Brake pedal soft, no brakes

Hi,

If it is leaking from the rear, you are correct. The rear seal is bad. As far as the hose you removed from the booster, that was the vacuum assist from the engine. With it disconnected, it is like have the engine off. That's why you were able to build pressure.

As far as removal and replacement, I attached the directions below from the manual. The last two pics are the procedures for bleeding the brakes.

Let me know if this helps. Also, get a different brand of master cylinder to see if the problem goes away.

Take care and let me know what you find.

Joe

If it's a new master cylinders, fully depressing the pedal shouldn't hurt. When they are old, corrosion and dirt get settled in the plunger cylinder and when the plunger hits those points, they can be damaged and cause fluid to bypass the plunger.

I checked the manual to see if there is anything out of the ordinary, and there really isn't. The manual provides directions for manual bleed and pressure bleed. I attached the directions below.

Let me know Also, you indicated there is evidence of a leak. Are you seeing anything leaking?

Take care,

Joe

See pics below.

The proportioning valve is designed to provide equal pressure to the front wheels and the rear wheels. I guess if it's bad, this could happen, but that doesn't explain why the brakes won't release. Are you sure one is dragging and there isn't an issue with unequal pressure to each wheel?

Also, if the pedal won't return, that usually indicates a leak, faulty master cylinder (which I'm sure you don't want to hear) LOL, or air in the system.

Since there are no leaks and you are on the 5th master cylinder, that leaves either air or the proportioning valve that tested bad. Also, were the brake hoses to the calipers replaced?

Let me know.

Joe

Hi,

Yes, there still could be air, but that wouldn't cause the brake to drag. Which way does it pull when you release the brakes? If it pulls left, it is likely related to the left caliper and if it pulls right, the right side.

Try this: Safely lift the front of the vehicle with the wheels off the ground. You can do one side at a time if you want. Start on the side which the vehicle pulls to when you release the brakes.

Have a helper press the brakes several times. Next, have them apply the brakes. The wheel should be locked. Have them release the brakes. Does it turn freely right away or do you have to wait? If you have to wait, do this.

While the brake isn't turning, open the bleeder on the brake caliper. If the wheel releases, my first guess is the rubber brake hose is bad.

What happens is they fail internally. When you apply the brakes, you are strong enough to force fluid through the hose which actuates the caliper. However, when you release the brakes, the caliper isn't strong enough to push the fluid back through in the opposite direction.

Try it and let me know what you find. Also, since the brake pedal still feels soft, make sure none of the rubber hoses are expanding when the brakes are applied.

Let me know what you find or if you have other questions.

Take care,

Joe

If you start it with the parking brake on, does it stay solid?

The reason you are likely getting a better pedal is that the brake pads are engaged via the parking brake. This sounds like a bad wheel cylinder. Have you replaced them?

Here is a link that shows in general how it's done:

https://www.2carpros.com/articles/how-to-replace-a-wheel-cylinder

The pics below are specific to your vehicle.

Let me know what you find. If you haven't checked already, pull one of the boots off the wheel cylinder and see if there is evidence of any leakage.

Joe

See pics below.

Hi,

Let me know what you find. Also, here is a link that shows how in general to replace the brake shoes:

https://www.2carpros.com/articles/how-to-replace-rear-brake-shoes-and-drums

If you look at the attachments below, they are the directions specific to this vehicle. Also, I included the adjustment steps.

I have done many of these, so if you run into trouble, don't be worried about asking.

One other thing. If you find a wheel cylinder that needs to be replaced, before you try removing the brake hose from it, wire brush the connector really well and spray it with penetrating fluid. Allow it to sit for a bit and do it again. Otherwise, chances are the steel line will twist and break.

Take care,

Joe

See pics below.

Hi,

Thank you for the update. I'm glad to hear it's fixed.

Please feel free to come back anytime in the future if you need a question answered or help. You are always welcome here.

Take care,

Joe