Topic: Major Brake Issue

[jtaco1]

Ok, here is a quick background on my situation.  I have a 1988 4 Runner with the FJ80 MC, V6 calipers, a Tacoma rear axle and it is still IFS.  Before this weekend, I had great brakes and little to no pedal travel before the brakes would stop the truck, just like you want.  The other weekend we were wheeling at Rausch Creek when I blew a rear brake hard line due to rust, it finally gave up the ghost.  So we ended up cutting and capping both rear lines to get my brakes back and get off the trail.  We replaced both of the hard lines yesterday and blead the brakes with a power bleader, so there is no air in the system and we did bleed the LSPV as well.  

Now my problem is that when I depress the brake pedal it goes nearly to the floor before the front brakes kick in, the rears are not even doing anything.  We had it up on a lift and spun the tires to verify.  The front brakes are solid and are working great, just have no rear brakes.  When we crack the fittings at the MC and press the pedal the front port send a good amount of fliud like it should, while the rear fitting barely dribbles.

Could there be some air trapped in the MC, since I seem to remember that the resi did go low, but I thought it was the front, not the rear portion due to the hill we were on.  I am going to pull the MC and try to bench bleed it again and re-install it.  Hopefully that fixes it, I really don't want to have to by another MC.

Thoughts???

[*ROKTOY*]

Sounds like a good start. After bleeding the MC bleed the brakes again, make sure you get good flow from the rears if not you may have pushed some rust into the LSVP.

[jtaco1 [OP]]

See thats the wierd thing, when we power bled the rear brakes, we had good stream coming out of the fittings on the rear drums, both sides.  Figured good to go and bam righ tto the floor and where I am now. 

[Jan84HJ60]

You could still have air in the master, sucked in when you blew the line. The easiest way to bleed is to unhook the brake lines from the master, put a big ziplock over it, hold your fingers onto the holes where the brakelines attach (from the outside of the ziplock), and have someone else pump the pedal.
Like this the air will get out, but can't get back in (due to your finger pressure). much easier than bench bleeding, and less messy, as the fluid will be caught in the ziplock.
then just attach the lines and bleed the whole system.

the other possibility is that your rear shoes are way backed off, die you readjust them?

cheers,
J

[jtaco1 [OP]]

I will give that a shot, was also thinking about hooking my bench bleed kit up with the MC in the truck and pump it up that way to get the air out.  Yeah we double checked the rear shoes and they are good to go.  Thanks

[79coyotefrg]

did you get the lines on the LSPV right?  ive never been a fan of the 'gadgets'  for bleeding a system,  ive always either gravity bled or used a buddy and done it the old fashioned way

[jtaco1 [OP]]

Yep, I ended up getting Toyota factory replacement lines and they only go on one way, but if after I bleed the MC again and if it doesn't solve the problem, I will be switching the hard lines, but I am about 99% sure they are correct since they only go one way.  I will be gravity bleeding the system afte the MC work, since I don't have a power bleeder, it was my buddies.

The other thing that leads me to believe there is still some air in the MC is that the rear brake port on the MC doesn't push as much fluid as the front port when they are cracked open.

[All_Set]

Are the wheel cylinder adjusters set properly?  (does your e-brake hold your truck?) 

[jtaco1 [OP]]

Yep, the ebrake hold the truck great and we double checked the adjusters, they were right were they needed to be.

Everything worked great before the rear hardline along the frame rail blew, which reinforces the thought that the MC has air in it.

[jtaco1 [OP]]

So I was able to bleed the MC with it still in the truck and got a great pedal, just like before the line broke, but when I turned the truck on, the pedal goes to the floor.  Bleeding the MC while the truck is running, I cannot get a firm pedal at all.  I think that the MC is shot at this point.  Yes/No??

[OOPS]

You have to take the MC out to bench bleed it, or jack it up until the barrel of the MC is level to get the air out. If not air will be trapped in the front of the MC. After you bleed the MC then bleed as follows:

"...This is from the FSM and it works great..."
1. Drivers side rear
2. Passenger side rear
3. Passenger side front
4. Drivers side front
5. LSPV (Load sensing proportioning valve)

[jtaco1 [OP]]

Yep, did that, the truck was on the trailer and I lowered the front until the MC was level.  What would the difference be if it was out of the truck or not?  I was able to get a firm pedal that I thought was good to go until the truck is running then it went to the floor again.  Brakes are bled as well.

[OOPS]

Yep, did that, the truck was on the trailer and I lowered the front until the MC was level.  What would the difference be if it was out of the truck or not?  I was able to get a firm pedal that I thought was good to go until the truck is running then it went to the floor again.  Brakes are bled as well.

Bad MC or you did not get all the air out.