Brake trouble

[ferrarif18]

Ok this is not Buick but need help please. I have K5 blazer just got done changing to 3/4 ton axles and lifting it 4" I bled the brakes and they work but nut as going as I would like. The problem is the peddle goes down 1.5-2" before it grabs. I bled the brakes for a second time with no change. When I push the peddle down it makes a woooosh sound as i push it then stops no vacuum leaks it is like stepping on a ball with good size hole in it. I think it is a bad master cylinder. Please help I want this thing to stop hard and fast.

Jeff

[Rattus]

If you switched to 3/4 ton axles, you have larger wheel cylinders (and calipers if it's disc brakes). The 1/2 ton master cylinder is a smaller bore than the 3/4 master cylinder, so it will travel further to displace the amount of brake fluid necessary to drive the hydraulics out, which means a longer pedal travel.

To fix it:

1. First, make sure that the brakes are adjusted properly. This is another reason for long pedal travel.

2. Then, verify the wheel cylinder sizes. I'm probably right, but probably don't cut it on stopping power.

3. If the wheel cylinders are bigger, you can replace the master cylinder and booster with 3/4 ton units.

4. You also need to check the hydraulic line sizes to make sure 1/2 ton and 3/4 ton are the same. That, I don't know.

5. You also need to replace the proportioninig valve. It will have different valving from the 1/2 ton unit. Note, it may also force you to change your hydraulic tube size.

Good luck, and don't drive behind me until you have it fixed.

[ferrarif18]

Thank you I just order a 1 Ton master cylinder. It bolts on but has a 1 5/16" piston. 1/2 ton is only 1 1/8". the brakes are the same on 1/2 & 3/4 ton up front but for the money $47.00 for new master cylinder and 21 each for new calipers there all going in. Teenagers are going to drive this and i want it stop so fast they think they are going to go through the windshield if they are just thinking of hitting the brakes.

Jeff