I was driving today and my brake pedal suddenly got very stiff, like the power booster no longer had vacuum. Once I stopped, I checked for vacuum and everything appeared normal. I pulled the vacuum valve out of the brake booster and heard a hiss, suggesting another problem. To make matters worse, I dropped the grommet that holds in the vacuum valve and it did not come out the bottom. It was too dark in the parking garage for me to see it and I didn't feel like reaching for it around a hot header.

No lights came on so I assume it is not an ABS problem. Does anyone have any ideas?

Thanks in advance.

 

My guess is your Power brake booster is shot.

 

That is what I am thinking also. I did get more info. On my way home today I heard hissing coming from the floor board every time I hit the brake pedal. I know very little about power brakes so I don't know what it could be.

If it is the power booster, how hard are they to replace? Also, should I replace the master cylinder when I do it? How much do power boosters cost?

 

There is a ton of detailed info here on replacing the booster. (do a search or check the tech tips)
Remove the knee bolster under the dash
Remove the master cylinder- you do not have to remove the brake lines - and move it out of the way
Remove the vacuum line to the booster
Now for the fun stuff! Be a bit of a contortionist and have some patience.
Find and remove the clip that holds the pedal to the booster plunger.
Remove the four nuts that hold the booster to the firewall. These are tricky and you will need to use swivels, extentions and whatever you find that you feel comfortable with using to remove them. Try not to drop them 'cause they'll go where ever you cannot reach.
After the nuts are removed, the booster slids out.
Replacing the booster can be a bit of a challenge if the brace under the dash is not lined up with the holes in the firewall. Patience must prevail here (don't ask me how I know)
Make sure you get the plunger on the pedal when you slide the boosterin (don't ask me how I know this either)
Replacing the nuts is a bigger pain than taking them off, especially the 2 on the right side. If you don't have a magnet that fits inside the socket, try a bit of heavy grease to hold the nut in place. Again, use anything that you feel comfortable with to get the nuts on.
Now that a few hours and a few beers have passed, tighen everything under the dash, replace the plunger/pedal clip, replace you knee bolster, attach the vacuum line and replace the MC.
Good luck
Subman