2003 Celica - Soft brake pedal
Discussion
I've got a brake problem. The car's not moved much for the past 5 months, the brakes were perfect when parked up.
The problem is a soft pedal when the engine is running, the pedal is hard when the engine is off. All the calipers are sliding, the pistons are free and all the Flexi hoses were new a year ago. There's no air in the syste.
Could it be a servo or master cylinder problem? Anyone had the same issue?
The pedal does pump up when driving to give good braking.
The problem is a soft pedal when the engine is running, the pedal is hard when the engine is off. All the calipers are sliding, the pistons are free and all the Flexi hoses were new a year ago. There's no air in the syste.
Could it be a servo or master cylinder problem? Anyone had the same issue?
The pedal does pump up when driving to give good braking.
You seem to have checked all the likely sources. I guess you've still got one of the problems you mentioned.
If one half of a tandem master cylinder fails then you will get a soft pedal, but also only get braking on half the wheels. You say they're all working, which seems to rule that out. The only other way I can see for a soft pedal is flexibility in the system - either in the fluid, or mechanical flexibility (expanding hoses, stuck pistons causing the caliper to flex under unequal side loads, that sort of thing).
Old fluid doesn't feel as good as fresh fluid, so if you have run out of ideas a flush would do no harm and might help.
If one half of a tandem master cylinder fails then you will get a soft pedal, but also only get braking on half the wheels. You say they're all working, which seems to rule that out. The only other way I can see for a soft pedal is flexibility in the system - either in the fluid, or mechanical flexibility (expanding hoses, stuck pistons causing the caliper to flex under unequal side loads, that sort of thing).
Old fluid doesn't feel as good as fresh fluid, so if you have run out of ideas a flush would do no harm and might help.
I've fixed it.
I went over the front calipers again tonight and found a couple of small problems. The pads weren't sliding as freely in the calipers as they should be, I filed them slightly. The other thing was the rubber boots covering the sliding pins had a build up of rust pushing the rubber into the pin stopping it sliding as well as it should. It was hardly anything but it was enough.
I've been working on cars a long time but I've never experienced anything like that before. It felt like the master cylinder had gone.
I went over the front calipers again tonight and found a couple of small problems. The pads weren't sliding as freely in the calipers as they should be, I filed them slightly. The other thing was the rubber boots covering the sliding pins had a build up of rust pushing the rubber into the pin stopping it sliding as well as it should. It was hardly anything but it was enough.
I've been working on cars a long time but I've never experienced anything like that before. It felt like the master cylinder had gone.
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