1998 C70 Coupe "thunk thunk thunk" and brakes

57wayne · Post by **57wayne** » 28 Aug 2013, 08:07

On my 98 C70 coupe, I have a noise that shows up going downhill when you let off the gas, and can trigger also if I turn to the left. As in the description above, it is a 'thunk thunk thunk' that varies with speed. Guessing inner CV joint on the left.
I have new Zimmerman 302mm rotors and new pads on the front, and good rear rotors (not that old, but not new) and new Wagner pads on the rear. Bearings seem to be OK all around. Replaced one, I think right front, a year ago. When I apply the brakes, as in a normal slow-down, the car feels like there is something loose or wrong with the brakes, almost like a major fade, not a good firm stop. If I press hard, they pull down fine. The front pads are wearing fine, and everything is tight. Just changed the rears last night, and they too were fine and really had plenty of wear left.
When this started, I assumed the slotted rotors up front had worn enough to have 'messy' edges and were catching the pads. They have also been changed out in the rear.
Thoughts?

Post by **jblackburn** » 28 Aug 2013, 09:23

That sounds an awful lot like your wheel bearing to me. The bearings are a sealed unit and may *appear* to be OK visually, but are loose inside. They'll do exactly that - a "whap, whap whap" noise at speed without an acceleration load, or when turning a certain way. Turning left would be loading up the right bearing and unloading the left, so that would make it the left one making the noise.

Bled the brake lines or changed the fluid recently?

57wayne · Post by **57wayne** » 28 Aug 2013, 09:35

I had a bearing do the whining/whirring sound that I would expect. I haven't heard a bearing do the whap whap whap but if you have, that could be something I am missing.
I have not bled the brakes recently (maybe 2 years). Fluid had been changed by serendipity...swapped calipers a couple of years ago and so all the fluid ended up new by the end of the swap and bleed.

57wayne · Post by **57wayne** » 04 Nov 2013, 14:04

Update: I swapped in a driver side axle and hub from my parts car. Inner CV joint had sprayed grease onto the subframe and transmission so probably had none inside. Now have no noise, and no problem with the brakes.
Case closed. Thanks!