Brakes real weak unless pumped a few times

[Psych0matt]

So my brakes in the sedan are annoying the crap out of me. A few weeks ago they seemed to be getting worse as it was getting colder, and didn't think too much of it because of the age, and temps. Well, it started getting to where I felt it unsafe, so I topped it off because it was a bit low, and it was fine for like a day. Both before I topped it off and after, it seems as though my brakes barely work, unless I pump them a few times coming up to where I need to brake, and if I do so they seem fine, but then next time I have to stop I have to do it again. Maybe I sucked air in and need to bleed them? any other thoughts?

[Addicted To Boost]

Booster going bad?

[Psych0matt]

ahh, that could be too! I've never done any brake work up by the booster, so I don't know what kind of symptoms I'd have.

[AL]

The booster usually makes for a really hard pedal... Like braking when the car is off... If your fluid was low, it may be leaking out somewhere and thats where you are losing your pressure

[94 olds vert]

That's how my brakes felt before I swapped them. I thought they were supposed to feel like that.

[urbex]

I know whenever I have to move the car it feels like I'm going to crash into something because I have to push the brakes so hard and it doesn't do shit...

[kinger_13]

It sound like your Master cylinder is on its way out. I had this problem on an older vehicle once. If you pump the brake pedal and hold it, is there pressure first and then it goes down? If so I'd say Master cylinder.

[Cutlass350]

Did you loose any brake fluid after you topped it off?

If not, it's the Master Cylinder.
If you lost fluid, check the calipers, hoses, and brake lines for leaks.

A bad booster makes the brakes hard.


Make sure you use a good flare wrench on the fittings on the brake lines. Otherwise, you can round off the fittings. A cheap flare wrench can also round off fittings. For really tough fittings, I carefully use the vise grips made specifically for use on nuts.

Good Luck!

[Brian P]

x2 on checking the calipers first, including the sliders/pins too since that could create a similar effect. Given your sedan is a '91 I'd check the rears before anything else.

[Schurkey]

Poor braking power with

Low, squishy pedal = hydraulic problems especially air in the hydraulic system, but could be defective seals in the master cylinder.

High, hard pedal = defective booster or seized calipers. Possible ABS problems, but not as likely.

Both my '92 and my '93 had defective boosters. Neither has had defective calipers in the time I've owned them (bought '92 in November, '92; bought '93 about 5 years and 40,000 miles ago. I think the reputation for seized rear calipers is exaggerated--but I acknowledge that my sample size is pretty small.

[Cutlass350]

Both my '92 and my '93 had defective boosters. Neither has had defective calipers in the time I've owned them (bought '92 in November, '92; bought '93 about 5 years and 40,000 miles ago. I think the reputation for seized rear calipers is exaggerated--but I acknowledge that my sample size is pretty small.

Plus, it's easy to verify a bad booster. Remove the vacuum line at the check valve, plug the vacuum line with a bolt to prevent a vacuum leak, and see if there's any difference in the brakes. On my Intrigue, when the booster went, it also caused cylinder misfires because of the vacuum leak. BTW, when I plugged booster vacuum to verify a bad booster, it also got rid of the cylinder misfires.

For my Intrigue, doing a booster R&R means fully removing the ABS/TC unit.

Old Booster removed, ABS removed, EGR valve removed:



New Booster, ABS (right), EGR valve(left) installed:

[Psych0matt]

I'll have to check some things out tomorrow, maybe I can convince Eric to help me out. Food is a good negotiating tool

It seems to hold pressure just fine when stopped, but I have to pump it again shortly after if stopping again. I do have a rotor or caliper messing up as well, but I don't think it's really related, just time to replace it anyways

[Schurkey]

Plus, it's easy to verify a bad booster. Remove the vacuum line at the check valve, plug the vacuum line with a bolt to prevent a vacuum leak, and see if there's any difference in the brakes. On my Intrigue, when the booster went, it also caused cylinder misfires because of the vacuum leak. BTW, when I plugged booster vacuum to verify a bad booster, it also got rid of the cylinder misfires.

Neither of my boosters leaked vacuum or caused misfire. Both boosters had "some" assist--the '92 had a bit more than the '93, but neither had PROPER, FULL assist.


Truth is, I didn't know a booster could fail that way--to simply have reduced power assist without vacuum problems--but I'm two-for-two.

[AL]

It sounds like a bad master cylinder because its not sending the proper pressure to the wheels

[brake]

Did you bleed the brakes or just dump new fluid in ontop of the old stuff?