ok....my peddle went clear to the floor [no brakes] this morning and i had to pump them roughly 5-6 times before the normal feel, and now are just spongy.....i'v gone over this thing for a year now...when its cool i have to pump them a few times then its fine the rest of the day.....all new brakes, lines, bleed them 5x, NO leaks, res is still full....what the hell is up with this? do any of you guys have any ideas?

 

Sounds like a bad master cylinder to me. Have you replaced/rebuilt it? When you come to a stoplight does the brake pedal slowly go to the floor with steady pressure while waiting for the light to turn green?

 

it will work fine one min then another min later it will go clear to the floor with easy....no slow ped drop

 

Still sounds like the master cylinder is going bad. I'm sure someone else will chime in if I am incorrect. I personally would replace it though, everything else is new. My pedal is starting to get soft, so once it warms up and melts all this damn snow I am going to replace mine.

 

Master cylinder or a leak in your booster. Also, do you have drums or disks? If you have drums, you may need to replace wheel cylinders. I've had them leak before.

 

yeah it needs a master. now. kind of a safety issue

 

thanks guys....i'll try it.....oh and it s gsl-se

 

If you aren't losing fluid, then the MC is the only other possibility. Once the internal seals begin to wear, fluid can slip past them resulting in your pedal descending to the floor.

If you press on the pedal very hard, it will actually stay "pumped up" longer and descend more slowly. This is because that extra force is distorting the seals and causing them to seal more effectively. This is a good way to test the condition of your MC, just hold th pedal lightly (like you were just sitting at a stop light) and see if the pedal starts going down. If it does, then the seals are worn.

But, back to your issue. Even though this only happens intermittently, I would still replace the MC. It could be that once those seals are warm, they seal better due to improved conformity. Cold seals would be less likely to fill gaps, etc. and make a good seal.



One other tip while we're on this subject. When bleeding the brakes, don't allow the brake pedal to descend any farther than it would under normal circumstances (I usually place a small block of 2x4 under the pedal). Why? Because if the cylinder travels farther down that bore than it normally would, it travels over surfaces that have not been smoothed down for that use. So, the seal travels outside it's normal range, catches a burr or rough spot in the bore, and now you have a damaged seal. How many times have we read "it's not my master cylinder, because I just replaced it"?









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