New power break booster and cylinder are not working. . .need help

[juno]

My break power booster was making strange nose, so I purchased a new one the other day. Today I took the booster off and discovered break fluid inside of it. So I rushed to the parts store and got a new master cylinder. I installed both: master cylinder and the vacuum booster. Now my brake light would not go off and the brake pedal has no pressure when the engine is on.

I tried pumping the break pedal for about an hour per the instructions that came with the parts, but the breaks still have no pressure.

Any advice would be greatly appreciated.

Thank you in advance.

-J

[dksob81]

you prolly have air in the system and it will need to be bled completely, you will also need to activate the ABS pump to be sure to get all the air removed from the abs pump.
bleed brakes with pressure (pumping brake pedal) first. Best way is to pump pedal once and hold to the floor while having someone crack the bleeder open, start farthest from the Master Cylinder (which would be the right rear, then LR, RF, LF. Do each wheel until you get all air out. Gravity bleeding might be a good idea to do first.

to gravity bleed - crack all the bleeders and remove cap from Master Cylinder. Be sure to keep an eye on the fluid level in the Cylinder do not let it run dry.

Then pressure bleed - like I mentioned above.

then using a DRB III scanner (or equivilent) bleed the system using the ABS pump. - this might not be totally necessary - but is part of the proper bleeding procedure according to my FSM for my 94.

then pressure bleed again.

[jaz1314]

Certainly bleeding is a necessity and you should do that FIRST and do it correctly.

In addition to that, some of the aftermarket boosters have adjustable apply pins inside to adjust the travel of the plunger that pushes applies your master cylinder. if the pin is too short it will casue the pedal to travel too far. Likewise, if it is too long it can cause brake drag because it wont return far enough to clear the line passages. I just replaced the booster and master cylinder ( first the master went then the booster started making a WHOOSH sound under the dash about a week later ) in my 94 JGC. In the box with the booster was a sheet with instructions on adjusting the push rod. Ill type out for you what mine said in case yours was missing, but try the bleeding first.

" Remove the reservoir cap. While an assistant presses the brake pedal look for fluid to erupt in th reservoir when the pedal is depressed 3/8 to 1/2 inch. This indicates correct push rod length. On dual master cylinders, fluid may onnly erupt from the front reservoir.

If the pedal travels more than 1/2 inch before fluid erupts, the push rod is too short. If nothing happens no matter how far the pedal is pushed, the rod is probably too long".

to adjust remove the master, using a pair of pliers turn the rod adjustment nut in to shorten and out to lengthen.;

Good luck

Originally Posted by juno

My break power booster was making strange nose, so I purchased a new one the other day. Today I took the booster off and discovered break fluid inside of it. So I rushed to the parts store and got a new master cylinder. I installed both: master cylinder and the vacuum booster. Now my brake light would not go off and the brake pedal has no pressure when the engine is on.

I tried pumping the break pedal for about an hour per the instructions that came with the parts, but the breaks still have no pressure.

Any advice would be greatly appreciated.

Thank you in advance.

-J