Spongy Brake Pedal

MA87K5 · May 26, 2009

I have a spongy pedal after I replaced my pads on a 99 tahoe. So I bled the calipers. Broke a bleed valve on one so I got new calipers. Bled them. Still spongy. Got new master cylinder. Bled it. Still spongy. What am I missing? What went wrong? Thanks. I have no bubbles at all when I bled the brakes. Used a big bottle of fluid.

bossier62guy · May 26, 2009

I have a spongy pedal after I replaced my pads on a 99 tahoe. So I bled the calipers. Broke a bleed valve on one so I got new calipers. Bled them. Still spongy. Got new master cylinder. Bled it. Still spongy. What am I missing? What went wrong? Thanks. I have no bubbles at all when I bled the brakes. Used a big bottle of fluid.

Are you sure you have the calipers mounted correctly? I had a friend of mine replace the ones on his Mustang a few years back and he mounted them on the wrong sides w/ the bleed valves down....never could get all the air out of them. Took a local mechanic to help us pull our heads out of our rears on that one. Just a thought....

Draenor · May 26, 2009

You replaced the master cylinder, was the brak booster change? How about the brake hoses?

It is typical GMT400s to get a spongy brake pedal.

426ted · May 26, 2009

I have a spongy pedal after I replaced my pads on a 99 tahoe. So I bled the calipers. Broke a bleed valve on one so I got new calipers. Bled them. Still spongy. Got new master cylinder. Bled it. Still spongy. What am I missing? What went wrong? Thanks. I have no bubbles at all when I bled the brakes. Used a big bottle of fluid.

Rich, did you bench bleed the master cylinder?

MA87K5 · May 27, 2009

I bled the master cylinder on the truck with the plugs in where the lines would go and had someone push the brake pedal till no more bubbles came up in reservoir. Nothing else was changed. Brakes were fine before I put new pads in. Got the spongy pedal after new pads were put in. Can there still be air in the abs controller?

tramz · May 27, 2009

Did you bleed the rear?

ukrkoz · May 27, 2009

I bled the master cylinder on the truck with the plugs in where the lines would go and had someone push the brake pedal till no more bubbles came up in reservoir. Nothing else was changed. Brakes were fine before I put new pads in. Got the spongy pedal after new pads were put in. Can there still be air in the abs controller?

aren't you supposed to have lines running back INTO the master when bench bleeding it?

anyhow, you might be chasing ghosts. GM does have spongy pedal feel. i always have mine double distance from a car in front of me. it is complaint of many....

i just have that feeling that - as you have never said what it felt like before - you had stiff pedal, which is obstruction in the line somewhere, then you fixed it unintentionally, and now you have "the correct" feel, it just does not feel right.

MA87K5 · May 27, 2009

the rear was bled. The pedal wasn't spongy at all before the pad change. When I started to push on the pedal I could feel the brakes start to grab. Now it's almost at half pedal when the brakes start to grab. Not good. I followed the instructions that came with the master cylinder.

txab · May 27, 2009

the rear was bled. The pedal wasn't spongy at all before the pad change. When I started to push on the pedal I could feel the brakes start to grab. Now it's almost at half pedal when the brakes start to grab. Not good. I followed the instructions that came with the master cylinder.

You said earlier you bled the MC after it was mounted on the truck. The directions say to bench bleed it first. You may not have been able to stroke to the depth needed while mounted on the truck to properly bleed it.

MA87K5 · May 27, 2009

I believe that the bench bleed is for one person. I had help to bleed it. This weekend I'll bench bleed it to see if I am correct. I never had to bench bled a mc before out of all the ones I have changed. Never had this problem with them.

MA87K5 · May 31, 2009

I went to the parts store and compared the ceramic pads with the semi-metalic ones. (I forgot to mention I changed to ceramic pads.) The contact patch for the semi-metalic pads are much more then the ceramic ones. Going to go back to the semi-metalic ones tomorrow. Let u know if that fixes it.

MA87K5 · June 2, 2009

Changed the pads. Glad I did, the pads were cracked along the side. After that I did the back yard mech way of clearing the abs of bubbles. Went down a dirt road and slammed my brakes. Did that a couple of times and the pedal feels alot better. Just need to bleed to get the rest of the bubbles out if any. The MC bench bleed is for one person but 2 can bleed MC on the vehical.

jblakeney · June 2, 2009

Sup,

NAPA Jobber here. I would protest the 2 people can do it on the vehicle. Yea 2 people can do it on the truck.... But it is hard to remove all air from a new master cylinder on the truck. The master cylinder needs to be put in a vise and bleed PRIOR to putting it on the truck unless you have some sort of brake bleeding machine such as a Vacula (http://usa.vacula.com/newsite/produkter/pr...hp?product_id=5 there are several different brands of bleeders also www.brakebleeder.com) brake bleeder or a some sort of pressurized brake bleeder. You WILL NOT GET FULL STROKE on the cylinder on the TRUCK only some of it. This keeps you from bottoming the pulnger out in the cylinder on a normal basis which will cause it to start leaking. Also, anything over 5 years OLD NEEDS ALL NEW BRAKE HOSES (brake hoses decay from the inside out so they look good but they might not be). You would be suprised how much that will help in pedal feel..... FYI BLEED NEW MASTER CYLINDERS OFF THE TRUCK, then bleed right rear, left rear, right front, left front....... Keep check on the fluid and make sure the master cylinder does not run dry during the bleed or START OVER. Or take the Tech2 or Genisys and start the brake bleed procedure from the scan tool.

I get this phone call on a regular basis, that BLANK (master cyclinder, wheel cylinder, caliper, clutch master cylinder, clutch slave cylinder, or hose) part you sold me does not work, I have bleed it and bleed it and it is still not working.... After a 30 minute phone call of me running down what the guy is doing I usually end up hearing something like I did it on the truck not off the truck....... In this case. or in the clutch case I am pumping it about 10 times then holding and releasing the bleeder......... Anywhooo that turned in to a ran sorry.....

Oh yeah, you probably got the spongy pedal when you pushed the piston back into the caliper... You PUSHED the trash out of the caliper back into the hose and its clogging your HOSE!!!!!............. Before you even pull the caliper off the truck flush some brake fluid threw the system...... It will keep your fluid cleaner and the trash from clogging your hoses...... Trash will collect in the caliper and sit and wait on you to push that piston back and then WHAM calipers start sticking and hoses are clasping.

Jbo

MA87K5 · June 2, 2009

Maybe you are right. Then the 100's of brake jobs I've done I've been lucky. I've never had this problem before. Thursday I'm going to redo the mc off the truck if I still have the plugs. If it works then that's one more thing I learned. Learning is always good.

low05crewcab · June 30, 2009

Maybe you are right. Then the 100's of brake jobs I've done I've been lucky. I've never had this problem before. Thursday I'm going to redo the mc off the truck if I still have the plugs. If it works then that's one more thing I learned. Learning is always good.

Would suggest bleeding the mc off the truck,not saying the two man approach doesn't work,just going off my years as a professional GM tech. Might be a good idea to flush the system just in case some trash got pushed back and clogged somewhere in the system. Hope this might help with your truck.