Trying to diagnose wheel speed related “swish, swish, swish” sound.
“Ah!”, I think. Sounds like a brake pad binding, on a rotor that’s not quite true. Off I go to remove the wheel, and sure enough, when I turn the rotor, it turns freely for about 3/4 rotation, and binds on the remaining 1/4.
So, remove, clean, grease pads and calipers. Done. Except that when I turn the rotor with the caliper off, it still has the same binding as when it was on. Strange. And when I reassemble everything and go for a drive, I get the same noise.
Is it an issue that the rotor is harder to turn at some points than others? Or is that a red herring?
Didn’t want to over complicate the problem with this information before, but I replaced strut / spring and a ball joint on that wheel, after the original spring snapped, and the problem appeared after re-assembly.
Next most likely place for problem is wheel bearing or half axle. But I don’t know how to diagnose.
I don’t have typical symptoms of click or pop for CV joint, or grinding noises for wheel bearing and I’m a bit stumped about that.
I assume you checked for play in the wheel by trying to rock the tire back and forth holding tire at top and bottom for wheel bearing check. Next with drive wheels secured off the ground and traction control turned off, have the wheels turning at no more than 30 MPH and use a stethoscope at hub . Don’t do this if your not familiar with the safety precautions for this test.
When you reinstalled the brake rotor after doing those repairs, and there was corrosion on the hub flange and rotor, and the rotor wasn’t re installed back in it’s original orientation, the rotor may now have excessive run-out.
That’s why they make this tool to remove any corrosion from the hub flange and the backside of the rotor so that doesn’t happen when the rotor is reinstalled.
Not all wheel bearings make a grinding or rumbling noise when they go bad. You mention turning the rotor with the calipers off. Does that also mean without brake pads and possibly the caliper yoke?
I’m also assuming that “grease pads” does not mean that literally. Axle seated fully?
I didn’t remove the rotor from the knuckle. The shop manual said to remove the knuckle and rotor assembly from the shock as one unit, and then remove the knuckle from the strut.
There is some fudge factor on how the knuckle and strut go back together, (they alignvia a tab on the strut) but I had an alignment done after the repair, and according to the computer print out, it’s fine.
I’m turning the rotors by hand, with the calipers and brake pads off. Caliper yoke was still on, but I can see plenty of clearance there.
Grease pads - I meant grease the contact areas on the back of the pad. Maybe if I grease the front the noise will go away though
Axle better be seated fully. VW seems to have an obsession with bolts instead of nuts. They use a torque to yield axle bolt - 140 ft/lbs + 180 degree turn afterwards. I need a I need a 4’ section of lally post on a 2’ breaker bar to get that last 90 degrees And every time I pull the axle for something I need a new $10 bolt. What the fsck is wrong with castle nuts?!
Sorry about the multiple replies. Just learned about @ syntax.
Thank you all for your helpful replies, more advice is welcome, based on what I answered.
For now, I think I’m leaning towards the wheel bearing, based on the fact that the rotor doesn’t spin consistently, even with the calipers off. But If it is the wheel bearing, it would be frustrating because it means that I broke it, in my boneheaded attempt to get the axle bolt out.
Thinking it was just seized, I used a propane torch and an impact to remove it. Now I know you need a 6’ pry bar and a 300 lbs buddy.
Here’s some new data points for your diagnostic magicianship.
Before doing any real work this morning, I took it out for another test drive, and I discovered that:
a) The noise gets louder when I apply the brakes
b) It gets quieter the faster I go. Above 30 I can barely hear it (of course, it could just be road noise blocking it out, I suppose).
Ok. Stupid me. The fact that I had recently redone the struts at the front, and the noise started after that was a red herring. It’s almost certainly the rear left brake. The pads are rubbing on the rotors. I can hear it touching intermittently as I spin the wheel by hand. And I can see the rotor is only wearing in two 1/2" stripes.
I changed over to summer wheels when I did the struts, and I’m guessing I maybe over torqued the lug bolts and warped the rotor, because I had to use a sledge on the tire to get the wheel off.
What to do now? Turn the radio up and hope the pads and rotors re-bed themselves? Get the rotor off and get it turned (there’s only about 15K on it)? New pads and rotors?
