slow brake response

[Ceeker]

so I replaced the front calipers, brake booster and master cyl hoping that it would give me a better pedal, since it wasn't slowing the car down quick enough PERIOD. Unlike my other e30's, the brakes don't respond as quickly upon hard braking. it doesn't grab but gradually slows the car down under slow speed. 10-15 mph. I don't hear any vacuum leaks. I changed the fluid and thoroughly bled the brakes. changed the rotors and pads.

any idea?

[mlytle64]

did you cycle the air out of the abs?

[jlevie]

The only thing I can think of that would cause a slow application of the brakes for the same pedal effort would be an obstruction in the brake lines or ABS unit.

[LJ851]

What kind of brake pads are you using? Maybe they are really hard and don't bite well.

[bmwguy325is]

did you cycle the air out of the abs?

The only thing I can think of that would cause a slow application of the brakes for the same pedal effort would be an obstruction in the brake lines or ABS unit.

Bleed the brakes with the car running.

[Ceeker]

did you cycle the air out of the abs?

no I didn't and wondered about that. How does one go about doing so?

I will also try bleeding the system with the car running.

Using oem brake pads
thank you.

[LJ851]

no I didn't and wondered about that. How does one go about doing so?

Go for a drive and engage ABS a few times.

[mlytle64]

+1
bleed brakes.

go for drive. fully engage the abs from 50-60mph. all the way to a stop. repeat a few times.

bleed all the brakes again.

[Carib]

I'm thinking about doing the same as my brakes respond the same way as Ceeker described.

My question is regarding engaging the ABS at around 50-60mph... wouldn't you run the risk of warping the rotors if you slam on the brakes at that speed to get the ABS to work? Is there another way of bleeding the ABS system?

[jlevie]

A better way to get the ABS to engage, that will be easier on your brakes and tires, is to get on an empty and wet parking lot. 20-23mph is plenty of speed to get the ABS to activate if you really put your foot in it.

[5mall5nail5]

Hate to take it OT, but I was bleeding the brakes on our '87 325 yesterday using a BavAuto pressure bleeder. The right rear, left rear, and left front calipers bled fluid - not very fast, but fluid came out. The right front no fluid came out with 25 psi of pressure on the reservoir. I am assuming blockage some place - whats the best approach?

[5Toes]

Just guessing here... so dont take this seriously.

Maybe thread some weed whacker hose down that line?

[Ceeker]

Just guessing here... so dont take this seriously.

Maybe thread some weed whacker hose down that line?

that's actually not a bad idea... :-) desperate times call for desperate measures..LOL

[mlytle64]

I'm thinking about doing the same as my brakes respond the same way as Ceeker described.

My question is regarding engaging the ABS at around 50-60mph... wouldn't you run the risk of warping the rotors if you slam on the brakes at that speed to get the ABS to work? Is there another way of bleeding the ABS system?

absolutely zero risk of warping rotors or harming anything mechanical on the car. this is what the brake system was designed for. a couple of stops like this is also not going to wear out your brake pads or tires either.

the goal here is to have the abs operate for several seconds not just a quick brrrp. yes, if it is a rainy day this is an easier exercise as the abs comes on sooner. at the dealer they can turn on the abs and have the abs pump running while they are bleeding the brakes.

as a bonus, if you are not used to stopping this quickly or don't know what abs feels like, this is an opportunity to get familiar with what it does and what your car can do.

[jlevie]

Hate to take it OT, but I was bleeding the brakes on our '87 325 yesterday using a BavAuto pressure bleeder. The right rear, left rear, and left front calipers bled fluid - not very fast, but fluid came out. The right front no fluid came out with 25 psi of pressure on the reservoir. I am assuming blockage some place - whats the best approach?

This could be a blockage at the bleed screw, a blockage in the line to the caliper or a blockage in ABS module. The first thing to try is to crack the soft line at the caliper, then the junction of the soft and hard lines, and finally the hard line at the ABS unit. That will tell you where the blockage is.

As to the original post, air in the system results in a soft and spongy pedal. But the brakes will still stop the car normally with increased pedal pressure. "Slow brakes" would be those that do not fully apply as the pedal pressure is applied. That will be something that is restricting flow to the calipers.