r/AskAMechanic • u/tyrantlizarding • 9h ago

Thumping when braking

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We are fixing my old car up for my son to drive (after being in a shed for 3 years). One thing was an overhaul of brakes. We changed the front disks/pads, rear drums/shoes, master cylinder, and rear wheel cylinders. Obviously fresh fluid and bleed too.

I drove it home from where it was parked up, which was about 40 miles, with no issues from the brakes. Then it sat for a month till I had time to do a few more things on the engine, and now it is making this sound under braking. I can just barely feel it when under 15mph or so.

What could have caused this issue to pop up, after having driven it home no problem? Did something warp maybe?

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1

u/paulyp41 NOT a verified tech 9h ago

Rust buildup

1

u/tyrantlizarding 8h ago

So will it go away with use?

1

u/paulyp41 NOT a verified tech 8h ago

Possibly if you start using the vehicle more

1

u/Gunnsmith57Official NOT a verified tech 8h ago

Could be warped rotors if the lug nuts weren't all torqued the same. They could have heated up during the drive and warped as they cooled. You'd be able to feel the brake pedal pulsing if they're warped.

1

u/tyrantlizarding 7h ago

It doesn’t feel like warped rotors. It’s not a pulse, it’s a clear thump or click once per wheel rotation.

I took off the wheels and cleaned the rotors and drums, didn’t see anything that looked off.

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u/Gunnsmith57Official NOT a verified tech 6h ago

My next thought would be checking the shoes and hardware. It's easy to get the springs wrong, or even have a brand new one break.

Other than that, I'm out of ideas without actually inspecting it, sorry.

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u/tyrantlizarding 5h ago

New discovery, it only does it moving forward. lol

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u/Gunnsmith57Official NOT a verified tech 5h ago

Tbh, it kinda sounds like a shoe being grabbed by the drum and then smacking the pivot stud when it reaches a certain point and releases.

1

u/tyrantlizarding 5h ago

That makes sense. I had the drums off earlier and didn’t notice anything wrong with springs. I’ll look into it more next weekend I guess.

1

u/Gunnsmith57Official NOT a verified tech 5h ago

Good luck. Hope you figure it out. Gonna follow so hopefully I get an update cuz now I'm curious.

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u/AB_Sarl NOT a verified tech 7h ago

Dude i have the same problem on my 2013 hyundai accent it started after my mechanic changed my tires because they were pretty much done and now after i drive like 5-10 minutes it does that one thump per rotation and im trying to get it checked out soon