I just bought a 2003 Civic Si. Two days after driving it off the lot I noticed a weird knocking sound while braking. Upon further investigation I noticed that when I brake lightly (while downshifting), the brakes make a knocking noise. However, when I brake hard with no downshift, they work fine and there is no knock at all.

I took the car to Midas. They told me there was some rusting on the rotors and drums, so they cleaned and adjusted the brakes for me.

Now the problem is even more pronounced, and I can hear the knocking even louder. I called the guy from Midas back and told him what was happening, and he said it's normal.

In my entire life, I have never ever heard brakes make a knocking noise while lightly braking, yet work fine while braking hard.

It is stressing me out because it feels like there are some loose parts or something, and I don't want to be on the hook for a huge repair...

Would a slightly warped rotor cause something like this to happen?

Is it a Canadian Si or an American Si??? I would say to check your lower control arm bushings... they could be the culprit of a knock. I have also heard tie rod ends could be the problem as well. The other thing could be that the calipers are seizing??? Any shake? other noises while braking? I don't see how warped or rusty rotors could cause a knock... They tend to cause vibration/shake or noise while braking, not a knock. Have you checked your pads?

Just to give you a few ideas. Good luck, sucks when you have a problem right after buying a car.

It is a Canadian Si with 150000km.

The noise is not that loud, and the radio needs to be off to hear it. It's not a complete knocking sound... it's kind of a mix between knocking and rubbing/grinding. And the noise is in sync with the wheels turning: As I slow down, the noise becomes more pronounced because it is rubbing slower on the rotor (at least that's what it sounds like).

Hmm... If it's a rubbing sound, like metal on metal. The civics have a heat shield for the rotors. If you take the wheel off you will see the shield plain as day. What I had happen to me once was the shield got bent somehow towards the rotor. Causing them to rub together, so every time I made a right hand turn it would make a whack of noise. To hear it I would have to have my window open and be turning right. Check it, if its really close that means it may rub when the wheel is turned. All you have to do is bend it back! Otherwise you should check your lower control arm bushings, tie rods, and maybe even tires. Those are the most common suspension problems, anyway.

Oh right and sometimes you can see on the rotor where the heat shield rubs it... it will wear some of the... rust off.

Good luck.

loooose lugnuts...

I hope not! lol

yeah i know what you mean about the grinding/rubbing sounds while turning. i think it happens with new pads before they get broken in. i had really crazy loud rubbing thats gotten better the more i use the brakes. i still get it tho esp while turning. i think its also the crappy brembo rotors i got now, im never trying anything else other than oem which was super quiet.

Have you removed the heat shield gearbox??? That caused a lot of noise for me because it bent inwards into the rotor. Just bending it out should stop the noise. Maybe when the rotors were changed someone hit the shield with a hammer and bent it in a bit and now its making noise.

I took my car back to the place I bought it, and they replaced the drums and fixed some steering linkages. Just picked it up yesterday, and it's still making the same noise while braking lightly. I'm beginning to seriously regret buying this car, considering I've missed 3 days of work already messing around with garages and crap trying to get it fixed.

Anyway, I'm going to look into the bent heat shield idea...

Also, does anyone think it could be a faulty brake caliper or caliper piston that is causing the knocking?

if its the caliper, i dont think the brakes would work properly. im gonna check the shields too. i noticed them a few days ago and they seemed okay, but i didnt actually inspect them enough to know for sure.

It's hard to actually tell if they rub... just pull the entire thing away from the rotor and see if it helps

can i just take it off? or is it too complicated/or the shield is useful.

Hmm, you can take it off... The heat shield is pretty useless really... But to take it off you have to actually either cut it, or remove the the hub. It's more involved than it's worth really. I think someone here put a DIY up at some point with pictures... I guess it's called a Dust Shield not a heat shield haha... teach me but I did find the DIY.

https://www.civicforums.com/forums/1...t-shields.html

yeah i tried to bend it, they seem pretty flimsy and useless. some parts werent bendable. i already get a ton of brake dust all over my car so i really dont see what theyre good for.

I finally diagnosed the problem with my car (it was making knocking sounds when lightly braking, but no knocking when braking normally).

My front passenger side wheel hub is slightly bent... when I brake my entire braking system is moving with the hub and causing the knocking. I'm assuming the guy who had the car before me must have hit a curb or something.

It took 4 guys at Midas 2 hours to figure this out... but at least they didn't charge me!

ouch that sucks, how much to fix it

hey benzeta i have this same exact problem! i just posted on it, i have the 03 si too....
idk what it is, brakes are fine, rotors are fine... i keep stressing about it because i don't want it to become a big problem.

i do not have this problem when braking lightly, i get the noise when slowing down from a higher speed.

shitty pads & rotors

Guys,
Same kind of problem with my 05 Civic Ex... any easy way to fix it
any wild guess how much it may cost?