Spongy brake pedal is alarming, and you are correct to question why they suddenly feel spongy. But no need to be alarmed, I’m a mechanic, and the fix is a simple one.
Silverado brakes will commonly feel spongy until the new brake pads bed in. Driving the truck and braking normally five to six times will restore brake pedal feel.
In this post, you’ll learn why your Silverado brakes are spongy after a pad change and what you can do to fix it right now.
Spongy Brake Pedal Feel
Brakes are serious business, and for sure, it’s a component we can’t ever take a chance with. A spongy brake pedal after replacing the pads is disappointing but is actually common.
The reason the brake pedal feels spongy is that the new brake pad surface hasn’t yet mated to the surface of the brake rotor. Your truck’s rotors, while flat, aren’t completely flat; the surface is somewhat irregular from normal wear and tear.
The new perfectly flat pads tend to ride across the high spots of the rotor, and that allows for flex when the brake pedal is applied. This flex is what causes the unwanted spongy brake pedal feel.
This is normal when new pads are fitted, and the fix is simple, and that’s exactly what we’ll cover next.
Silverado Spongy Brake Pedal Fix
The fix of a spongy brake pedal after a new set of pads is super simple. – Take the truck for a drive and brake normally five to six times.
This is a job every technician must do after replacing the brake pads. Otherwise, the brakes are compromised.
Ideally, the truck should be driven on a quiet road for the brake bed-in process. The process looks like this:
- Pump brakes several times before moving the truck – this ensure pads are at the rotors
- Check the brake fluid reservoir level and top up if necessary
- Drive the truck at 20 MPH and brake normally (repeat twice)
- Drive the truck at 40 MPH and brake normally (repeat twice)
- Drive the truck at 60 MPH and brake normally (repeat twice)
- Drive the truck at 60 MPH and brake sharply (repeat twice)
- Assess brake pedal feel and repeat if necessary
- Finally, recheck the brake fluid level
I avoid braking hard on new pads initially, as it can damage them. Bedding in brakes isn’t really a job you can mess up, and you shouldn’t sweat the details; just drive your truck normally, brake normally, and the brake pedal will improve.
Mechanics Brake Fitting Tips
Brake repairs are a serious business, but not beyond the DIY home mechanic. Mostly mechanical repairs and maintenance are just old-fashioned common sense.
Anyhow, I’ve been a mechanic for over twenty-five years and have done a ton of brake repairs. Here are my top tips for brake jobs that move like butter.
- Use axle stand to support chassis
- Wear dust mask
- Use plain water in water to spray down brake dust
- Use a wire brush to brake carrier
- Use anti-squeal paste on pads
- Use silicone grease around rubber components
- Use copper grease on wheel hubs
- Torque wheels in star formation
- Torque wheels to spec
- Pump brakes several times after fitting the pads and before moving the vehicle
Other Possible Causes of Spongy Brake Pedal
If your pedal doesn’t improve with the bed in process as per above, then we may have another issue. We’ll cover the other possible causes in this section, how to diagnose them and how to fix them.
Warped rotors commonly happens as rotors wear and get thin. The heat rotors naturally produce when braking causes them to buckle. This has the effect of pushing the pads further away from the rotor, which means the brake pedal must travel further to apply the pads. This creates a spongy brake pedal feel.
Diagnosis – This commonly causes a pulsating or vibration felt in the brake pedal when braking.
The Fix – A tool may be used by a technician to check runout, and if the rotors are within spec, they may be turned to remove the buckle. That said, it is often better to just go ahead and replace both rotors. Always best to replace braking components on the same axle in pairs (both front and back).
Air in brake system
Your Silverado brakes are powered by hydraulic fluid, and the system won’t tolerate air in the system. In a healthy system, as you press the brake pedal, the fluid is pressurized, and as it doesn’t compress, it pushes out the pistons on all four brake calipers.
In a system contaminated by air, pressing the brakes causes the air bubbles within the fluid to compress, allowing the pedal to sink further to the floor before eventually activating all four calipers – a spongy brake pedal.
Diagnosis – The best way to diagnose is to go ahead and bleed the brakes and see if that helps our brake pedal feel.
Fix – Bleed the brake system. Bleeding the brakes may be performed easily by the DIY mechanic. The process is as follows:
- Pop hood and check brake fluid reservoir level
- Prepare the bleed kit by ¼ filling catch bottle with fresh fluid
- Start by removing the right had rear wheel
- Remove the rubber bleed valve cover and wire brush the bleed valve threads
- Apply some grease to the threads, attach box wrench and bleed hose
- Open the bleed valve one turn
- Pump brake pedal three times
- Inspect the bleed hose for bubbles, if you have bubbles, pump pedal again until free of bubbles
- Hose bubble free tighten bleed valve, clean, refit valve cap and top up the reservoir before moving to the left hand rear wheel and repeating the process.
- Top up fluid and now move to the right hand front
- Top up fluid and move to the drivers front
- Check and adjust the fluid level
Contaminated brake fluid
Brake fluid is hygroscopic, which means it naturally attracts moisture as it ages (unless your brake fluid is silicone-based DOT 5).
And moisture in your brake lines is bad for two reasons:
1 – It causes a spongy brake pedal feel. As your rotors work, they produce heat, and that heat causes the moisture within the brake lines at the caliper to boil and turn to steam. As steam is compressible we get that horrible spongy brake pedal feel.
2 – The moisture within the brake lines attacks the metal components of your system, caliper pistons, and ABS modulators – all expensive kit to replace.
Diagnosis – Typical symptoms of moisture-laden brake fluid is a normal brake pedal feel when the brakes are cold but becomes spongy when brakes are used a lot. If your brake fluid is three years or older, go ahead and change it out. Brake fluid attracts about ///////% of moisture every year.
The Fix – Go ahead and flush the brake system and replace the fluid. You may flush the brake system and replace the fluid in the same way as bleeding the brakes. The difference is you’ll bleed each brake caliper for longer, and you’ll refill the reservoir at least twice to push out the old fluid.
A spongy brake pedal commonly occurs after new brake pads are fitted. The perfectly flat surface of the new brake pad will cause a spongy brake pedal feel until the pads mate with the slightly irregular surface of the rotors.
Driving the vehicle normally and braking normally will mate the pads rotors and will restore the brake pedal feel.