Brake pedal soft when slow, hard when fast. Master Cylinder Failure?
#1
Brake pedal soft when slow, hard when fast. Master Cylinder Failure?
1994 Lexus GS300
A few days ago the brake pedal got started going all the way to the floor. Came on suddenly and no work has been done lately. First I checked the fluid level, just a bit low, not down to minimum but I brought it up to max. Didn't help, and level has not dropped since. So started researching and found the suggestion to compare a slow pedal push and a fast pedal push. If pressing slow goes to the floor, but pressing fast doesn't, that apparently points to a master cylinder failure. Sure enough, that's what it does, slow goes to the floor, fast gives a hard response. So it appears to me I have a failed master cylinder.
It looks like it's a simple matter to change the master cylinder. I see three bolts, a couple metal lines, a hose or two...voilą!
1) Does anyone think any different? Could the brake booster be a problem?
2) Is there a way to test the master cylinder before replacing?
3) If I change the master cylinder, what do you recommend I use?
4) Does anyone have advice, tips, or tricks?
master cylinder
under master cylinder
master cylinder starboard
A few days ago the brake pedal got started going all the way to the floor. Came on suddenly and no work has been done lately. First I checked the fluid level, just a bit low, not down to minimum but I brought it up to max. Didn't help, and level has not dropped since. So started researching and found the suggestion to compare a slow pedal push and a fast pedal push. If pressing slow goes to the floor, but pressing fast doesn't, that apparently points to a master cylinder failure. Sure enough, that's what it does, slow goes to the floor, fast gives a hard response. So it appears to me I have a failed master cylinder.
It looks like it's a simple matter to change the master cylinder. I see three bolts, a couple metal lines, a hose or two...voilą!
1) Does anyone think any different? Could the brake booster be a problem?
2) Is there a way to test the master cylinder before replacing?
3) If I change the master cylinder, what do you recommend I use?
4) Does anyone have advice, tips, or tricks?
master cylinder
under master cylinder
master cylinder starboard
Last edited by bloodyKnuc; 11-15-15 at 09:55 AM. Reason: added photos
#2
As a simple and cheap way to investigate the brake failure a bit further, I did a quick change of the brake fluid. I used a turkey baster and sucked the fluid out of the reservoir then refilled.
This helped a little but still not working properly.
The next thing I plan on doing is a complete fluid change, not expensive but a little more involved flushing the fluid through the system.
Looks like master cylinders are about 120 bucks. They look easy to change but I want to be as sure as I can before incurring that expense.
This helped a little but still not working properly.
The next thing I plan on doing is a complete fluid change, not expensive but a little more involved flushing the fluid through the system.
Looks like master cylinders are about 120 bucks. They look easy to change but I want to be as sure as I can before incurring that expense.
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