Brakes go to floor

[sbhoney]

funny but I would like some real help here if possible. This is getting to be frustrating.

[sbhoney]

Boy it was easier putting a LT1 into this truck than to figure out the brakes. The truck is fast but now I cant stop it. Funny how things work out. I will be sure to let everyone know what the problem is once I get it fixed.

[knucklebuster2]

The booster would not affect the mechanical functioning of the brakes. If it wasn't functioning, you'd only feel a hard pedal requiring more pedal pressure to apply the brakes. The pedal going to the floor usually means air in the lines or a leak. Did you check the actual metal lines going into the master? Sometimes the line splits or cracks from vibration or rusts and although you changed the master, it still leaks. Check especially around the flared end of the line. Did you bench bleed the master before you bolted it to the truck? If not, you forced the air in the master into the lines. I would recheck all the lines and calipers/wheel cylinders(if applicable) for leaks. I doubt two masters in a row were bad. You said there was a leak at the master. Was the leak near one of the lines, or at the back at the booster. Was the internals of the old booster wet when you took the master off? If the line(s) to the master was leaking, it should be wet below it also. This may give you a hint to where the leak is. Good luck!

[Thunderbolt]

I wonder if you could actually have a bad booster.I have never seen anti locks cause this , But I suppose maybe it is possible. Usually antilocks either get super touchy or they don't work. I wish we could help you more, But it has us stumped too.

[sbhoney]

I have norrowed it down to the back brakes aren't working. If I look in the resivior the fluid is only bubbling in the back section. Blead the brakes again and still nothing. I jacked the truck up and the back brakes are not grabbing at all. I can still spin the tires. There is no air left in the lines. I get a steady flow but maybe just not enough pressure for the back brakes to work. Anyone with ideas now?

[broughy84]

Are your wheel cylinders in good shape and not leaking? I would say that they are after all the other checking you have done. I have a Chilton's for this truck....I will check it and post back in a few minutes!

[sbhoney]

Yup. No leaks anywhere.

[broughy84]

OKAY HERE IT IS I AM GOING TO POST IT ALL
Alot of this is common sense,but read it all there may be something that you and your helper have missed...PAY CLOSE ATTENTION TO STEP NUMBER 11. IF YOU HAVE A FAX AND YOU NEED ME TO I CAN FAX YOU THE PAGE THAT COVERS THIS. This is out of Chilton GM Fullsize trucks 1988-1998
Bleeding the ABS system

1. Clean the master cylinder of excess dirt and remove the cylinder cover and diaphragm.

2. Fill the master cylinder to the proper level. Check the fluid level periodically during the beeding process, and replenish it as necessary. Don't allow the master cylinder to run dry or you will have to start over.

3. Before opening the bleeder screws you may want to give them each a shot of penetrating solvent. This will reduce the possibility of breakage when they are unscrewed.

4. Attach a length of vinyl hose to the bleeder screw of the brake to be bled. Insert the other end of the hose into a clear jar half full of clean brake fluid, so that the end of the hose is beneath the fluid. The correct sequence for bleeding is to work from the brake farthest to the master to the one closest. Right rear, left rear, right front, left front.

5. The combination valve must be held open during the bleeding process. A clip, tape, or other similar tool (or an assistant) will hold the metering pin in.

6. Depress and release the barke pedal three to four times to exhaust any residual vacuum.

7. Have an assistant push down on the brake pedal and hold it down. Open the bleeder valve slightly. As the pedal reaches the end of it's travel, close the bleeder screw and release the brake pedal. Repeat until there is no more air in the lines.

8. Repeat this procedure at each of the brakes Remember to check the master cylider level occasionally. Use only fresh fluid to refill the master cylinder, not the stuff bled from the system. (like i said common sense)

9. When the bleeding process is complete refill the master cylinder install the cover and diaphragm and discard the fluid beld from the brake system.

10. Perform 3 function tests with the TECH 1 scan tool. The brake pedal must be firmly applied.

11. ON MODELS WITH REAR WHEEL ABS
a. Refill the jar with clean brake fluid and attach the bleed hose to the bleed valve on the Isolation/Dump valve.

b. Have your assistant slowly depress the brake pedal and hold it. Loosen the bleed valve and expel the air. Tighten the valve and slowly release the pedal.

c. Wait 15 seconds and repeat this procedure. Repeat bleeding the Isolation/Dump valve until all the air is expelled.

12. On Models with 4 wheel ABS repeat step 1-9

[broughy84]

I hope this helps

[sbhoney]

Followed those exact steps when I blead the brakes and nothing. When I press the peddle there is very little travel in it in order to releave the air. You know how when you depress it and then someone cracks the bleeder screw loose it should go down further. Well when I start it goes to within an inch of the floor. Thanks for looking that up though.

[sbhoney]

OK! This is getting to be annoying!! Decided to check something out just for the hell of it. Tried the brakes while the truck wasn't running and had a decent brake pedal. Started the truck and they went to the floor. Turned off the truck again and removed the check valve and had a decent brake pedal. Started the truck without the check valve in place and still had a decent brake pedal until I put the check valve back in, then right to the floor they went. The check valve is working cause I checked it according to troubleshooting. Blew in one side and couldn't blow in the other. Check valve is inserted the right way also since I have checked this in the book and several vehicles. No chance it is in backwards. Any ideas on this one.

[knucklebuster2]

Is it possible the ABS motor is staying on? I have seen this a few times. Do you hear anything under the hood that sounds different...asif it is on or running? Is your ABS light on? If it is on, pull the fuse for the ABS and see how the brakes react. Maybe you should have the car scanned . Maybe the whole problem was the ABS pump and not the master originally. Just a thought......

[whitty]

The power (brake) assist apparently works with vacume from the engine on my 86 Wrangler. I had the same problem but it seemed to be mostly solved by replacing a few vacume hoses. Then again it may be a little different on newer models... but my pedal doesn't have nearly as much travel as it used to. By the way, my brake pedal was fine when the ignition was off, as soon as the truck was started the pedal would sink right to the floor.

[Doug Rodrigues]

SBHONEY,
This is a long-shot, but a logical deduction: Pull off both rear brake drums to inspect the shoes. If the lower spring holding the adjuster in position is broken and the adjuster has fallen out of position you'll never get pressure to the rear brakes and the pedal will go to the floor. Those springs are cheap to buy....about $5 a pair from a brake shop.