Poor Break performance
Thread Starter
Melting Slicks
Joined: Feb 2008
Posts: 3,412
Likes: 118
Poor Break performance
I took my 75 out for a ride the other day and noticed it didn't want to stop very well. It was fine two days before. I even braked hard on gravel and it would not even slide. Will moisture in the fluid cause that? I checked and it looks to me as though it has moisture in it because you can see a separation of fluids as you would when you mix oil and water. I also thought maybe the proportioning valve could be stuck. Other than that I know the previous owner changed all the fluids and it appears as though the master cylinder is new. There are no leaks in the brake system. Also both front brake lines are new. What do you think?
Last edited by Monterey C6; Sep 26, 2019 at 11:59 PM.
Safety Car
Joined: Sep 2007
Posts: 4,454
Likes: 328
From: Indy Indiana
does the pedal drop further than it used to? if so, then bleed.. ( find the leak first.. how did air get in there?)
else there might be fluid or contamination on the rotors.
get you one of thoses cheap infrared temperature guns.. take your car for a drive, exercise your brakes, then take temp on all 4 rotors. the coldest will not be grabbing correctly.
else there might be fluid or contamination on the rotors.
get you one of thoses cheap infrared temperature guns.. take your car for a drive, exercise your brakes, then take temp on all 4 rotors. the coldest will not be grabbing correctly.
Le Mans Master
Joined: Aug 2006
Posts: 7,417
Likes: 1,554
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
#1 Bleed the brakes.
#2 Confirm that the bearings are good and adjusted to specifications.
#3 Check the rotor run out.
#2 Confirm that the bearings are good and adjusted to specifications.
#3 Check the rotor run out.
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
Was and is the master cyl full? If yes bleeding is always a good idea. Do you have good pedal height? Next would be to inspect the disc pads, organic pads can become glazed and harden. Replace pads and I always liked taking a orbitol sander [DA] to the rotor surfaces. T
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
When you say new front brake-lines, do you mean the steel ones or the rubber ones?
Only the front rubber hoses gets a "one-time-use" copper washer between the hose fitting and the caliper. If that is not installed, you could be losing pedal pressure at the front due to a poor seal. It may or may not even leak there.
If it were mine, I would purchase the correct copper washers, then remove the front hoses for inspection. Install new washer, then a complete flush is in order with a couple big bottles of DOT3 back to front.
Only the front rubber hoses gets a "one-time-use" copper washer between the hose fitting and the caliper. If that is not installed, you could be losing pedal pressure at the front due to a poor seal. It may or may not even leak there.
If it were mine, I would purchase the correct copper washers, then remove the front hoses for inspection. Install new washer, then a complete flush is in order with a couple big bottles of DOT3 back to front.
