I have a 2010 LS, manual, 1 year old, 7500 miles. Lately when I use the brakes when slowing down, there's an ominous noise. It's a "thump-thump-thump", with the frequency of thumps decreasing as the car slows. It's possible there's one thump per revolution of the wheels. I can hear it when going under 20 MPH. It only happens when I have my foot on the brake. It happens the same when the car is in gear or if it's in neutral. I haven't noticed the noise when braking in reverse, only when going forward. The thumps seem to occur in the front.

Any idea about the cause or what to check visually? The car is under warranty and I'll probably take it to the dealer, but I thought some here might have experienced a similar issue or know what it might be. Thanks in advance.

 

It sounds like you have a case of brake judder, more commonly known as warped rotors, but usually in the case of the HHR a deposition of brake pad material on the rotor itself resulting in a judder as you stop. The thumping you hear is the caliper/calipers moving about as the pads alternately grab and release the rotor.

HHR's are known for this issue due to the rotors being a bit on the thin side even when new, and a less than perfect choice of friction material on the pads from the factory. One thing the dealer should also check before attempting to turn the rotors, is for a buildup of rust between the rotor and hub mating surfaces since this can also cause the juddering.

If the dealer turns the rotors that's it for them, there just isn't enough meat to turn them more than once before reaching their service limits, so you may want to see if the dealer is willing to upgrade the pads and rotors under warranty to something better than OEM quality.

 

All they will need to do is a light cut to clean them up. It will not remove enough material to really hurt much unless they are scored.

While the factory pads could be better you can prevent this from happening again if you properly seat the pads in when you get it back. Very few owners and very few mechanics will seat in pads when new. This lays a even coating of pad material from building up in one place to cause the judder often mistaken for a warp.

If you take the car out and do several hard stops from 45-55 MPH. [check the brake MFG web sights for their instructions on how to do this. All vary a little on how best to do it] THis will help prevent the judder from happening. I had this issue on many different cars and used to never seat my brakes in. Since I started to do this I have never had the issue since. I also have started to use higher quality pads as they work a little better for heat disapation and often less dust.

Note often the material will stick to a unseated rotor after a hard stop like a off ramp and then sit with the pad press on the hot rotor at the light at the end of the ramp. Some times it will go away but often it will not.

This is not just an HHR issue but a insdustry wide issue. The newer pads seem to be more apt to do this and often the rotors and other things get the blame. People replace things like rotors with drilled and slotted rotors and still get the same issue as it is not the rotors fault.

The other issue that can happen is Rotor Thickness Variation. This happens when the bearing gets .002 out or more and lets the rotor wobble. This in turn will wear the rotor thickness uneven and create a pulse in the rotor as it compresses the piston in the rotor in and out. They have to cut the rotor to clean this up too.

Note if you do brakes in the future just replace them with a good stock rotors like Bendix. THey will last as good as anything out there and they are affordable to replace at brake change time. I don't even cut rotors anymore since they are cheap and brakes last longer anymore.

I think 843e has it right on the judder and it is easy to fix and if you seat them in odds are you will not have the issue again.

 

Mine started doing that at 25k..at 30k I changed pads and rotors and it went away,,smoothed out the ride too,,,rotors had a good amount worn away and one inside pad was cracking, left side was against squealer bar..didnt trust them for a cut, figured they would warp.

 

It might be the brakes as previously mentioned - but that typically would also be felt as a vibration through the car as well as through the steering wheel. Do you get that as well?

If not, you may have a tire that is having a problem - belt separation, impact damage, delamination etc..

Best to get it checked at the dealer being it is under warranty.

Keep us posted on the results :)

 

Thank you very much for all the responses (so far and any future ones). I'll schedule an appointment to take the car to the dealer with those points in mind.

In addition to hearing the thunks when braking, I believe I can feel them a bit as well.

My brake usage is as gentle as can be. Only had to do brake work once with my previous vehicle which lasted 15 years.

 

I'd ask the dealer to make sure the adjustment of the rear brake shoes is set right, also..

Yes the fronts do the majority of stopping, but the rears need to help. Or the fronts work too hard..

my .02

 

X2 ^^^ This makes a huge difference ^^^^

 

X 3, forgot about the rear adjusters on such a new unit, but they should be checked and adjusted if they need it.

 

Larry Pelican,

I agree with sleeper and Greyberad999. I look forward to ready any updates that you would like to provide to us.

I hope that you are having a great day!

Michelle, Chevrolet Customer Service