I just finished an SAS on my '86 4Runner which included new FJ40 Rotors, rebuilt 1990 V6 calipers and new extended brake lines. Previously I had updated the '86 M/C and vac. booster to ones from a wrecker out of a '91 4Runner.

My issue is that the pedal travels about two-thirds of the way down before I feel any braking. We've bled the system in FSM order a couple of times and the fluid is fresh. After bleeding the pedal feels firm but when I start the motor it goes soft again.

Does this sound like a M/C issue? Would my brakes behave the same way if the M/C was fine but just needed bench bleeding?

Thanks for reading this long-winded post!

Warren

I don't have an answer, but I'm interested to find out what the others say. Over the weekend, I installed steel braided brake lines and Performance Friction front brake pads on my 2000 4Runner. Stopping power is better, but the brake pedal travel is long, and I'd swear that the pedal sinks when I have my foot on it at a stoplight/fast food drive-thru. I've pressure bled the systems a few times. My bud suggested that I bench bleed the master cylinder, which I did not do. I only bled the fluid at each wheel. I also did not bleed the Load Proportioning Valve. I will give these a shot, and I'll let you know if things improve.

Thanks.

I'm hoping that bleeding the M/C does the trick too. I was really looking forward to fantastic brakes after all the mods I've done.

Let me know how it works!

Any other input from the brake experts out there?

Warren

When you install the extension cable and the caliper, did you let the resevoir run out of brake fluid? There may be air trap inside.

We clamped both front brake lines with vise grips but there was some fluid loss. I don't think the reservoir got THAT low but it is possible.

Warren

Hi Ed. I bled he brakes again yesterday using my Motive Products one man pressure bleeder, and it didn't change anything. The car stops fine, but I still have pedal pressure that is lower than I would prefer. The pedal does not come up if I pump the pedal. I cracked the lines at the master cylinder to see if any air bubbles would come out, but none did. Ditto for all four wheels. If the 2k 4Runner has a load proportioning valve, I couldn't find it. The Performance Friction (PF) carbon metallic pads that I installed were the same thickness or possibly thinner than the OEM pads that I replaced. The OEM pads had 40k on them, and I did not have to push the caliper pistons back when installing the PF pads.

I read a story where a guy installed rebuilt calipers on his Jeep, and went through gallons of brake fluid and hundreds of dollars to try to fix his spongy low brake pedal. Turned out that he installed the calipers backwards (Left on the right side, right side on the left). By installing the calipers backwards, the bleeder screw was below the brake line to the caliper, and thre was no way to get air out of the system.

Hmmm... I wouldn't do that, you can damage the brake line. If it is weakened it can expand under pressure, and possibly burst. I usually put saran wrap over the reservoir and put the cap back on, then put the bleeder caps on the disconnected hard line. I lose some fluid but not that much.

If your pedal slowly sinks, its a telltale sign of weak MC seals. If it just goes down too far it could be small air bubbles. The pressure bleeder system is a good way to go, and I have never needed to bench bleed.

We used Vise Grips on the rubber lines that were replaced w/ extended lines. It's funny though, the M/C doesn't seem to slowly go down, the pedal travel is just too far. I haven't done anything else to the brakes while doing the SAS so why would the M/C go south? Doesn't make sense to me. Maybe a pressure bleeder is my answer.


Warren

I am surmising the sequence of what you did from your first post:
1) changed the MC and booster, retaining the stock 1986 calipers, and drove it around a while.
2) SAS and V6 calipers.
3) noticed a difference.
If that is the case, it makes perfect sense. The I4 calipers will engage mucho closer to the top of travel than the V6 calipers. With the V6 units, braking will occur closer to the floor but at the same point as a stock V6 truck. You could confirm that by driving one, and/or play with it by adjusting your pedal. Do not remove all freeplay, though. Brake fluid expands a tad and if you happen to put the MC piston too far into its travel at rest you could have some interesting experiences.

You may have nailed it. My other truck is a V6 '90 4Runner so I'm familiar with the feel. I'll try adjusting the pedal a bit and see if it comes in line. <img src="/forums/images/graemlins/smile.gif" alt="" />