My wife's car (98-SW2) started experiencing excessive brake pedal travel recently. The pedal goes almost to the floor but there is enough braking action to stop the vehicle.

So i researched the forums and concluded that the master cylinder was failing. Purchased a rebuilt unit, bench-bled, and reinstalled in the vehicle.

Excessive brake pedal travel is still there and no visible leaks.

So, I researched further and saw some posts that implied front/rear brake wheel assemblies could cause excessive brake pedal travel ? The only thing I did recently was remove the right rear drum to check the status of the brake shoes - they appeared to be acceptable.

Question 1: Can anyone confirm and explain how front/rear brake wheel assembly failures (other than leaking) could cause excessive brake pedal travel?

Question 2: I will bleed the lines tomorrow with another helper but expect the problem to still be there. What other items might be causing the problem?

 

Check your rear wheel cylinders very closely. I had that happen on a Grand Caravan that I own and there were no visible leaks. Upon removing the rear drums, I found that both wheel cylinders had small leaks. If you see a kind of wet, dark build up of dust around the wheel cylinder, replace BOTH along with the hardware. I never replace one caliper or wheel cylinder, always both if one is bad. That way, I know there isn't a weak place in the system to fail again anytime soon. Also, if you find that you don't have a leaking wheel cylinder, check your brake hoses for soft spots. They break down internally and may be collapsing and not allowing proper flow of the brake fluid. If all seems well, bleed them ALL in the correct order. Right rear, left rear, right front, left front. This gets the air out of the longest lines to the shortest line, one at a time. Lastly, if you got that M/C from Autozone, it wouldn't be anything unusual for it to be defective. I worked for them for 5 years and saw a lot of stuff come back defective, right out of the box.

 

Search the internet on when to replace front brake pads and rear shoes.

While your at it, search the internet on how to properly adjust drum brakes.

No I'm not going to take the time to explain what you can look up for yourself.

 

Rubehayseed, I did buy the M/C from Autozone. I would have bought a new one but none were in stock. Also, I noticed that the rebuilt M/C multiple punch marks around the flange that bolts to the booster - wondering if those marks represent how many times the M/C was rebuilt?

I will pull the rear drums (when the rain stops) and check the wheel cylinders. If no leaks are found I will bleed the brakes in the order you recommended (RR, LR, RF, LF). I'm reluctant to swap out the rubber lines for now only because I already made one change - if I make too many changes, I fear I may loose track of the original problem.

More Symptom Info:

Since my last post I took the vehicle out on a test run and was able to lock up at least one or both front wheels on a wet road surface (not sure what wheels are on what brake circuit circuit).

Also, I applied significant pressure to the brake pedal before starting the vehicle. When I started the engine the pedal sank to the floor, which I can't seem to explain. I realize that the booster assists by reducing the breaking force required at the pedal, but I did not expect the pedal to travel as much as it did considering how much force I applied initially. Maybe its my lack of experience working with break boosters?

Will update after I check the rear cylinders and bleed the brakes.

 

It's normal for your brake pedal to drop some with your foot on it when you start the car with power brakes. It's not normal for the pedal to go to the floor. It sounds like the power brake booster and master cylinder are working properly, so I'm guessing that you need to bleed the brakes again. Make sure you keep the master cylinder full and don't let it go dry. As a rule of thumb, I have someone pump the pedal and hold it for me 4 times in a row while bleeding each wheel cylinder. I make sure to check the master cylinder after doing each wheel 4 times. I've never had a master go dry this way and have always succeeded in removing all the air from the lines. As far as the brake hoses go, you don't need to replace them. Just pinch them with your fingers from one end to the other. They break down from the inside out. If you hit a soft spot where you can pinch the hose together, then that hose will need replacing. If no soft spots are found, then you should be okay with them. Also as sw2cam suggested, your rear shoes may just need adjusting. If you can slide the drums off without any problem then you need to adjust them out until they drag and are hard to pull off.

 

Uh-huh, and be sure to bleem 'em in proper order. Start with the wheel farthest away from the master cylinder (RR), then continue on to the rest (LR), (RF), (LF)

 

Update:

OK so I inspected the RR wheel clinder an noticed it had a greasy surface so I went out bought 2 new wheel cylinders and installed them and started the bleeding process (RR, LR, RF, LF).

Bleeding the rear wheel cylinders went as expected.

When I tried to bleed the RF caliper, very little fluid came out. I repeated the process multiple times (over 10) of having me helper press the brake pedal, open the bleeder valve slightly, closed the bleeder valve before the pedal reached the floor, slowly raise the pedal, and start the process over.

The LF caliper bleeding responded as expected.

After completing the bleeding process the excessive pedal travel problem remains.

I did not think to check the hose on the right front caliper but I will do that tomorrow.

Also, I noticed that one of the pads on the right caliper was worn so I plan on replacing the front pads and rotors (and maybe the calipers as well).

I will also look for kinks in the front brake lines as this may be preventing fluid in the lines from reaching the caliper.

Any other ideas on what the problem might be are appreciated.

 

If your inboard pad was worn more, then odd are either the caliper or hose is no good on that side. If it's the outboard pad, then you may just need to replace the guide pins and boots. Be sure to lubricate them with some brake lube. Just ask your parts sales person at the parts counter. They SHOULD know what to recommend.

 

Honestly, I feel that my saturn has exessive brake pedal travel, and ive never really liked it. Even when I did the rear disk swap the pedal travel didnt improve. The car always stopped and stopped fine, ever since I did the rear swap the brakes are pretty good - its just that pedal travel that worries me
ex. if im sitting at a light, i can push the pedal to the floor without a whole lot of effort

 

Sounds like you may have a small leak in the power brake booster diaphram to me, Octavious. BUT, keep in mind that I'm not an ASE certified mechanic. Never claimed to be a mechanic and never will. I too much respect for the guys that really are.