rpms raising when i push on the brakes

[DannyJoe]

in neutral, when i press the brakes i get a raise in about 400 rpm. any ideas?

 

[sublyminull]

in neutral, when i press the brakes i get a raise in about 400 rpm. any ideas?

400 additional RPM's?

thats a bit weird never heard of this one before.

 

[DannyJoe]

with the e-brake holding me in place i'll idle around 800 and when i press on the brakes its climbs to around 1300.

 

[thecrash91]

just a press or a few pumps?

 

[slavrenz]

bad brake booster?

 

[2009speed3GT]

The increases in RPM is because the break booster / master cylinder is run off of vacuum, and needs the extra RPM to complete the load cycle. Much like if you turn your AC on you will notice the RPM increases also do to the extra load placed on the motor.

 

[DannyJoe]

thats just a press not pumping. thanks for the input 2009speed3gt

 

[HighSpeed]

The increases in RPM is because the break booster / master cylinder is run off of vacuum, and needs the extra RPM to complete the load cycle. Much like if you turn your AC on you will notice the RPM increases also do to the extra load placed on the motor.

yeah but the a/c compressor doesn't run on vacuum and the ecu is preset to do so if the a/c is turned on because the engine is spinning an extra pulley now. sounds like a leaky brake booster to me. Almost like the diaphragm is craking when you push in the brakes. Do a vacuum test on the brake booster and see how well it holds vacuum, more than likely it will drop fast meaning you have a bad brake booster

 

[DannyJoe]

will do

 

[HighSpeed]

also try to brake really hard and see if you hear any whistling, that will also let you know that it is the booster, or the vacuum line that goes to it

 

[DannyJoe]

good tip. i just had surgery so working on my car let alone even driving my bouncing whip isnt happening. let you all know what comes up when i can