kgkern01

When I hit my brakes, occasionally it will feel "softer" and the brake light will come on, then another tap of the brakes and it firms up and the light goes off. What could cause this problem?

Jeff94TA

A few things come to mind:

Brake booster on its way out
Air in the lines
Badly contaminated brake fluid

I assume that you have checked the fluid level and it is topped off. If you've never flushed the fluid that would be where I would start. This will take care of any air in the lines and get rid of the old fluid. If it still persists after that then I would say booster. I'm also assuming that you've checked for leaks and everything is dry. Just my thoughts anyone else?

TA Dreaming

i agree. check the lines and fluid level first. flush the system anyway. if youve never done it, it needs it. one way to check the booster is to pull the vacum line off of it after youve driven it or cranked it. if air doesnt suck into it then its not working right. Trey

kgkern01

So, if air doesnt suck into the booster -or- the vacuum line (which one) then the booster isnt working right? Is a booster expensive/hard to replace?

mitchntx

It's a PITA ... at least on an LS1 equipped car. I had to remove a valve cover in order to get it out.

The booster has 2 studs that stick through the firewall and are undone from inside the car.

kgkern01

How do I check for sure if it is the brake booster? About how much do they cost?

Jeff94TA

Bleed the brakes first to make sure that is not the problem. Keep bleeding them until you get clear fluid coming out. This will require at least one large bottle of brake fluid but it's cheap and easy compared to the booster. Start with the wheel furthest from the master cylinder and work your way to the closest wheel. I do right rear, left rear, right front and then left front.

I looked on carparts.com and they list a Bendix brand booster for $162.50.

EastLa

I replaced mine not too long ago, I had had your problem and blead my brakes several times with no luck in fixing the problem.

I had to remove the driver's side valve cover, unbolt the abs unit, and the master cylinder. It was really harder to get out than in. The 4 nuts under the dash (2 of them) are the hardest things to get to.

I think I paid $70 for mine from AutoShack...err Zone...

I had the thing swapped out in about 3 hours total with no help.

kgkern01

Well, yesterday I noticed a slight amount of brake fluid where the master cylinder attaches to the brake booster. Does this mean that the problem may be the master cylinder? I haven't yet had a chance to bleed the brakes.

chuck

It could also be a stuck/sticking caliper. If the brake light is coming on, I beleive that means there is an unacceptable difference in pressure between the front and rear circuit.

I agree with bleeding the brakes first, although I doubt that is going to solve the problem. It is just time to do it, and will eliminate the possibility.

Next I would take the car for a drive and put a little (emphasis on little) heat in the brakes. Then check to make sure all four rotors are warm. An infrared pyrometer is valuable here. Sears has them for ~$50.

Next I would pull each caliper, and clean and lube the guide pins (the ones that the caliper bolts go into) that go in the abutment bracket. Make sure they move freely, and that when gently pushed in the "spring" back out from the pressure of the rubber/grease. If any of the pads are thin this would be an excellent time to replace them.

I would not think a failing booster would cause the brake light on the dash to come on.

kgkern01

I'm finally off work today and it is warm enough to mess with the car. I look under the hood to check the brake fluid, and it is leaking where the master cylinder meets up to the brake booster. Not a lot, but there is some fresh fluid there. Could this be due to whatever problem I am having? Would this leak be caused by a bad master cylinder or brake booster or other? Someone let me know so I don't buy the wrong thing. Would this cause the soft pedal/brake light condition previously mentioned? I am having to hit my brakes twice to get them to get some good stopping power/firmer pedal.

mitchntx

DEFINITELY a master cylinder will cause all the problems you've listed

kgkern01

So basically if I get a new master cylinder, then of course re-bleed the brakes, that should fix it then, right? Looks like I may be doing this on Friday. Is the LS1 master cylinder any better/different? If it is better, can it be used in place of my LT1 part interchangeably without problems? Just wondering.

TA Dreaming

you will need to bench bleed the new master cylinder before putting it on. there should be instructons on how to do that with the new MC. if not do a search it should come up some where.

kgkern01

I know I will need to bench bleed the new MC, I was just wondering if the LS1 MC is any better than the LT1 and if so, are they interchangeable.