This is in regard to a 2002 Daewoo Lanos, but I don’t think there’s anything special about this model when it comes to the brakes and wheel hubs, etc. This is the base model, which does NOT have ABS.
Before touching the brakes on this car, the pedal was firm and it had good stopping power. I used a piston retractor to push the pistons in, without opening the bleeder screw, and replaced the pads and rotors with decent quality parts. Now, the brake pedal doesn’t get firm until about 1/2" from the floor, and the stopping power is poor.
I don’t see any external brake fluid leakage, and the reservoir is full to the top (the level got higher from putting new pads). The pads which were replaced were nearly used up, as the friction material was about as thick as a U.S. dollar coin.
I am looking for advice on what might need to be replaced in order to restore the proper braking performance.
Do I need to replace the calipers and hoses, or does it sound like the master cylinder has gone bad? Any advice, besides “tow it to a shop” would be appreciated. I’d rather fix it myself, if possible, before shelling out possibly thousands of dollars.
I’m going to say I don’t know but it acts like there is air in the system or they need to be bled. By not opening the bleeder, you pushed the old fluid back up the line. Maybe affected the master who knows? It’s a guessing game now but I’d start with a fluid exchange and having them bled.
Edit: seeing testers comment, guess you need to decide on replacing the master first and then the fluidvexchange. Some are cheap.
I would try to bleed the brakes, cheap to do, but it sounds like you may have damaged an internal seal in the master cylinder as already mentioned above…
To confirm, clamp off all the brake hoses and see if the pedal still feels the same or not, if the pedal still feels the same, replace the master cylinder, if it is very hard, then you have to unclamp one hose at a time to see what hose/caliper/wheel cylinder is bad, when you (takes 2 people) unclamp one hose the pedal will drop about a 1/2", if it does, re-clamp hose and move to the next hose, should get the same 1/2" drop (about)… If you unclamp one hose and the pedal drops way down or close to the floor, then it is in that caliper/wheel cylinder area…
If the pedal drops close to the floor, check the wheel bearing for that wheel to see if it is loose, a loose wheel bearing can make the pedal drop also…
I’m guessing that when you pushed the brake pedal down several times to extend the caliper pistons after installing the new pads, you pushed the master cylinder beyond what it has been normally traveling, possibly pushing the piston and seals into some of the muck that has accumulated there over the past 20 years. Probably time for a new master.
Good point. I’ve developed a habit of doing lots of short strokes with the pedal until I feel resistance versus a few long ones to avoid this kind of issue. Takes a little longer but haven’t had any issues doing it that way.
If I had this problem my first guess would be a faulty master cylinder, but before replacing it I’d bleed the brakes (slowly, using the gravity method if possible) and double check that nothing looks suspicious involving the booster. The symptoms alone, without knowing about the pad replacement job, that would make me think something about the booster system has failed. Does the engine still idle as good as it did before, and is there any increase in the amount of smoke out the tailpipe?
All good advice and this may have nothing to do with the OP’s issue but a week ago I experienced “spongy” brakes on my 2004 Hyundai after doing a pad change on similarly worn pads.
Had noticed that even after cleaning the calipers the new pads were still pretty tight and in an after check noticed that the brake fluid was above the maximum fill line so removed some fluid and after some “back and forth” in the driveway, the brakes returned to normal.
No idea of the root cause; overfill of the fluid, crud that got pushed in when retracting, corrosion in the cylinders, worn/stiff seals, at 20+ years old it could be all of the above.
I am going to order a new master cylinder. Anything else I should replace, such as the rubber hoses going to each caliper/drum? Any special tricks to clearing the air from the system afterward? Open all the bleeder screws at the same time, or one at a time?
Some cars, especially older ones, gravity bleed well. One or all lines open if you have 4 bleed bottles. Be patient, it takes a while.
Be sure and do a bench bleed on the master before it goes in. Also have an assistant push the brake pedal and crack each master cylinder line open so that the last bit of air gets out and dribbles a bit of fluid.
If you can keep the helper around for a short while, you can bleed each corner one by one quite quickly.
As was mentioned by @Tester, I had never heard of the “one man Bleeder Hose.” I use a “Brake Bleeder and Vacuum Pump Kit” sold by Harbor Freight for bleeding a system after a brake job or when performing a brake fluid flush…
Those kits are handy for many things. I’ve had a “MityVac” for many years. More expensive, but it’s held up well. The HF/Pittsburgh once might too tho’
Right now I’m using it in lieu of an actual vacuum pump to check/fix leaks in a manifold gauge set.
Maybe this is something simple. Here’s a couple of other ideas: 1. You must completely clean the anti-rust coating from new rotors before you install them. 2. It can take some amount of stopping time before newly installed pads bed correctly to new rotors. Google “how to bed pads and rotors”.
How many of you old timers remember the Brake Shoe Lathes? Actually if you ever used one of these, it’s a wonder we are still alive and not long since dead from the brake dust they created that was asbestos laden…
For our younger set, these were used to grind off the high spots of new brake shoes to allow the shoe to seat quicker… You mounted the brake shoe in the swing and adjusted to the brake drum diameter and you would swing the shoe back and forth in an arc to grind off all the high spots. The center vertical cylinder contained a grinding wheel the removed the shoe material. And if that was not bad enough, most of us smoked while we did it…
Never did that, but I did blow the dust off the drum brakes before replacing the shoes for dozens of brake jobs, quite a cloud of asbestos dust. I must not have been susceptible, luckily.
Same, but I used my homemade about 24" long straight through no trigger (NOT OSHA approved lol) brake line to nipple wand to blow a cloud of dust, then blow it away from me as I attempted to hold my breath… Sadly it was way more than a few dozen… lol
The gas station I worked at did not have one. We took drums to a shop about a mile away. Guy that turned the drums was a year ahead of me in high school.
