wilecoyote

I have a 87 4.9 2WD. I have bled my brakes twice and they are still spongy. While setting at a stoplight with my foot on the brake pedal, the brake pedal will slowly depress to the floor. Is there a different way to bleed the brakes for ABS system than the conventional way of stepping on the brake and opening the bleeder valve?

wde3477

Haven't had a problem bleeding mine. Start at right rear, then left rear, then right front, then left front. Bleed each one until the fluid no longer has air bubbles before going to the next. I find it takes close to two quarts of fluid to get mine where I'm satisfied.

Have you considered that the master cylinder may be faulty? Do you have the rear brakes adjusted properly (the star wheel thing)?

Did you make sure that the master cylinder never went low when bleeding? I know this may seem like a knock on your capabilities, but consider that this site deals with many posters with vastly different experience levels.

Do you close the bleeder valve before allowing the pedal to release? Or, are you using a self-bleeder kit, or having a friend do the pedal work?

You have the right idea - the brake pedal should be rock hard. Just a matter of figuring out why it's not.

wilecoyote

Thanks for your reply. My master cylinder, calipers and pads are two years old. The back brakes are 50 percent on the shoes and they are adjusted. There are no leaks that are visible. I started the bleeding at the right rear, left rear, front right, left front. I have done this twice, using up about two quarts of fluid. Not only did I get the air bubbles out, I also have clean clear fluid. I have my wife stepping on the brakes, she knows not to release the brake pedal until I tighten the bleeder valve and say "release the pedal". After each wheel I check the master cylinder to make sure fluid has not gone dry. The brake pedal is firm after bleeding but after starting the truck the pedal looses it's firmness. Does the Hydraulic Control Unit affect the way the brakes are bled?

transmaster

Go get your self one of these.

http://www.motiveproducts.com/02bleeders.html

I have one and it is one of the best things I have ever purchased to work on braking systems. You should flush out, and replace your brake fluid every few years this pressure bleeder make that job a piece of cake, and you don't have to have somebody pumping the brake pedal you can do the whole job by your self. The one I have is the Power Bleeder Pro which is set up to service American cars. They have adapters to fit other master cylinders such as the old Volkswagen Beetle, BMW etc

wilecoyote

Thanks for the link. I'm all for making it easier.

transmaster

One thing you do not want to install are the bleeders that have the check-***** in them. They work great when you have clean brake fluid but
if there is any contamination and a piece of trash prevents the check ball from closing all of the way and you have a slow leak.

Incidentally it sounds like you have a bad master Cylinder.

NGM

IF you sit with the truck running and your foot on the brake does the pedal slowly sink to the floor?

wilecoyote

Yes. With the engine running and with my foot on the brake, it will slowly sink to the floor.

wde3477

Sounding more like a bad master cylinder to me.

wilecoyote

Thanks wde3477 and transmaster. The master cylinder is only two years old, but with safety being paramount, the master cylinder is coming out. Thanks for your input.