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I have a good understanding of brakes, but I am seeking some direction. I have a 96 Grand Cherokee that has an issue with the brakes. The pedal has excess travel, and the stopping distance increased. If I pump the pedal once or twice, it improves. I did a visual inspection of all of the brake lines, hoses, pads, rotors, calipers, etc. The pads still have some life left in them, I did not see any leaks, and it does not appear to be losing brake fluid from the reservoir. The pedal does not seem spongey, like there is air in the lines, it just has excess travel. If I pump the pedal with the engine off, it gets firm after 2-3 pumps like normal, and stays firm. The symptoms make me think that the master cylinder is at fault, but I am aware that they can fail, and not show any external leaks. I am wondering what I should check first. Thank you in advance.
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Totally different car, but I just had this same complaint/symptoms on a old Mitsu Eclipse last week. It turned out to be a seized brake caliper. They only got a few minutes of diag time from the customer so I wasn’t willing to take the wheels off and fully/properly disassemble and examine all the calipers and slides. Everything looked good underneath and the pads and rotors were old but still looked fine. I decided to go around cracking bleeder screws one at a time to see if any air happened to come out. First 3, clean fluid and maybe just a small bubble that doesn’t matter. Last one, nothing comes out and I waited and waited, still nothing. I pushed on the caliper (very hard) from behind to compress the piston a little, and some ‘rust fluid’ came out of the bleeder. Loosened the fluid line going into the caliper and confirmed clean brake fluid came right out, and there you have it. The brake pedal felt just like you’re describing.
That kind of makes sense. The problem came to be as I was pulling off the lot of an automatic car wash when it was 10-15 degrees Fahrenheit. So, I was looking for a reason it would have happened then. The soap/water/ice could have just finished off a caliper on its last leg.
[quote=”mikeywil0003″ post=127655]That kind of makes sense. The problem came to be as I was pulling off the lot of an automatic car wash when it was 10-15 degrees Fahrenheit. So, I was looking for a reason it would have happened then. The soap/water/ice could have just finished off a caliper on its last leg.[/quote]
Really? Do you believe that? Those are sort of made for water and ice and cold.
What you describe is a worn out or air saturated brake fluid. When was the last time it was changed, on a 96 car? As inevitably hydraulic qualities of it go worse over the time.Next thing to consider is internal blow by leak inside brake master. Fluid gets past rather old seals.
I’d start with checking on fluid quality in reservoir, and bleeding brakes. Should you have had fluid fresh/-ly changed, I’d go for MC rebuild.
Should you have seizing caliper – you’d have known this. It kinda shows. Now, also, seizing caliper overheats brake fluid, and as the result, it boils and saturates with air bubbles – yes, loosing it’s resistance to compression.
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