Brake pedal soft, no brakes

After bench bleeding a whole nother master cylinder and all my lines ,and verifying nothing else is leaking , were convinced the master cylinders I'm buying are faulty . Following every step exactly , they keep end up leaking at the base of the cylinder , between it and the brake booster . Like the rear cylinder seal gives up immediately upon installation.

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

I've installed 5 master cylinders , they all show signs of leakage . That has to be impossible 5 being a bad one in a row . Still no brakes all the way around . I'm going to try two tests , one I block the master cylinder lines and pump the pedal to see if it will build pressure and hold it . That'll tell me if the master cylinder is bad . then clamp all 4 brake lines in each corner until I find out what area the problem is at. So far , new booster, master cylinder , and front calipers and pads . I tested my proportioning valve with a test light and the test concludes that valve is bad/stuck . I'm about $400.00 in already , so I can't afford to buy one of those right now , I don't think that could stop all pressure in the system anyway . I will update along the way.

I'm bench bleeding the master cylinders at 3/4" " going into the piston" and when we bleed it in the truck I've got a board under the pedal to only let it go like 40% down . So I know we're not blowing them out ...

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.

I've got no leaks anymore , but when bleeding the brake system I can't seem to build full pressure, it feels like I have full pressure with the vehicle off but then with the vehicle on I have about half a pedal .also only provides little braking assistance, and if I try to hit the brakes hard my pedal wants to stick at the floor , then the I have to pull it up by hand . After that happens a couple times the brake system for some reason has to be rebled, it develops air after a few days and then the brakes get weak/light comes on , and the pedal goes to the floor without almost even braking . Another thing is; right after we bleed the front the calipers seem to stick after corners , pulling either left or right for quite a ways . This has all happened about 3 times .

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

I'm not sure about the calipers , it could just be unequal pressure but after I let up from the brakes it pulls one direction or the other for a while . Brake caliper hoses weren't replaced because they're semi decent . Considering they're are no visible leaks , where could air keep entering the system at?

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

All my hoses are in good condition , no expanding /collapsing going on . Put new calipers in and after we were done bleeding I noticed that when my e brake is applied I gain pedal pressure no problem and it holds , but when I take the e brake off , after a few pumps I lose pedal pressure. This is with the vehicle off . What would be causing the lack of pressure with the ebrake being off ? Also , my e brake doesn't work very good, just fyi.

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.

I'll find out in a bit if it stays firm with the brake applied when I start the rig. as for the wheel cylinders, I haven't checked for leakage on them , but I bought 2 yesterday so I'll find out soon . I know that all my hardware needs to be replaced in the drums , springs look extremely deteriorated and the rest is pretty dirty . I bought all the springs yesterday as well . Got to watch a couple videos first since I've never done drum brakes . Will give another update in a few days.

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.

Final update: One last thing I noticed right before I swapped out the last remaining parts "drum hardware kit, shoes, wheel cylinder ". I had perfect pressure with the ebrake on , but would lose pressure once it was released . Thought that was weird . Anyway , I believe the wheel cylinders were the big issue for me. My problem is finally over.

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