2003 Tahoe Pedal Spongy After Front Pad Replacement

[Puhdantic]

I took the cap off the MC, then squeezed the pistons back in. After that, I put the new pads on.

Now when I push the brakes they're spongy with the car on but more firm with car off. I keep reading that there's air in the system, but I don't get how I could have introduced air if I never opened the bleeder screws.

 

[zrxkawboy]

Why not try bleeding them to see if it helps?

 

[JohnnyG]

Have the brake fluid changed and see if that fixes it. A little more info would be helpful. Like, when was the last time the brake system was flushed. You know, little things like that would help a lot.

 

[Puhdantic]

Have the brake fluid changed and see if that fixes it. A little more info would be helpful. Like, when was the last time the brake system was flushed. You know, little things like that would help a lot.

It's been a very long time since they were flushed. Maybe 6 or 7 years

 

[Gyro Gearloose]

I'm not a mechanic so my knowledge on vehicles and parts is spotty, but at least SOME of the GM trucks I've owned (MY 2003 - 2010) and SOME of the brake pads I've installed on those vehicles had different pads for inners and outers and they can't be swapped. The outer pads had 3 little bumps on the back to position the backing shim while the inner pads were either smooth or had bumps that would land in the center of the pistons. Can't remember exactly. But if you mix them up one of the bumps on the outer pad will land right on edge of the piston and that limited contact area with the piston will make the brakes feel spongy.

 

[slacktide_bitog]

Speed bleeders are awesome

 

[Chris Meutsch]

I'm not a mechanic so my knowledge on vehicles and parts is spotty, but at least SOME of the GM trucks I've owned (MY 2003 - 2010) and SOME of the brake pads I've installed on those vehicles had different pads for inners and outers and they can't be swapped. The outer pads had 3 little bumps on the back to position the backing shim while the inner pads were either smooth or had bumps that would land in the center of the pistons. Can't remember exactly. But if you mix them up one of the bumps on the outer pad will land right on edge of the piston and that limited contact area with the piston will make the brakes feel spongy.

This is fascinating. I had no idea that pads may be side-specific.

 

[wpod]

Pad material or pad contact.

 

[clinebarger]

The Pads have to "Bed-in".

 

[Puhdantic]

Why not try bleeding them to see if it helps?

I bled all wheels and it seemed pretty firm after finishing. Once I started the car, the spongyness returned.

People are mentioning bedding. If I get this spongyness wouldn't it be really dangerous to try to bed them since the brakes may not be applying?

 

[D60]

Is this hydroboost or vacuum? The former always feels a bit spongy, I'm wondering if that combined with a different pad compound is, well, compounding.

Why would it be dangerous to bed them? Just do it on a quiet road....? The rudimentary procedures I follow don't take you above 45mph

 

[Puhdantic]

Is this hydroboost or vacuum? The former always feels a bit spongy, I'm wondering if that combined with a different pad compound is, well, compounding.

Why would it be dangerous to bed them? Just do it on a quiet road....? The rudimentary procedures I follow don't take you above 45mph

It's a vacuum booster.

I asked about the bedding since If it's spongy doesn't that mean brakes aren't applying at all?

 

[D60]

It's a vacuum booster.

I asked about the bedding since If it's spongy doesn't that mean brakes aren't applying at all?

I suppose from afar we don't know just how spongy you're talking -- or at least I don't. Is the vehicle not slowing at all when brakes are applied?

 

[edyvw]

What pad brand did you use?
Pad material is very important. If your old pads were semi-metallic and now you used ceramic, yes, pedal will be softer.

 

[Puhdantic]

I suppose from afar we don't know just how spongy you're talking -- or at least I don't. Is the vehicle not slowing at all when brakes are applied?

The car actually seems to stop ok when driving. I do notice a woosh noise is still there when braking.

Is there a way to tell if the rear brakes are doing more work than the fronts? I just got a feeling the problem is concentrated near the front.

 

[D60]

The car actually seems to stop ok when driving. I do notice a woosh noise is still there when braking.

Is there a way to tell if the rear brakes are doing more work than the fronts? I just got a feeling the problem is concentrated near the front.

At the risk of stating the obvious if the woosh is under the dash you've got a vac booster leak. Typically this will make for a hard pedal because power assist is reduced or eliminated but I suppose on certain systems it could make the pedal feel spongy.

As for trying to determine f/r bias....I suppose if it were me I'd get on a dirt road and hit the the brakes with varying degrees of severity until I just got lock-up (or likely ABS engagement) and see which wheels appear likely to lock first. Far from perfect for a number of reasons but if there's considerable bias to where the fronts are doing less work than the rears it should be easy to find on a dirt road.

Still, if you think the fronts aren't working properly I'd start with a healthy bleed, esp on that circuit. OTOH exercising the ABS pump may help bleed it if air somehow got in there...

 

[meep]

1. If the rotor surfaces aren’t perfect, you won’t get full contact until the pads bed in.

2. This will exaggerate any differences in pad material and pedal sensation.

3. How old is the fluid? Is it clear? If it’s old, the worst stuff collects at the bottom, and it just got pushed up into the rest of the system. This shouldn’t change the feel of it, however, but is worth mentioning - consider it a wild card.

4. I’ve not noticed it in smaller cars, but in my f150, pads do have different pedal feel. Element3 / eht pads from raybestos have a far firmer pedal feel than the oem stuff. I don’t like a soft pedal.

5. Do you have a 2 stage brake booster? Depending on how those are set up, the second stage can contribute to the soft feel.