Bleed of brake system...

[Jerry D.]

Brake bleeding…

I did a search and came up with three threads. Followed their ideas, but the results in my effort is zero.

’91 4Runner w/V6 auto, non-ASB...brakes faded to nothing while driving to work, pulled off road and had the truck trailered home. Inspection found the driver’s front caliper was not operating, two pistons stuck in extended position. There had been a slight pull to the right when braking.
Replaced caliper, went to bleed new caliper and got no flow from MC. By that I mean there was some very small amount of brake fluid, less than a teaspoon full.
Bought rebuilt MC, installed and checked brake peddle travel at about ½ inch before MC was contacted.
Removed MC, bench bleed, kept full, installed in truck, took off bleeder tubes, and connected brake lines.
Started bleeding system on truck, using bottle and plastic tube down into liquid in bottle, both rear drums bleed clean with no bubbles.
Brake peddle would not pump up, goes to floor.
Neither front caliper will push fluid out bleed valve, no flow, no pressure, no nothing.
Disconnected MC line to front brakes, did “bench bleed” in truck with tube going back to reservoir on MC, get flow and good volume of fluid movement, little bubbles in fluid, suspect it is due to the plastic bleed not sealing off completely .
Reconnected brake line to front brakes, no flow, no pressure to front brakes.
Tried using vacuum bleed on front calipers, no flow, no pressure.
With MC pumped about 4 times and held to the floor, cracked open brake line to front brakes at MC and get small dribble of fluid.

I have had the MC off a half dozen time, to bench bleed, have done bench bleeding in truck, still cannot get flow or pressure to front calipers. After “bench bleeding” in truck, you can get the front outlet of MC to squirt a stream of brake fluid all over the windshield, don’t ask how that happened.

What may I be missing, doing wrong, holding the wrench upside down, what???

Thanks,
Jerry D.

[corsair23]

Since you are bleeding your brakes on your own you are already way over my level.

However, is it possible that the brake lines from the MC to the calipers are blocked? If you get good flow out of the MC but when you connect up to the lines you get only a dribble seems to me somewhere in the lines there must be blockage.

I apologize in advance if this is not a valid theory

[2ndGenToyotaFan]

You're holding it right, but it's the wrong wrench..... Just kidding.

I would start at the LSPV (the thing connected to the rod the goes down to the axle in the rear) Start bleeding from there, then do the 2 rears and then the 2 front, with the pump the pedal theory. It takes a friend and a piece of clear hoseand a jar, but I've had the best luck with it.

HTH

[Eric_FJ40]

Hey Jerry:

Only thing I can think of is that Corsair is on to something.

Sounds like the line between the MC and the front caliper(s) is clogged. If you have compressed air handy, can you disconnect the lines at both ends and shoot some air into the them and see if they are blocked?

Regarding the LSPV (if the 'Runner has one - my '91 FJ80 does) ...that should be bled last IIRC.

Is it possible that some crud from the hardline came loose and lodged at the junction with the softline? Maybe take all junctions apart to clean and inspect?

[Cube Dweller]

What's odd is that on my 91 runner w/ ABS, the passenger front caliper is fed by the same line that feeds the rear system, they are connected by a Tee that's mounted to the frame rail inside the fenderwell.

And the lines are shorter to the front, so why would it rust only in the front and not in the rear....

You're probably doing this, but have someone pump the brake pedal, hold it in the down position, crack the bleed screw on the passenger front, close the bleed screw then have your helper repeat.

[Bear80]

Well this somewhat mimics my problem so I'll follow up here.

What I've replaced:
Tundra Booster and Tundra MC
Front Rotors
'88-'91 V6 Callipers
Rear wheel cylinders
Steel braided lines f&r
All new pads/shoes
Replaced LSPV from one off a '95-the truck had the cleanest fluid and no rust/moisture in the boot of the valve.
I've even adjusted the rear brakes to the point that they drag and still no difference

Bled the system with a power bleeder at 35psi IN COMBINATION with a pedal pumper helper.


