Outer Limits 4x4 Board

I did google search and found a few possible problems but i wanted to ask the question for those in the know before i spend more money.

Some background, my brake used to be crap and i got a double diaphragm booster and 1" bore master cylinder off Nemisis on this forum a fair while ago, my brakes have been running this setup for about 4-5 years and have always had a great brake feel and pulled up well.

On a recent trip my brake slowly started to not stop my truck and was getting worse and worse to the point i had to use the handbrake full on downhills to help stop the truck and the pedal went to the floor and was a little spongy.. but no fluid was missing

The master cylinder was weeping over the last 2 odd years so i thought i'd buy a new one.

This was replaced and bled but when the ignition is off the first push of the pedal goes to the floor with a woush of air sound coming out and there after pushing the brake pedal is hard.
When you start the engine and press the pedal it is spongy and bleeds to floor, if you push it in hard and fast it comes up with a bit of pressure and after a second or 2 a woush sound comes out again (hear like air being released) and in one hit the pedal hits the floor.

Now i know the brakes could do with a better bleed but this would not explain the air sound that comes out allowing pedal to move quickly.

Am i up for a new brake booster too?
Problem is i dont know what the double diaphragm booster came off, the new master cylinder came off a VZN130R 4 runner (3.0L V6 i think).

Can i use a brake booster off a 80 series being i am running rear 4 runner drum brakes?

Sorry for alot of reading, Thanks for the help

Bleed brakes again, maybe with engine on, i had this problem once on my 80 and this is what I done.

There could possibly be air in the lines still but was not convinced it is the problem, in the approx 7 years i have had the truck i have blead it the same and it has always been ok.. Not saying it isnt the problem but

Thanks for the reply

I can't help with the problem but was wondering what the difference was with using 4runner rear drums on a hilux? I have a ln106 dual cab and a 4runner chassis with complete rear end sitting in the yard and was wondering if it was worth the swap.

Dave

I removed my leaf spring suspension and installed a 4 runner 5 link coil rear end, so i have 4 runner/surf rear housing and brakes..

Does it make the whooshing noise with the engine running?

If so, the whooshing noise will be a split in the booster diaphragm. You will need a new/reconditioned booster. You should have a firm pedal though, and it will be very hard to push with no vacuum assist. I would put a booster on it first and then try and bleed it again.

Did you bleed the master cylinder before you put it on?

Have you tried bleeding the master cylinder lines first, and then at the wheels (furthest from the master cylinder first)?

yeh but not sure if it is as loud (hard to tell with a noisy engine)

With the motor running its soft and spongy, with the motor off it goes to the floor once and then is hard under foot.

No i didnt bleed it prior to install, didnt know you could. When i put it on i cracked the plug on the underside of cylinder and pumped it till fluid came out then it will push fluid down the lines..

I did change the front callipers with V6 4 runner ones and the front lines drained out, so there is a possibility there is still air in there..

Whats your thoughts
Cheers brad

This will be a 2 person job. NOTE - your wife or girlfreind will complain of a sore leg when finished (and probably during) LOL.

You will need someone to pump the pedal several times (full strokes, slowly). On the last pump, hold the pedal down, and crack one of the master cylinder lines and let it bleed all of the fluid. Tighten the line again (while they still have their foot on the pedal). Repeat this several times, or until all air is gone. Repeat for the other master cylinder lines.

Then you have to do it all over again at each wheel, starting with the furtherest wheel from the master cylinder.

Hope this helps.

Thanks - Adam

thanks for the help, i went to the wreckers and bought a V6 master cylinderand booster (was the same as i had on there) cost me $45, bled the brakes thouroughly and now they are working again as they were..

Guess it was a faulty diaphragm, i hear when the master cylinder leaks, it can damage the seal on the booster and can fail..

Thanks for the help

Good to hear its going again.