85 FF / medic

Finished putting v6 calipers, rotors, all new rear brake parts, and a 1 inch bore master. Now the pedal will stay hard while the truck is off or running while still, but if you drive down the road for a very small bit the pedal gets soft and takes a pump or 2 and is fine but losses pressure again. I have bled these things 3 times and no air to be found. Brake booster? Or is there a little stubborn air bubble left in the mix

windedwalrus

did you bleed it at the load valve above the rear axle?

myyota

Get a duel diaphragm brake booster and master cylinder from a 90-95 truck or 4Runner and that should fix your problem. I upgraded to that set up on my 86 4Runner and it works great.

jbtvt

Pressure bled the system?

https://www.yotatech.com/forums/f116...inders-197722/

85 FF / medic

Had no idea you could bleed that thing.... will try it tomorrow.

Will also try pressure bleeding.

The MC is from the Marlin Crawler Kit which I assume is a FJ60 MC. If the above 2 actions dont fix it then I will get an upgraded booster next.

Thanks guys

dropzone

iTrader: (6)

The dual Diaphragm booster is supposed to be an awesome upgrade with the bigger MC.

I can't wait to get mine installed...guys that have done this upgrade claim to be able to lock up all 4 wheels with 37-38's...

waskillywabbit

iTrader: (-1)

Best way to keep air put of your system are vacuum line caps on your brake lines if you remove something.

You've simply got air in your system from not bleeding everything. Did you bench bleed the new MC?

Dual diaphragm is a good upgrade but that's not your issue.

:wabbit2:

85 FF / medic

I did bench bleed the master. My money is on the load valve..... I really had no clue you had to bleed that part.

windedwalrus

E-ROC's yota did the same thing. It had air in the lines at the valve that wouldn't come out when bled from the wheels.

corax

Here's another thought - did you leave your bearing preload too loose? With the tire off the ground, grab the wheel at 12 and 6 o'clock - is there a lot of wiggle? If the pedal feels good sitting still but needs to be pumped up after driving a bit, you might have "pad knock back." This happens on fixed calipers when the rotor slaps the pads as it turns and pushes the piston back in the bore so you have to pump the pedal to take up the slack again. -or- maybe there was some dirt or loose rust between the rotor and hub when you bolted it tight (is there any vibration when you brake?).

I know you're not driving an auto cross, but here's an article that explains knock back a bit better. I would get this on rare occasions in my 4runner, usually after bombing through some asphalt twisties in the desert where I wouldn't touch the brakes for awhile

91diesel

X2 on what Corax said, although I had a slightly different problem. Make sure your rear brakes are properly adjusted all the way out. My rears don't self adjust very well for some reason and I've found my self thinking I need to bleed the brakes (having to pump a couple of times coming to a stop). Really it was having to move the rear shoes enough to start contacting the drums. Once properly adjusted brake pedal felt great and braking performance was much improved.

BigMike

The two we sell are either a 3rd gen Hilux or a FJ80 Landcruiser. The main difference is that the FJ80 has an internal residual valve for the rear brakes, which on a FJ80 are disc.

BigMike

85 FF / medic

After bleeding the system 6 times, I read this. I have a ton of play on both sides. Now I have to muster up the patience to take everything apart again. Speaking of which do you guys have and tricks on how to remove the cone washers on the hub assembly other than beating it with a hammer? Thanks

ccannon222

Using a brass drift, hit the end of the hub studs with a hammer. The cone washers will pop right out.

Chris