can't be normal. Any advice would be much appreciated guys. I have bled dr,pr,pf,df,pv numerous times by having a friend build up pressure, open bleeder, when pedal touches floor i closed bleeder and instructed friend to go ahead and release pedal. I'm not getting anymore air from the bleeders. I'm from Colorado and just drove down to Alabama. I would like to get this fixed before returning. Thanks yotatech gurus! Merry Christmas!

thook

Is the fluid level staying constant?

93toyrunner2

Bleed the master cylinder connections (all of them) several times, then jack up the rear end, get a flat bladed screw driver, and use it to adjust the rear brakes adjuster at the top of the backside of the drum. Turn the adjuster with the screwdriver, hearing the clicks as you get it tighter. If it is not clicking, you are turning it the wrong way.Adjust the rears until you can feel drag on the drum while rotating the tire. Once you have adjusted the rears, start your bleeding process all over again. Refill the reservoir after each wheel bleeding. When you are cracking the bleeder for the last time on each wheel and the LSPV, do not allow the brake pedal to hit the floor. Just crack it open and then quickly close it. This will prevent that little last bit of air getting in.
Make sure that the brake fluid you are using is new, not over a year old. After brake fluid is opened, it will accumulate moisture in it
If this doesn't get it perfect, then the procedure would be to follow each brake line from the master cylinder, along the line, cracking each and every single link all the way to each wheel. It may take some time, and a lot of patience, but this is the only way to get the air out. Once this is done, re-bleed each wheel a couple times, and done.

thook

Cranking the rear brake adjuster levers will accomplish the same thing as with the screwdriver. And, it's a lot easier. Just thought I'd mention that.

Fambugee

thook, the fluid level is consistent. thanks so much for the advice guys, exactly what i was looking for. i will get on this in the next couple of days and let you know how it turned out. i didn't realize these systems were such a pain to get bled properly!!

thook

I didn't either. I can't say I've ever had to go through so much procedure as was suggested. But, if it does the trick, so be it!

4wd4fun

try a hybrid pump it / gravity bleed:
get some silicone hose that fits the bleed screws on the wheels, about 2 feet length and a 1 liter soda bottle and make sure the brake reservoir is full
staring with the left rear (farthest from the mc) loosen the bleeder just enough so fluid starts flowing and attach the hose to it then form a loop UPWARDS so the top of the loop is well above the cylinder and put the other end of the hose in the soda bottle
slowly press and slowly release the brake pedal 4-8 times, or at least enough to nearly empty the reservoir... make sure you don't run the reservoir empty though. any air should get trapped in the high point of the hose if you're pumping slow. if there's air, in the loop pump a little faster so the air gets blown into the bottle- again,make sure the reservoir doesn't get empty. when you don't have air in the loop, tighten the bleed screww, then do the same for the right rear, right front, left front and lsbpv, in that order
it should take about 1.5 pints of brake fluid to completely flush the system and remove any air.

Fambugee

quick update: Well I pulled off the drums and inspected for leaks. I also adjusted the drums to a friction I felt was suitable. Then, I bled the master cylinder and all 5 other points very thoroughly. The result, very slight improvement but nothing to brag about. At this point, the pedal won't hit the floor and it seems to stop as quick as I need it too, just has more travel than desired. There are no leaks in the system so I'm going to take it as is for now and perhaps tinker with it when I return to Colorado. Thanks for the help! Although this still irks me since my '86 pickup still has a much firmer pedal than this (88 4runner).

thook

I wonder if your rear wheel cylinders are travelling freely. Did you take a look at those when you had the drums off?

Fambugee

you know thook i didn't even consider that. i just made sure there were no leaks or obvious damage. could that cause this condition? also, this may be a noob question but i am a noob with drum brakes, can i just operate the brakes with the drum off and visually inspect the cylinder operation?

thook

I'll say possibly. Just depends on how the cylinders are failing, if they're failing. I really only asked if you looked because, often times, a neglected master cylinder (one that's leaking from age and/or poor maintenance) may be accompanied by wheel cylinders in the same state.

Sure. You can operate the brakes with the drums off. However, as much as a PITA it may be, the better idea may be to just take the cylinders apart and have a good look at the condition of the pistons and spring.

Oh, and there's an equalizer on the rear axle that e-brake cable is attached to. Make sure that's moving in it's full range of motion smoothly.