Brake booster or master cylinder???

mikeyc0828

New Member
my brake pedal sometimes looses pressure and i have to put it all the way to the floor to stop other times its real firm and when im sitting at a stop light with my foot on the brake the idle will start to drop and the car will die unless i take my foot off the brake. i heard that if the master cylinder is bad it leaks inside the booster and that causes the vacuum line to suck the fluid up and the idle to drop. i just want to know if any one has any ideas before i start buying parts? any help would be greatly appreciated.
 

Prozon

Kris
It sounds like a brake booster problem.

Are you losing any brake fluid? Brake fluid loss is usually a sign of a master cylinder/leaky line.
 

mikeyc0828

New Member
im not losing a lot of fluid but the fluid level dropped about a quarter of an inch after about 2 months.
 
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PioneerLS

New Member
what if you arent leaking brake fluid? got the same problem but mine doesnt die, although im on 3rd gen
 


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Sean

New Member
I just fixed this problem with my car yesterday. I bet my money its your master cylinder. *"i don't have any money tho"*
One thing master cylinders will do if they are bad is, You stop, hold the brake, and the pedal will slowly move toward the floor. This is a sure sign the master cylinder is bad. A leaking master cylinder or one that sticks, is also a sign it is defective. When you replace the master cylinder replace all the brake fluid in the brake system and bleed the brakes. Moisture in the brake fluid will destroy a master cylinder and this may be why it failed.
 
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seahtech

New Member
always always always always always....did I say always? replace the MC before the booster. Our boosters are generally bullet proof. I have only ever seen 2 fail and one was on a 2010 Pilot lol. MCs are cheaper to replace also. After removing the master cylinder there are several seals that will leak fluid into the booster but it is rarely bad as stated.

The sinking pedal is the obvious sign of MC failure. If you booster is failing typically you will hear a quiet swoosh/squeak noise but no noticable brake performance issues.
 

Sean

New Member
make sure you follow the steps included with your new master cylinder. you need to bleed your mc before you put it in your car or else you will have problems.
 

hidenplanvew

New Member
seahtech said:
always always always always always....did I say always? replace the MC before the booster. Our boosters are generally bullet proof. I have only ever seen 2 fail and one was on a 2010 Pilot lol. MCs are cheaper to replace also. After removing the master cylinder there are several seals that will leak fluid into the booster but it is rarely bad as stated.

The sinking pedal is the obvious sign of MC failure. If you booster is failing typically you will hear a quiet swoosh/squeak noise but no noticable brake performance issues.
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No if the diaphram in the in the booster is bad your brakes will be very hard to push in... you will always hear a swoosh when you push in your brakes thats pos air replacing the Vac from the motor giving you a mechanical advantage

If you do replace the MC you need to bench bleed it first to remove the air from the cylinder and then re attach and bleed the brakes... Can you pump them up while comming to a stop? ya it will be annoying, but should make sure you can stop and remember you have a E brake just so you dont slam into another car..

you can rebuild your MC too, its really simple and pretty up front. You just have to make sure the bore is correct..
 
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