When I hit the brake repeatedly at idle the rpms jump up?

[bdog9seclx]

What could this mean? and also the dome light will barely dim...

thks

 

[Michael Yount]

The power brakes are powered by engine vacuum - you likely have some sort of vacuum leak related to the power brake booster operation.

 

[bdog9seclx]

just replaced that hose and zippy tied it to make sure good idea tho

 

[PRO50SC]

It still pulls vacum from the motor espacially if you are doing it repeatedly.

 

[Michael Yount]

....uh, I was thinking the booster itself; if it's damaged internally (the diaphragm) it can leak internally. Replace the hose all you want -- if the leak's internal to the booster, a new hose - even a zippy tied one - won't help any.

 

[Maryland Stang]

The light dimming is because you're hitting the brakes making the brake lights come on. It may be that your alternator is on it's way out. Do you have under drive pullies? How many volts are at the battery when the car is idling?

 

[bdog9seclx]

how many should be? alternator is good have a lot of stuff running off battery

 

[HISSIN50]

how many should be? alternator is good have a lot of stuff running off battery

~12.6 volts and above is where you want to be. Less than that and you are discharging the system. However, it can be normal to see a state of discharge at hot (stock) idle with some (or one ) accessory turned on. U/D's can make it worse.

Good luck.

 

[5spd GT]

The light dimming is because you're hitting the brakes making the brake lights come on. It may be that your alternator is on it's way out. Do you have under drive pullies? How many volts are at the battery when the car is idling?

That was my thinking as well...