The booster won't cause a low pedal. What led you to the master cylinder? Did you bench-bleed the new one? Have checked for misadjusted rear shoes? How about leaking wheel cylinders?

Answered by caradiodoc (expert)
17,308 answers provided

some pedal push rods are adjustable for length. the question is, when and why did this problem start?

Answered by fixitmr
24 questions asked

brakes have been mushy for quite a while....replaced lifetime warranty brake pads several times.there was a factory recall on master cylinders that bleed internally for 06...called factory gave vin # they said my car was not covered by recall. replaced master cylinder, bled brakes put new pads again....still mushy....brakes also make a whistling sound like it is sucking in air.installed new booster....no luck...noticed idle goes down when applying brakes...checked for vacuum leaks....found none...what is a bench bleed?

Response from grees20
2 questions asked

also adjusted pedal rod from booster....nothing has worked

Response from grees20
2 questions asked

Bench-bleeding is when you mount the new master cylinder in a vise, fill it with new fluid, then pump it manually to expel the air. It's a standard part of replacing any master cylinder. If you don't do that, on some systems you'll never get all the air out when the master cylinder sits in a tilted position. On those where all the air will bleed out, it is going to have to work its way down to all of the wheels to be bled out. There are tricks mechanics use that eliminate the need for bleeding at any of the wheels when they replace the master cylinder, but they still have to bench-bleed it.

A low pedal can also be caused by rear shoes out-of-adjustment. The clue is the pedal will become firm and higher after stroking the pedal rapidly a few times, then holding it. Once it is released, it will be low and mushy again the next time it's pressed.

Answered by caradiodoc (expert)
17,308 answers provided

acts like vacuum leak...as idle sputters when stepping on brake. checked all hoses....cant find a vacuum leak......all other components are new

Response from grees20
2 questions asked

You might be hearing the air entering the back of the vacuum booster. That is what allows the vacuum to pull on the internal diaphragm. If there was a vacuum leak, engine speed would go up quite a bit, not down as you described.

Answered by caradiodoc (expert)
17,308 answers provided

I have the same exact problem with my 06 eclipse with 89000 miles on it. started after 2 "panic" stops. Did you ever find the solution to the problem? thanks for your help.

Answered by dadmarino
0 questions asked

I have the exact problem with my 06 eclipse, same milage too (go figure). Cars in the shop and master cylinder been replaced twice, booster replaced, brakes, everything. Did you ever get it figured out????? Please help

Answered by dadmarino
0 questions asked