Wrench_Slinger

Hello, all!

I just put a new inner seal on my 94 runner's left rear axle, and had to crack the brake line to get the axle off. I had taken the axle off several days before to replace the O-ring, and after getting it all back together, bleeding the brakes and final assembly, everything was fine in the braking department.

Fast forward to yesterday, I remove the axle, replace the old inner seal, and put everything back together exactly the same way as before, including bleeding the brakes, but now I have a spongy pedal.

What gives?

Today, I bled the system starting from right rear, going to left rear, right front and then left front, THEN bleeding at both connections on the master cylinder. I got a few bubbles from both front calipers, but none from anywhere else in the system.

I can't help but think that there is still an errant air bubble somewhere in the system, but I'm at a loss to find it after bleeding the system three times. The brake pedal is spongy, but after pumping it up, it holds brake pressure with no let-off. I checked the booster per the instructions in the service manual, and it checks out. No hissing or loss of brake pressure.

I'm stumped!

Anyone else encounter anything like this?

angrybob

Try this:

1. Push the pedal so that it holds a fairly high pressure.
2. Somehow secure the brake pedal in place (rod/2x4/whatever btwn the pedal and the seat brackets for example)
3. Tap on the calipers and wheel cylinders with a plastic, rubber, or rawhide hammer.
4. Walk away.
5. Tomorrow, tap stuff again
6. Remove the rod and gently release the brake pedal.
7. Check how they feel

More times than not with autos and 100% on motorcycles, this has worked for me to fix 'rogue' air and a soft initial pedal due to it. The high pressure compresses the air bubbles and allows them to move.

Free and easy!

Good luck.
_____________

Wrench_Slinger

I'll try that tomorrow. I'm assuming that it'll be necessary to bleed the system again after "mobilizing" the air bubbles?

wyoming9

iTrader: (1)

You could also have a connection sucking air back into the system. This could be caused by a tiny piece of grit or dirt not allowing the flare fitting to seal 100%

The brake fluid leak is so small it would be very hard to notice

I chased a problem like this for a few weeks a real pain

angrybob

Try without bleeding the brakes first. Then if its still spongy bleed them. Release the pedal slowly.

Wrench_Slinger

Ok, I've tried bleeding the brakes and the fittings on the master cylinder, and I still have a spongy pedal, so now I'm wondering if the ABS system has anything to do with this.

There isn't any mention of the ABS system in the bleeding instructions, but I can't help but think that it would be affected by opening up part of the brake hydraulic system.

I don't see any bleeder fittings on the ABS assembly, and haven't located any instructions about bleeding it.

Anyone got any ideas, or know of any information sources that might help me figure this out?

willyt4r

The Fifth location to Bleed is the LSPV valve.

Wrench_Slinger

Where is that? I don't see it listed in the schematic I have.

Is that the box just inside the fender, just outboard of the master cylinder, with all the looped brake lines going into it?

Wrench_Slinger

Nevermind, I found it-inside passenger side frame rail near rear axle housing. Gonna bleed the LSPV tomorrow morning and see if that doesn't do the trick!

willyt4r

Ar eyou good?

Wrench_Slinger

Got it! Bled the LSPV, which was NOT on the frame rail as I thought, but directly above and behind the chunk housing. After that, I adjusted the parking brake and the truck started behaving itself again.

Now, time to look for a new windshield and some new springs and shocks to get rid of the saggy ass on my Runner!

Thanks for the input, y'all!