Spongy Brake Pedal? Check Your Hydraulic Brake System

Had the exact same issue with my 2018 Chevy Suburban Diesel. The spongy brake pedal was concerning, especially since I have some experience working on brake systems. The problem turned out to be worn brake lines and contaminated brake fluid. The warning light came on shortly after I noticed the pedal getting soft. My mechanic did a complete brake fluid replacement and found several deteriorating brake lines that needed replacement. Total repair came to about 480 for parts and labor, definitely worth it for safety. The brake pedal is now firm and consistent. What's your current mileage? Have you noticed any brake warning lights? This could help determine if you're facing the same issue. Also, when was your last brake fluid change? These details would help narrow down the problem. If you're getting that spongy feeling, don't wait too long to have it checked. Brake system issues usually don't improve on their own.

Thanks for sharing your experience. I'm at 111063 KM and just had service last month, though they didn't specifically check the brake system. Your description matches my symptoms exactly, especially that spongy brake pedal feel. Interesting that you mention the brake lines, as I haven't had those inspected yet. No warning lights so far, but that inconsistent pedal feedback is definitely concerning. A brake inspection seems like the smart next step, especially since these symptoms sound identical to what you experienced. Going to schedule a brake fluid check and line inspection first thing. Rather be safe than sorry when it comes to brake issues.

Yeah, sounds like you're making the right call getting it checked. After my brake line issue, I learned it's pretty common in these models around 100-120K. The master cylinder and brake lines can develop tiny leaks that aren't obvious at first. What convinced me something was wrong was that inconsistent pedal feedback, exactly like what you're describing. The brake inspection revealed hairline cracks in two brake lines that were slowly letting air into the system. No warning light at first, but it would've gotten worse. Quick tip from my experience: have them check the master cylinder seals while they're at it. Mine were starting to wear too, and replacing them during the same service saved some labor costs. The whole brake system works better when all components are in good shape. The fact that you're getting the same pedal feel I had, at similar mileage, really points to brake lines or master cylinder issues. Better to catch it early before any warning lights pop up.

Thanks for that detailed information about the master cylinder and brake lines. Makes total sense about getting everything checked while they're in there. My symptoms are matching up with what you've described perfectly now, that inconsistent pedal feedback was really bothering me. Just booked the brake inspection for tomorrow morning. Mentioned the potential brake line and master cylinder issues to the shop so they know what to look for. The mileage similarity and identical symptoms have me convinced this could be the same problem. Really glad I asked about this before the hydraulic brakes got worse. Good tip about checking the seals too, will definitely have them inspect those. The brake pedal definitely shouldn't feel this spongy, and I don't want to risk driving it much longer without getting the brake system thoroughly checked. Better to find and fix any issues now than wait for potential brake failure later.