No brakes with engine running

[MDK231]

Need help. My 94 has no brakes. Hasn't had brakes since I got it.

New brake hoses all around.
New wheel cylinders, shoes, and drums.
New pads, rotors, and calipers.
New Master cylinder (bench bled and rebled lines rr, rl, fl, fr.)

I thought it may have been the rear wheel cylinders were leaking but after replacing everything I've still got no brakes.

I get a good firm pedal that holds pressure as long as the car is off.

When the car is running and you press the pedal, the pedal goes to the floor with little resistance.

Don't think it's the booster as that would cause a stiff pedal if I'm thinking correctly?

Where to next?


Should also mention it is a 94 explorer, 4 wheel abs.
Im at a loss.

 

[Mechrick]

You've got air or travel somewhere.

Some quick things to check:

Calipers on upside down?

Rear shoes adjusted properly?

One way to check for air is to pump the pedal, hold it then remove the master cylinder cap and release it while watching the fluid in the master. If there is air, there will be a small fountain of brake fluid as the air pushes brake fluid back into the master.

You can also clamp off each brake line to isolate each wheel(s), but I don't recommend doing that with brand new brake hoses.

 

[MDK231]

You've got air or travel somewhere.

Some quick things to check:

Calipers on upside down?

Rear shoes adjusted properly?

One way to check for air is to pump the pedal, hold it then remove the master cylinder cap and release it while watching the fluid in the master. If there is air, there will be a small fountain of brake fluid as the air pushes brake fluid back into the master.

You can also clamp off each brake line to isolate each wheel(s), but I don't recommend doing that with brand new brake hoses.

Double checked the calipers. They are right side up.

As far as the drum brakes go I have a small amount of drag when I spin the drum. Is this correct?

I'll have to check this in the master cylinder when I get home.

 

[rusty ol ranger]

Double checked the calipers. They are right side up.

As far as the drum brakes go I have a small amount of drag when I spin the drum. Is this correct?

I'll have to check this in the master cylinder when I get home.

Try pulling the vacuum hose off the booster and plugging the line (pull it off the engine). See if it stiffens up.

I cant remember which truck i had...but it was one...that had a booster fail in this manner.

 

[pjtoledo]

what Rusty said.
also check the rod length/clearance between the booster & master cylinder.

 

[MDK231]

Try pulling the vacuum hose off the booster and plugging the line (pull it off the engine). See if it stiffens up.

I cant remember which truck i had...but it was one...that had a booster fail in this manner.

Thanks. Never thought a booster could fail and cause this. Still need to test by removing the vacuum hose but have a booster on order just in case

 

[MDK231]

what Rusty said.
also check the rod length/clearance between the booster & master cylinder.

How do you check the rod length and clearance?

 

[pjtoledo]

that info is in service manuals, and online. I don't have the answers for a '94.