Brakes not working

Tiny
MGZSAK
  • MEMBER
  • 1994 GEO PRIZM
  • 1.6L
  • 4 CYL
  • 2WD
  • MANUAL
  • 120,000 MILES
After a hard, emergency stop to avoid a deer in the road my brakes stopped working properly. The brake pedal now basically goes to the floor and what little braking there is causes the car to pull to the left.

I've tried a number of things without any success getting the brake system back to normal. Here is what I have done:
- Replaced the master cylinder.
- Replaced both hard brake lines going to the rear of the car (they had a number of rust areas).
- Bleed all four wheels.
- Disconnected the vacuum line going to the brake booster and confirmed (with a vacuum pump) that it doesn't have a vacuum leak.

I should also mention that when the engine is not running the brake pedal has some, but not much resistance. With the engine running there is basically minimal pedal resistance.
Thursday, June 11th, 2020 AT 3:01 PM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,126 POSTS
Hi,

If there are no leaks, either you got a bad master cylinder or there is still air in the system. Here is the sequence (order) for bleeding the brakes on this vehicle:

Front wheel drive models: RR-LF-LR-RF

Did you follow that order? Can you explain how it was done to me? Also, have a helper press the brake pedal while you watch the rubber brake hoses at the calipers. Make sure they aren't expanding.

Let me know.
Joe
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Thursday, June 11th, 2020 AT 9:31 PM
Tiny
MGZSAK
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Joe,

Thanks for the quick reply.

Didn't do the brake bleeding in the order you listed. I've always done brake bleeding starting with the wheel furthest from the master cylinder and working to the nearest (in this case RR, LR, RF, LF). Was done the old fashion way with a helper (my wife) in the car pressing on the brake pedal while I opened/closed the bleeder valve.

I did a visual of the brake hoses. They looked okay but didn't check if they expanded when the pedal was pressed.

I did check the RF caliper for movement. Had my wife step on the brake while I had the caliper off and a big C clamp and steel block held against the piston. I was surprised to find when I back off the C clamp a little and she pressed on the brake the piston would move only an 1/8 of an inch or so. Was expecting the piston to shoot out and hit and steel block hard, like when it is being removed with compressed air for a caliper rebuild.

When I bench bled the master cylinder it got harder to push in the piston but never to the point I couldn't push the piston in. Should it have gotten to the point I couldn't move the master cylinder piston? If that is the case I'll have to pull it and try the bench bleeding again to verify if it is defective or not.
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Friday, June 12th, 2020 AT 4:48 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,126 POSTS
Hi,

The sequence you used when bleeding is the common way it's done. I would try doing it the way the manual indicates. Also, let me know if the vehicle has ABS.

As far as the master cylinder getting harder when bench bleeding, that shouldn't happen. All you are doing is pressing unrestricted fluid back into the reservoir until the air is gone. I wonder if you just simply got a bad master cylinder.

Try the bleeding as indicated. If that doesn't make a difference, replace the master cylinder. It's been awhile. I don't remember the push rod as being adjustable.

Let me know if I can help in any way.

Joe
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Friday, June 12th, 2020 AT 9:58 AM
Tiny
MGZSAK
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  • 5 POSTS
Joe,

Thanks for the suggestion. I'm tied up the next few days so don't expect to be able to work on the car until sometime next week. Will let know how I make out.

Mike
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Friday, June 12th, 2020 AT 12:59 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,126 POSTS
Sounds good, Mike. Make sure when you bleed them that the pressure is substantial when you open the bleeders.

Take care,
Joe
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Friday, June 12th, 2020 AT 11:05 PM
Tiny
MGZSAK
  • MEMBER
  • 5 POSTS
Joe,

Finally got some free time to get back to the brakes. Checked the master cylinder and it is fine, not the cause of the problem. Bled the brakes following your suggested sequence. Noticed the right front did not have as great a flow or pressure of brake fluid as the left front, for example. Given both are on the same brake line circuit I suspect there may be a partial blockage in the right front brake hose so I took the hose and caliper off the car. While I didn't see any cracks it is hard to tell if the hose has a partial blockage under high pressure so decided to replace the hose. While the caliper is off I thought I would check the piston and bore for any rust or damage. Bottom line is a new hose and caliper rebuild kit are on order. Should get the parts from Rock Auto in a week or so.

Will keep you updated on how things work out after the new parts are installed.

Mike
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Monday, June 15th, 2020 AT 2:35 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,126 POSTS
Mike,

I have seen the rubber hoses deteriorate internally and cause a caliper not to release. Let me know how things turn out for you. I'm interested in knowing.

Joe
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Monday, June 15th, 2020 AT 7:18 PM
Tiny
MGZSAK
  • MEMBER
  • 5 POSTS
Joe,

I rebuilt the front right caliper and replaced the brake hose. Went ahead and bled all four wheels once more. Brakes are now working fine.

Thanks much for all your help.

Mike
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Wednesday, June 24th, 2020 AT 12:16 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,126 POSTS
Hi Mike,

I'm glad to hear it's fixed, and you are very welcome. I hope if you need help in the future, you come back. You are always welcome to return.

Take care,
Joe
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Wednesday, June 24th, 2020 AT 9:23 PM

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