brake master cylinder size

[hf240z]

i upgraded the front brake caliper on my 72 240z with a 4 piston caliper from a 79 or 80 toyota 4 x4. i use the original brake line and a 15/16 brake master cylinder from a 280z. the rotors are newly turned and i put a new brake pads.

i bleed the front and the rear brake. the brake are spongy and have to pump twice for the caliper to actually engage. please help my restless 240z? what did i do wrong? i decided to hire a mechanic to check it. he said that the 4 piston caliper is much to big for the brake master, help???help ???

[2ManyZs]

The M/C is plenty big enough for the 4 piston calipers.

Sounds to me like you have air trapped in the system somewhere, probably in the M/C. If the pedal comes up on the second pump, it's air 99.9% of the time.

One other thing to check while you're at it is the pedal pivot, check to see if it has become oval shaped where the clevis pin mounts into the brake pedal assy. If it has a lot of play, you'll lose pedal travel and that can make a small problem even worse.

[Bambikiller240]

Also, make sure that you have the calipers on the correct side of the vehicle. Bleed screw should be at the TOP, rather than at the bottom of the caliper. If bleed screw is at the bottom, you'd never get the air out.

[Marty Rogan]

I feel your pain. I had one hell of a time bleeding my brakes after putting the conversion on.

Make sure you thoroughly bleed the master cylinder first. Thne move to the right rear, left rear, right front, and then left front. I also had to crank up the rear drums a bit more.

If that doens't do it, try this racer trick that Rick taught me. Once the brakes are bled all around, go to the right front, remove the outer brake pad, open the bleeder screw, then take a pair of lock jaw pliers and force the pistons in. Be careful not to push them past the seals. Put the pad back in and do this to the inner brake pistons. Then repeat on the left front. I was amazed at how much extra air I forced out of the calipers.

Once I got it bled correctly, the brakes are killer!

I also highly recommend installing SpeedBleeders on all 4 corners and the master. It will make your life much easier.

Good luck!

Marty

[hf240z]

where can we get this speedbleeders?

and thanks to everybody for extending your experiences with the conversion.

I feel your pain. I had one hell of a time bleeding my brakes after putting the conversion on.

Make sure you thoroughly bleed the master cylinder first. Thne move to the right rear, left rear, right front, and then left front. I also had to crank up the rear drums a bit more.

If that doens't do it, try this racer trick that Rick taught me. Once the brakes are bled all around, go to the right front, remove the outer brake pad, open the bleeder screw, then take a pair of lock jaw pliers and force the pistons in. Be careful not to push them past the seals. Put the pad back in and do this to the inner brake pistons. Then repeat on the left front. I was amazed at how much extra air I forced out of the calipers.

Once I got it bled correctly, the brakes are killer!

I also highly recommend installing SpeedBleeders on all 4 corners and the master. It will make your life much easier.

Good luck!

Marty

[Bambikiller240]

Most "Speed" shops in my area can get them.

Russell Speed Bleeders

or www.speedbleeder.com

[hf240z]

u r right just as soon as i switch the caliper and bleed it, the break feels really safe. i think it still need more bleeding but i think the stopping power is more than i needed. i will bleed it again when i have nothing to thinker with.

thank your so much guys.

Also, make sure that you have the calipers on the correct side of the vehicle. Bleed screw should be at the TOP, rather than at the bottom of the caliper. If bleed screw is at the bottom, you'd never get the air out.