Brake Booster Help

[Afboy143]

I had to install a new brake booster because my old one went out. I had to take the master cylinder out to take the old brake booster out. I put the new booster in and reinstalled the cylinder. (The brake booster piston is sticking out just right) I turn the car on and press the brake to the floor. I pump the brakes and it still happens. Do I need to bleed my brakes? Why is it doing this? The fluid level is right....did air get in the lines ?

 

[Turdle]

Back up a bit please
Why was the first one bad? Symptom?

 

[BrooklynBay]

Were you getting a stiff, or soft brake pedal? As stiff pedal could be the booster, or check valve. A soft pedal could be air in the line, or the master cylinder.

 

[Afboy143]

Were you getting a stiff, or soft brake pedal? As stiff pedal could be the booster, or check valve. A soft pedal could be air in the line, or the master cylinder.

I figured the booster was bad because

1) Stiff brake pedal. I had to push it down pretty far before it would engage the brakes (more than half way)
2) When it did engage, it felt hard like I was pushing the brakes ALL THE WAY DOWN

I just got done doing the brakes. I changed the brake booster and bled the brakes....twice. Its a little better but it still takes more than half way pressed to engage the brakes....it just doesnt feel as hard anymore. The cylider is filled to max and i bled the brakes twice and made sure there was no air. Is a bad master cylinder common? What else could it be? Im out $100 on a booster now so Im on a budget

EDIT: I doubt it could be a leaking/bad line because this problem has been going on for about a week now and I been checking fluid levels in the master cylinder and they havent gone down. Ah i have a stress headache

 

[BrooklynBay]

It might be the booster's check valve. Turn the engine off, wait a few minutes, then unplug it from the booster, but leave the vacuum line on it. If you hear a sudden swoosh, then it was holding vacuum in the booster.

 

[Afboy143]

It might be the booster's check valve. Turn the engine off, wait a few minutes, then unplug it from the booster, but leave the vacuum line on it. If you hear a sudden swoosh, then it was holding vacuum in the booster.

I just installed a brand new (well factory reman) booster so I would think the check valve that came with it is fine?

 

[BrooklynBay]

I've never purchased a remanufactured booster. I usually get them from the junk yard, so I didn't know they came with a new check valve. Did you see if the vacuum line going to the check valve has vacuum? There might be a vacuum leak, or crack on it somewhere.

 

[Afboy143]

I've never purchased a remanufactured booster. I usually get them from the junk yard, so I didn't know they came with a new check valve. Did you see if the vacuum line going to the check valve has vacuum? There might be a vacuum leak, or crack on it somewhere.

The line looks pretty new but I guess looks can be deceiving. I would imagine there is vacuum because if not the brakes would be stiffff like they were when the brakes are pumped when the truck is off. How could I test vacuum? What are the symtoms of a faulty master cylinder

 

[BrooklynBay]

Unplug the line with the engine running. See if there is vacuum. Your vehicle might stall, so you might want to keep the idle higher than usual. Have somebody hold the accelerator pedal lightly just to increase the RPMs above normal. Try to unplug the booster's valve before this test as was previously mentioned above. Do this test with the engine off.

 

[410Fortune]

Did you bench bleed the master cylinder before installing?
They do not bleed very well and sometimes not at all if it is not primed when you install it

 

[BrooklynBay]

The procedure for ABS is a little different than on a system without ABS. When you bled the system, did you do it at all 4 wheels? Sometimes you will get fluid in the front, but not in the back. There are different procedures depending upon your model, and year. Some require a special electric tool to cycle the ABS solenoid valve body. Other systems have a fitting on a part in the rear that you might call a diverter valve (it's not the same as the diverter on an ordinary system). I think rear ABS is just pulling the fuse.

 

[Afboy143]

Did you bench bleed the master cylinder before installing?
They do not bleed very well and sometimes not at all if it is not primed when you install it

I saw it in the book but I didnt bench bleed it, I just bled it regularly (Did the bleeding at all 4 wheels by connecting a line and hitting the brakes)

I just think it's weird that I have the same problem before and after. Should I try bench bleeding the master cylinder? Dont I need to buy some special parts?

 

[410Fortune]

Yes you need to bench bleed it.
You can get little plastic nipples that screw into the master and hook up to lines, you run the lines into the resevoir and pump the piston.
Many master cyl will come with those parts when new

 

[Afboy143]

thanks 410, that will be next weekend's task. If that doesnt work...what should I assume the problem. This is killin me