My87Runner

OK i will try to explain this the best way i can. I was running just a stock master/booster/drums and calipers and having issues with the pedal going to the floor. I would have to pump them 3 times to get the pedal firm and for the truck to stop. Now i put a v6 master and booster on and having some issues. I have bleed the system RR, LSPV,LR,RF,LF at least 4 times. the brake pedal seems very soft no matter what. Below 5mph if i press the brake all the way down the truck will stop pretty quick but pedal still goes to the floor and is very soft. Now going over 10mph i have to pump the pedal once. The first pump goes straight to the floor while the second will make me stop pretty quick and the pedal feels a little firmer.Anyone know whats going on?

Also not sure if this is normal going to a dual diphram booster but if i am at a stop and pump the brakes the truck will sputter and i can even make it stall if i pump it 3 or 4 times.

All out of ideas this is my DD and really just want this thing to brake.

TnYota87

i might be wrong, but i would try bleeding LR, RR, LSPV, RF, LF.. ?

ioumateo99@yahoo.com

Maybe stupid question but did you check for leaks or air bubbles? Rear drums?

angrybob

New or used booster / master? Aisin (Toyota) or aftermarket? Did you bench bleed the m/c?

Test the booster. A few quick checks should tell you for sure:

1. With the engine off pump the pedal until its completely hard. Start the engine and note two things: did the pedal soften at all? Second, after a say 10 seconds of idle does the pedal feel any better.

2. The second thing to check is if vacuum is getting to the booster. There is a plastic check valve on the vacuum line going from the manifold to the booster side. Carefully wiggle/twist the check valve to momentarily break the seal on the hose on the booster side. If you hear a hissing, you are getting vacuum to the booster. If not, check the engine side (probably not a booster problem). Go from there.

If #1 is NO and #2 is YES on the booster side, you have pretty much confirmed your booster is FUBAR.

Good luck.

My87Runner

When the truck is off without even pumping the pedal it is hard. But as soon as i turn the truck on the pedal goes straight to the floor. Waited 10sec and with it running and no difference. took off the line going to the booster and there was vacuum and the truck died. Another test someone told me to do was take off the booster line and see how the pedal feels. I had to clamp the line close to not stall the engine but i did that and the pedal felt very stiff. Since i have had this truck the pedal has always been to soft.

angrybob

I missed the above. This tells me that you have a torn diaphragm in the booster. You are getting atmospheric pressure from the outside (your cab area where the booster sticks through) into the booster when you apply the brakes. It should be a closed system.

Check valve on the booster end of the hose from the booster to manifold is probably FUBAR.

My87Runner

ok just changed the booster with another v6 one. Now the truck runs normal no matter how much i pump them. Got to do a good test run today

When first starting off in 1st just going 5 to 7mph and i press the pedal to the floor the truck will stop but the pedal goes straight to the floor and there is no pressure on the pedal. Very weird. Now i start driving in 2nd and 3rd and the first press of the brakes the pedal goes to the floor just like when in 1st put it does not come close to stopping barley slows down, guessing its because of the higher speed. I go to pump it and on the second pump the truck will stop. Still very little pressure on the pedal. If i just pump it 3 or 4 times i can get the brakes to have the pressure on the pedal like i think they should have.

Before the v6 stuff i still had to pump the brake to stop. Now after 3 or 4 pumps the brake is alot stronger but it also seems like the pedal takes longer to rise after a pump.

angrybob

New or used master cylinder? Aisin (Toyota) or aftermarket? Did you bench bleed the master cylinder?

My87Runner

used Toyota and i did bench bleed. I have been through 3 boosters and masters in the past and my brakes have always sucked.

angrybob

Press the brake pedal (engine on or off) and hold pressure. If the first stroke goes to the floor pump until you get pressure.
QUESTION: Does the pedal move towards the floor at all?

If your pedal moves to the floor slowly, there is a leak somewhere because its a closed system. Externally you will see brake fluid leaking out of a seal. Internally, I would guess that its your m/c piston seal has a leak. I don't know if a bad LSPV would cause this problem though.

Air in the system would feel spongy, but would hold pressure even though it feels like crap. Imagine stepping on a tennis ball - it would compress but at a point it would firm up.

uglymudder

What's LSPV?

streetlancer

iTrader: (1)

Load sensing proportining valve LSPV

My guess is you still have air in your lines...

wyoming9

iTrader: (1)

Besides getting air in the system or not getting it all out.

With all the changes of parts it is possible to have the system suck in air . With only a very small leak of fluid that would be very hard to notice.

From a bad connection does not take much just a little spec of dirt is enough at times.

Does your E-brake work and do you use it to keep the rear brakes adjusted up once they have been adjusted up by hand to start.

That could have been the cause of your poor pedal since you had the truck or good shoes with drums that are worn out.

I hope you get it figured out.

This is why I hate used parts unless they come off my stuff and I know the history.

lethe

have you adjusted your drums at all? made sure your hubs are tight on the spindles on the front axle? If either of them are loose/ out of adjustment you will have play in the pedal no matter what. I used to have to adjust my drums constantly to make sure i didnt have too much play in the pedal. Once when i was wheeling my brake pedal went to the floor and i had to pump them a few times to stop. After an inspection when i got home one of my hubs were loose on the spindle. I tightened it and never had it happen again. Neither of these things may help you but it wont hurt to check. I havent seen you mention checking them earlier.