ultraclyde Reader
Jan. 15, 2011 6:33 p.m.

Okay, gang, I'm workign on my mom's Corolla and I need a consult. It's a '96 model with eleventybillion miles and the brakes are acting up. The story so far:

It started having episodes where it would act like the parking brake was on. You pull up to a light and stop normally but when you start to pull off it would almost kill the engine, lug down and not roll. After several applications of the brake or parking it for a little while, it would miraculously cure itself. Until it didn't. I never experienced this first hand and when it locked up the last time she took it to a garage since I was busy. For once. They replaced both rear flex lines (collapsed) and replaced the proportioning valve.

After that the brake pedal went too far to the floor and felt mushy but did stop the car and would lock the brakes. My impression was the brakes needed rebleeding but I didn't have time to do it. She decided to drive it that way since it would stop and she was without funds to take it back.

Now things are getting worse. Sometimes you can pull up to a light and stop normally, then when you pull away you get a hard..rumble or pulsing sound and the brakes are obviously dragging. Top speed is about 35mph with it floored. If you step on the brakes to a full stop, it will clear up at some point and the brakes feel as they did before - mushy but workable.

Tonight she calls me and has a new issue. Driving to the store and suddenly the pedal is rock hard and only goes down an inch. It also doesn't want to stop the car.

Wiskey Tango Foxtrot??!! I'm thinking master cylinder or maybe brake booster? It IS an ABS equipped car, what are the symptoms of a bad ABS...actuator thingy?

Anybody have any ideas? Help me out guys, she's bringing out tomorrow for me to look at.

AngryCorvair SuperDork
Jan. 15, 2011 7:09 p.m.

IDK what it is, but i suspect a caliper that isn't sliding properly. here are some things you can do to help diagnose:

  1. does it release if you put the car in reverse and back up a foot or so?
  2. if it happens to you, get out and check which wheel center feels hotter than the others. that's the one that's dragging.

oh, you can tell when the abs actuator thingy is bad because it quits actuating.

Strizzo SuperDork
Jan. 15, 2011 7:22 p.m.

Didn't grm have a similar issue on track with their spec e30? Iirc they tracked it down to a bad abs actuator/module

44Dwarf Dork
Jan. 16, 2011 6:30 a.m.

I wonder if the shop got all the air out of the ABS module. The air could be getting warm and expanding thus locking a caliper. Some times you need to send power to the abs thingy while bleeding to get all the air out or so I'm told. My 96 f150 had rear abs and took me forever to bleed. later i found out about the ABS actuation. I've read some mfg have a way to do it thought the OBDII connection.

Other thoughts are bad master might have a rip in a lip seal that sometimes lays over allowing fluid past thus low pedal then next time roll over and block the return port so brake drags and heat generated adds extra force and self feeds.

44

ultraclyde Reader
Jan. 16, 2011 9:23 a.m.

Thanks for the input guys. I'm not sure if it's an ABS or nonABS model. Guess I'll find out today.

My first reaction was caliper, but it doesn't pull left or right at all. Whether malfunctioning or not, it always stops straight or pretty dang close. I can't imagine both calipers malfunctioning and then releasing simultaneously.

93gsxturbo
93gsxturbo HalfDork
Jan. 16, 2011 3:47 p.m.

I have seen similar symptoms from failed rubber lines. Replace all the rubber flex lines, clean and inspect all the caliper sliders for uneven pad wear.

You can diagnose which corner is giving you issues if you crack a bleeder once the brakes lock up and don't release. One bleeder will have pressure behind it and squirt out, the other 3 will just dribble out.

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