My brakes were completely fine, went in to my local Firestone for an alignment and just a brake inspection.. a week later my brake light come on and master cylinder is completely empty. I try to tell them they jacked sum up. They said no it’s a faulty master cylinder. I don’t believe in coincidences but they tried to charge me 300 for it. Did it myself today. Followed scottys video on how to bleed the cylinder solo. Every time I do it, the brake feels great.. then I start it. Lose all braking power as soon as it starts. Pedal goes from nice and firm after I bleed it to the floor. I know they messed something up but now it looks like I’ll be the trying to chase what they messed up. I don’t know what to do. I don’t trust mechanics so I wanna do it myself. Unfortunately it looks like I’m going to have to bite off more than I’m able to comfortably chew to fix this.
More details needed.
2006 Hyundai Sonata, 146k auto
You probably have a leak in your brake system that needs to be fixed. You did not provide any information on the type of car, its age, or its mileage. If the leak is at one or more of the wheels you'll see the inner side of the tire(s) streaked with fluid. However the leak could be in a failed brake hose or rusted out brake line. That needs to be determined by observation.
The leak might or might not be due to something they did. Seeing as how it took a week after servicing for the problem to surface it might well be a coincidence. However It's best in any event to stay away from chains shops like Firestone as well as dealerships and find a good independent mechanic.
Could a simple leak cause the brake to go from feeling really good to the floor right on startup? I’d assume that would have to be one mean ass leak considering it never had an issue leading up.
I should’ve added that I got them done on a Friday, last time it was used was that Monday then sat for week. On startup it was empty.
Are you losing brake fluid after you start it up? If so you have a leak. If not losing fluid and the pedal still sinks you probably got air into your ABS controller and need a professional-grade, bidirectional scan tool to bleed it. (Either that or your new master cylinder is leaking internally.)
Unfortunately, this is what happens a lot when you go to these chain places. A brake inspection is supposed to be a visual inspection of the fluid level and meat left on the shoes. They aren't supposed to do anything, like inadvertently empty your master cylinder to make more money for themselves. Did you request a brake inspection?
Who made the master cylinder you installed? Was it new or remanufactured? It could very well have an internal problem that's only showing with the pressure boost from the brake booster. I had this happen on my '79 Catalina last year with three different brake master cylinders from three different places. Either the rear seal leaked after bleeding or the pedal sank on start-up. Even an OEM MC was bad. The 4th MC was new from an AutoZone has worked thus far.
China made it
Alright so after changing my master cylinder out yesterday and having no luck I called it a day and came back to it today. I found the service manual for my car and decided to check my booster out. All the test went fine. EXCEPT. The one test that required me to have the engine running and me to hit the brake I immediately noticed white smoke coming from under the car (this is because someone sawed off my tailpipe in front of my cat but never finished the job, lived in Ga with no inspections so I didn’t have it fixed yet.. sue me) anyway, after replacing the MC I obviously still have fluid leaking into the vacuum from my booster. So do I have to replace my booster as well? Could this fix the fluid into vacuum leak and my still sinking brake pedal after replacing the MC? 06 Sonata, 146k
Please don't post multiple topics for the same problem. Thanks. (Topics merged.)
If fluid is getting into the booster then the master cylinder is leaking. The booster can be damaged over time. If it still holds vacuum it should be OK.
There may be no inspections where you live but you still better fix that exhaust leak before you get carbon monoxide poisoning.
So is the new master cylinder likely defective?
If it's leaking out the backside then it certainly is defective.
Yeah I guess. Just wasn’t sure if it could’ve been residual leakage from the older MC, guess I have china to thank for a bad MC. Looks like I’ll be getting an OE MC from the dealer for the fair price of 9k
Unfortunately new parts are commonly defective these days. It's a race to the bottom in quality with so much manufacturing moved to China. As @justin-shepherd reported he had three brand-new defective MCs in a row.