Spongey Brakes

[BDS_237]

01 XLS - The brakes have always been softer than any other car I have owned, but over the last 6 months they have gotten softer in the pedal. The thing nearly goes all the way to the floor. This past Wednesday I bled the brake lines and the master cylinder with no results. I've also recently put on new brake pads, rotors, and hardware.

Is this simply a pedal adjustment, warped rotors possibly (no noticeable flux in pedal), or possibly seized calipers? It stops O.K., but I did notice with a full car of people it takes longer than it feels like it should and requires much more pressure on the pedal than any other car.

Should I be looking at rebuilding/Replacing the calipers at the wheels next?

BTW - it is still squeaking on occasion even after replacing all of this.

Thanks.

[roady94]

- Just been through this with my '01 XLS. Assuming you did a proper job of bleeding the brake system and checking the condition of the flexible hoses then;

First thing to check for is a leak. Did you top off the MC after bleeding? Is the level stable? If no change in level, move on to next option.

Is there an internal MC leak? If the seals got scuffed during extended travel before new pads, or during bleeding, then brake fluid will bypass the seals and allow the plunger to extend, while only applying minimal pressure to pads. This will only get worse. To check, disconnect the two lines coming out of the MC. Plug the holes. Pedal should be rock solid, with or without the engine running. If pedal is not solid, you have an internal MC leak. Replacing the MC is an easy job. DO NOT skip the bench-bleed procedure before installing it into the car.

If the pedal is rock solid with the holes plugged, you have air somewhere in the system. More on this if necessary.

SIDE NOTE - is car running proper? Do you have a CEL?

Report back if needed.

[BDS_237]

Good input, thank you. I will check the MC within the next few days. What did you use to plug the two holes where the lines connect? Anything you can recommend for that?

[roady94]

Originally Posted by BDS_237

. . . What did you use to plug the two holes where the lines connect? Anything you can recommend for that?

- I have plugs. If your local parts house does not have plugs, purchase the smallest length of steel brake line they have (fittings included). Cut the steel tubing with 1.5" extending beyond each of the fittings. Flatten the ends of the tubing with a hammer. Remove the lines from the MC and screw these into place. If you flatten with care they won't leak for this test.

[trinity03]

very nice info. roady... thanks.

[BDS_237]

Yeah, thanks alot for that Roady. That will be a great help.

[05DCLB]

Most likely the caliper slides are seized on rear calipers and possibly the pads are seized in brackets. The fronts hold up a little better but our winters are real rough on brakes. Unless someone opened up system air getting in is rare.

[roady94]

Originally Posted by 05DCLB

Most likely the caliper slides are seized on rear calipers and possibly the pads are seized in brackets.

- Wow! Please explain how you arrive at this as the 'most likely' cause.

[05DCLB]

Work on them everyday.

[roady94]

Originally Posted by 05DCLB

Work on them everyday.

- Uhmm, okay . . . but far from a thorough diagnosis or explanation. There are plenty of folks out there working on Toyotas every day, and making bad calls. Even in the dealerships.

Please differentiate yourself from those hackers and explain how increasingly spongy brake pedal and increasing pedal travel (almost to floor) is 'most likely' caused by seized rear caliper slides or rear pads seized in the brackets.

[05DCLB]

I am just telling you what we see on a daily basis, common sense would seem that seized brakes ft or rear would make pedal hard but opposite is true. I work about 10 miles from Streetsboro so I know the winters {road salt} pretty well. I know almost anything is possible but cannot remember the last time I replaced a master cyl.

[roady94]

Originally Posted by 05DCLB

. . . common sense would seem that seized brakes ft or rear would make pedal hard but opposite is true . . .

- Thanks for a more complete response. The basic function of a hydraulic braking system is one of the easiest to diagnose on a vehicle, even with power assist, even with ABS. I agree with you about the "common sense" indication. I disagree with your assertion that the "opposite is true".

If all other elements of the system are functioning properly, there is no way that seized brakes alone (front, rear, or both) will cause sponginess or excessive travel in the pedal. No exceptions. For the opposite to be true would defy the laws of physics (compressing good brake fluid).

Don't get distracted by the fact that salt is used on the roads of Ohio. Don't dismiss a bad MC because you can't remember needing to change one.

I guarantee that when the solution to this problem is finally determined, it will be something simple and fall under the heading of 'common sense'.

My first guess is that the system has still not been bled thoroughly. Second guess is the MC. Providing there are no leaks or ballooning hoses, these are the only options.

Also, you stated earlier that "Unless someone opened up the system air getting in is rare. " This is also untrue. Some auto manufacturers (GM for one) place a rubber bladder in the MC to avoid air interacting with the brake fluid. Toyota does not do this. The Gen2 Avalon/Camry system is always open. There is air in the MC reservoir at all times, and more air enters as the pads wear and fluid is moved into the lines to compensate. Here is a good explanation of how the process advances.

Whenever I'm faced with a diagnostic challenge, I constantly remind myself of the following;

• When all else fails, look for the obvious.
• The laws of physics will not be denied.
• There is no such thing as magic.

Hope this helps.

[05DCLB]

I'm not dismissing a bad anything but before you send someone on a wild goose chase I thought maybe the basics should be checked first. 99 times out of 100 seized caliper slides,seized in place pads ft or rear are the problem. Dont confuse air in master cylinder reservoir with the rest of system. Maybe you could use a 4th item on your diagnostically challenged list, remove your head from your can. Hope this helps.

[roady94]

Originally Posted by 05DCLB

. . . 99 times out of 100 seized caliper slides,seized in place pads ft or rear are the problem. Dont confuse air in master cylinder reservoir with the rest of system. Maybe you could use a 4th item on your diagnostically challenged list, remove your head from your can . . .

- Woah. I can see this effort is most likely futile, but I'll respond.

Regarding seized caliper slides or seized pads causing spongy pedal and/or increased pedal travel in an otherwise sound system, you are wrong. There is no cause:effect relationship there. 100% of the time. No exception. If you could offer an explanation to support your position, I'm sure you would have done so by now.

Next, I'm not confusing air in the MC reservoir with air in the system. I offered this link to help you understand how your assertion that "Unless someone opened up the system air getting in is rare" is also wrong. Obviously, you didn't take the time to enhance your understanding. I can't do anything more to help you.

As far as having my head in my can . . . well, I'm not surprised that you resorted to personal insults when you found your position to be indefensible.

You mention you work on cars 'all the time'. I assume you earn your living repairing autos. Wait. Maybe that's the answer. Why would you solve a problem by simply bleeding the brake system, when you can convince the customer that seizing is the culprit, and sell them a complete rear brake r&r and then bleed the system in the process. This way, the problem gets fixed, you get a nice commission on the job, and the customer is none the wiser.

Sounds like you may work for a dealership. Do you?

[05DCLB]

Duh, I was just drivin' down the road and all this air got in my brake system. I hate when that happens.