Brake problems... (Update)

[redzmonte]

Brakes all worked as expected just needed new pads in front because they were getting thin. So i compressed the front calipers and replaced my front pads. one side was a little stubborn but it did eventually compress and i was able to swap pads. I did not remove any brake lines. after the pads were on i pumped them up and went for a drive. The pedal gets nice and firm when pumping them up with the car off. Once i turn the car on the booster pumps up and the brakes become VERY soft and spongy. I replaced the master cylinder and bleed the brakes Front and Rear with the pump and hold 2 person method until all the fluid was clean and no air bubbles spitting out. Same results spongy. Did a gravity bleed for 10 min per caliper and same thing. I also checked the check valve and brake booster, both appear to be working correctly.

If I didn't get the master cyl bench bled properly could that still have air in it even after bleeding the brakes at the calipers? What else would cause the brakes to be spongy? Something in the ABS Pump bad? Bad original master and Defective replacement out of the box? (does happen but it feels 100% the same as the original that i just replaced....)

Glad to hear any good ideas..

Shane

[96 SSEi]

hi' I would bleed again from the farthest to closest with engine running- so rr then lr then rf then closest to MS lf - make sure the master doesnt run low and check the booster vacuum line for leaks - the thick vacuum line from top of throttle body to round booster on firewall

[MKMike]

How was the pedal before you worked on the brakes?

First check every connection carefully for any leaks.
Brake fluid rinses off with water, so you can rinse off any suspected leaking connection, blow it dry or wait for it to dry and then pump the brakes repeatedly or take it for a ride.
ANY leak will cause air to enter the system and fluid to leave it.
If the brake fluid level in the master cylinder reservoir got too low during bleeding, it will have sucked air into the system..
If you did not bleed the master before installing it in the car or did not bleed all of the air out of it, that's can be the problem.
You can crack open the fittings at the master to bleed it, the same way you do with bleeder screws.
The master has to be bled before the rest of the system gets bled.
If you somehow got air into the abs unit, you'll have to find some gravel and apply the brakes hard so the ABS activates to move the air out of it. (Unless you have a Tech 2.)
Then, re-bleed the system.

Low vacuum to the booster results in a very hard pedal.

[DCJREDLINE]

I would inspect that "stubborn" caliper more. Maybe you blew the seal on that one trying to compress it. That is about the only thing that I see would cause your soft pedal problem after just a pad change.

[redzmonte]

I have bleed them a couple times now... Pump and hold and gravity bleed. Furthest to closest. Both feel the same. I did check the booster hose and all appears to be good, including check valve. Brakes worked great before I started... I will try the master cyl bleed again. I did order new calipers for the front. Lol got the ricy red powder coated ones from rock auto should be here wed, so I will try it all again. Mechanic also suggested bad seal in caliper but no external leaks. I checked many times and all is bone dry.

Good news is it forces me to drive my Z06 for the week while I got the Bonnie ripped apart :D

[ddalder]

It's entirely possible you still have air trapped in the ABS modulator. The only effective way to bleed this is using a scan tool. Other methods can shift the air around a little but actually getting it out is another story. The service manual does say specifically that if you open the braking system upstream of the ABS modulator, you need to complete the automated bleed process. It is possible that you may not have introduced air upstream, but if you've tried everything else, this is where I'd be looking.

[DCJREDLINE]

Before my Bonne finally died I had to replace two of the lines that go from the MC to the ABS module. Even doing that I did not have to go through the scan tool bleeding procedure. Id be shocked if opening a bleeder screw would cause you you have to scan bleed the ABS module. It is possible but I think unlikely.

[ddalder]

I was also a little suspicious about the caliper that was difficult to compress, but it's conceivable that there's more going on than just that. Either way, as soon as the lines are opened up before the ABS module, anything is on the table in regards to air in the system. The caliper definitely requires some further attention though.

[redzmonte]

Swapped calipers and made a good difference. still feels a little faint, but I think that is just the pads I put on (wearever Platinum's) they don't bite like the others I had before. here are a couple pics.
Before: (spray painted black)



After: Very Red, look pinkish because of the portable light I had turned on

[Jrs3800]

Just curious.. Are those Power Stop Rotors?

[redzmonte]

Just curious.. Are those Power Stop Rotors?

No complaints, I've had them two sets of brake pads no worping.

Here are the calipers straight out the box

[ddalder]

Calipers look nice

[redzmonte]

they seem to be good quality parts. They came with hardware and new slide pins and all. coating seems to be a good quality job as well. Only problem I can see is that they only sell in pairs so if one fails you will need to buy both again... luckily they are cheap $26 ea + shipping and $10ea core.. so heavy its not worth the money to ship cores back. If I needed rotors as well I would have just done a Corvette/Fbody swap... they come coated red as well and are dual piston with larger rotors.

S