The damn pedal was still mussy and would not lock the front brakes even after I bedded the new rotors and pads. Then in a moment of EXTREME pissed-off-ness and fustration, I put the truck in reverse, floored it to redline and then slamed on the brakes. WTF, the damn front brakes locked and after that the pedal firmed up and the front brakes started working and would lockup. So finally I got the bitch inspected and have been driving it for a week and the brakes work fabulos.

I've power bleed and 2man bled the system probably 50 times since I started having issues and I've lost track of how many GALLONS have passed through.

With the way I locked the front brakes when it was in reverse, I assume the problems stem from the LSPV. However, on my sisters '86 truck and my dad's '87 4runner I replaced both of their MCs, LSPVs and rear cylinders. They BOTH only took one time with the power bleeder and work like new. I'm still going to bleed my truck one or two more times. Also on all 3 trucks, I set the LSPV bar all the way down, all the way up and at the correct hight. Then at each setting, bled all the lines in order, power bleeder at 35psi with the 2man technique.

[2ndGenToyotaFan]

Do you think the arm on the LSPV just needed to be moved around? When the fronts locked up I'm sure the rear got compressed a bit.... Strange though. GLad it's working now

[Bear80]

Oh I should also add that on my truck I had the front and return lines on the LSPV switched. This happened 6yrs ago when I first swaped the lspv(when I first started having brake problems) and I found it last spring when I put the latest valve on. It really made no difference but for others if the valve has ever been replaced you may want to double check that the lines are connected correctly.

[Bear80]

No matter where the arm is set on the LSPV, feeling of the pedal will not change. Only on my 80series I could adjust it slightly and have rear lockup before front lockup, which tells me it is working 100%. I've never got the rear brakes on a mini truck to lock before the front when I adjust the LSPV to do so.

[WristPin]

if you can get the pedal to pump up, have your helper open the problem bleeder. and jam that pedal as hard as you can.
do this a few times and see what happens.

[Bear80]

Originally Posted by WristPin

if you can get the pedal to pump up, have your helper open the problem bleeder. and jam that pedal as hard as you can.
do this a few times and see what happens.

Isn't this the typical way to do the 2man bleed? Pump the pedal a few times until it pumps up, hold, crack a bleeder valve and push the pedal to the floor, then close the valve after a flow of fluid.

[2ndGenToyotaFan]

Originally Posted by Bear80

Isn't this the typical way to do the 2man bleed? Pump the pedal a few times until it pumps up, hold, crack a bleeder valve and push the pedal to the floor, then close the valve after a flow of fluid.

That's the way I have always done it.

[toyrunner]

I made a one man bleeder with of all things, an air line one way valve from an aquarium air pump. It works fine!
Just attach the inlet side to the bleeder with a length of hose and the other end went to a container to catch the fluid. Crack the bleeder, pump a few times close bleeder, replenish the reservoir and move to next wheel, repeat
Danny

[WristPin]

Originally Posted by Bear80

Isn't this the typical way to do the 2man bleed? Pump the pedal a few times until it pumps up, hold, crack a bleeder valve and push the pedal to the floor, then close the valve after a flow of fluid.

yeah it is, but what im saying is smash that pedal down as hard as you can.

[Jerry D.]

Finally got brakes on the 4Runner.

Toyota dealer "pressure bleed" the entire system, then tells me the MC is also bad. I had install three "rebuilt" MC's before taking it to the dealer . Told the Toyota dealer to put on a new MC, and now, the brakes are like new.

Three rebuilt MC's from the local parts house, all bad... Now I own stock in Toyota for what it all cost, but I have a safe 4Runner and it stops. Pays to use new quality parts.

Jerry D.

[2ndGenToyotaFan]

Originally Posted by Jerry D.

Pays to use new quality parts.

Jerry D.

Ding!

Glad you got it all fixed, and you should sue the parts place where you got the bad MC's that's criminal!