Brake issues.

[4 Running]

I have 1993 V6 4 Runner which is doing my head in.
When I brake there is no pedal and not much stopping power. If I pump it a few times it pumps up and I have plenty of pedal and stopping power.
I have rebuilt the front calipers 10 months ago on pad replacement, replaced the rear wheel cylinders a couple of weeks ago on pad replacement, replaced the master cylinder 2 days ago.
The whole system has new brake fluid through it and has been bled more times than I care to talk about.

So after replacing all of these parts I am still having the same issue. Actually it seems a bit worse after replacing the master cylinder the other day. The master cylinder was bench bled and also bled on the vehicle. Also the whole system was bled after fitting the master cylinder.

What else could it be?
Brake booster????

I am lost.
Any help or advice would be appreciated.

[oldmate]

It sounds like there is still air in the system. Using the brake pedal to bleed often causes air to be drawn back when the pedal is released. The easiest, cheapest but longest method is to gravity bleed as this can't happen. Crack each nipple one at a time and leave it for 5 minutes or so. Keep an eye on the master cylinder level. It shouldn't take more than half the reserve to get fluid from the reserve to the nipple so use that as a guide. Repeat for all bleed points. There might be a proportioning valve above the rear axle that needs doing.

[4 Running]

I just pulled the master cylinder off and set up a better bench bleed kit and made sure no air was left in it by recirculating the fluid back into the reservoir from the outlet holes until no air bubbles were left in the clear tubes. I put it back on and bleed all wheels plus the proportioning valve. I used the gravity method after bleeding the normal way. I have a clear tube which is sealed at the bleeder and submerged in fluid so I can see no air is going back in.

The other day I tried the positive pressure method to bleed it by placing a bike tyre tube over the reservoir and forcing the fluid through. Each time I have bleed the system I have used approx. 250ml of new brake fluid.

I think it might be time for the mechanic.... Thanks oldmate for your reply. But I am out of ideas.

[date]

Possibly your master cylinder main seals are stuffed? By pumping, you are expanding them and they work, but slow application of the pedal allows leakage past the seals.

[patrol man]

I'd have a close look at your front wheel bearing adjustment, and your rear brake adjustment.
If ether of these are out it will produce similar faults to what your describing.

[ae86levin]

Maybe the bike tube method has already covered this but for $20 a bunnings you can make a pretty good bleeder. Check the link below how I bleed mine when I installed rear disks on my Hilux with new master cyclinder.

http://www.outerlimits4x4.com/viewtopic ... 2&t=228173

[904Runa]

I'd have a close look at your front wheel bearing adjustment, and your rear brake adjustment.
If ether of these are out it will produce similar faults to what your describing.

Yep I'd check front bearings. If they are letting the wheel wobble then that pushes the pads back and the pumping brings them back up.

[mico]

I'd have a close look at your front wheel bearing adjustment, and your rear brake adjustment.
If ether of these are out it will produce similar faults to what your describing.

Yep I'd check front bearings. If they are letting the wheel wobble then that pushes the pads back and the pumping brings them back up.

x3, mine had the same issues and tightening the front wheel bearings fixed it.