View Full Version : Loud howling when turning left

03-22-2016, 09:48 PM
This started after I installed a front disc brake kit.

I was busy so had my buddy Joe at Classic Metal in Mocksville do the conversion. Joe has 40 years experience and is a professional mechanic.

Symptoms are, when I turn left only, a low frequency howl. It's not a tire rubbing. It happens at any speed. Joe tried to diagnose it while I drove. He discovered that when I apply the brake the noise goes away. The noise is from the right side. Joe (passenger seat) and I (driver) think its from the right front wheel. When Mike rode in back he thought it was from the right rear.

There is no tell-tale contact areas from tires making contact. It doesn't sound like rubber on steel anyway.

Joe and I took the left front wheel off and checked the brakes. The pads were new and were not making complete contact with the rotor. The bracket (part of the kit) was very close to the ID of the rotor so Joe ground down a small area for additional clearance. This had no effect.

I've driven the car a bit to fully break in the pads. I removed pads (both pads, both right and left sides of the car) and applied a generous coat of squeal stop, and followed the directions to the letter. During disassembly of the right side I did find a lot of slack between the inboard pad and the rotor. No effect on the noise.

Both front springs are new, installed along with the brake modification. I inspected those; all rubber seats are in place.

I cleaned and adjusted the rear brakes. The E-brake works better now. No effect on the noise.

I replaced the rubbers on both front shocks, as I had a rattle on the right side. No effect.

Any thoughts?

03-23-2016, 07:53 AM
Did kit replace spindles? (thinking maybe alignment, but that would be tire scrub/screech noises). Do brake pads have "anti-squeal" spray, goop, or small pads between them and calipers?

03-23-2016, 07:56 AM
Are you using backing/air deflector plates behind the rotors?

Robin says you may be hearing from a great number of wolf spirits in your area that may have died at the hands of murderous Thunderbird drivers. A shaman can save you, Steve. - Dave

03-23-2016, 09:06 AM
Shaman on you Dave!

The spindles are original. Alignment done after the conversion. No backing plates. I applied a generous amount of CRC Disc Brake Quiet applied to the pad backing plates before my last test drive- no effect.

03-23-2016, 12:03 PM
If all that is true, something is flexing. I put my money on loose spindle nuts IF your bearings are good. Pull the wheel off and check it. - Dave

03-23-2016, 02:44 PM
I checked the bearing pre-load with Joe when checked the assembly clearances the first time. I fact I remember quizzing Joe on his method of applying pre-load, to see if was how I book-learned how to do it 30 years ago.

03-23-2016, 04:24 PM
Howling is usually a bearing

03-24-2016, 08:10 AM
I had a similar situation. It turned out to be my sway bar would rub against the vibration damper when turning left. The left front spring was sagging slightly. The short term fix was to space the sway bar bushings down about a half inch. I'm sure this will correct itself when the springs are charged.

03-24-2016, 10:12 AM
Well, both my sway bar, links and bushings are new, springs are new. I'll check this today or tommorow when I visit the shop.

The wheel bearings are also new, part of the disc brake kit.

Everything so far is pointing to the excessive play in the new caliper that I found during disassembly. The piston self-retracts, leaving a significant play between the inboard pad and the rotor.

Last night I took my bride on a short drive and she cut it short because of the noise. :(

03-24-2016, 04:23 PM
How sharp a turn are you making when the noise occurs?
It might give us all a clue!

03-24-2016, 05:18 PM
It would start with the steering wheel about 90 degrees left of center.

03-24-2016, 06:46 PM
How sharp a turn are you making when the noise occurs?
It might give us all a clue!

It will happen on a curve in the road as well as a sharp turn, regardless of speed, no difference in volume or frequency.

bird 60
03-24-2016, 07:48 PM
Just for the fun of it, even though it would be more of a growl, check the power steering fluid to see if it's low. Mainly because of you making a turn it would do it.

Chris......From OZ.

03-25-2016, 03:48 PM
The fluid was about 1/4" low, so I filled it: no change.

Here's a video of the noise, maybe this will help in diagnosis.


03-25-2016, 03:56 PM
I took both front wheels off and inspected the brakes on both sides, using the left side as "normal". Based on the wear on the rotor, the right side inboard pad is definitely not making as much contact at the outboard pad. Here's a video of my inspection of the front caliper and rotor.


I then took the caliper off and "reset" it, then drove the car, and the noise had gone away until the first time I applied the brakes. Then the noise reappeared at every left turn as before.

03-25-2016, 07:16 PM
From looking at your vid's, I say your brake pads are straightening your rotors. That means your hub is loose.

I thought you would show the caliper hardware but the camera was too low. What calipers did you buy? Were they 'loaded'? Do they have all the rubbers?

Without being there to personally inspect your setup, it's nearly impossible to properly diagnose from this chair in Michigan but that's my opinion. That drone is nasty and excessive. Start at the hub, then go to the caliper hardware and finally the pads. Did you properly bend the tabs over on your pads before installing them? (See, I have more questions than answers because I only know what you tell me.) Your calipers have one piston and they should equalize easily. - Dave

03-26-2016, 01:46 PM
I've been thinking of your problem and was looking for pictures of your setup but I guess you don't have any because you weren't there during the installation.

Are you sure the donut is in place and properly oriented on your spindle?

03-26-2016, 02:05 PM
The hub isnt loose since there is no play when i move the tire in-out. The outboard pad is tight against the rotor, the inboard is loose.

What is a donut?

I have an email out to the supplier to obtain the make and model of the calipers. I think they are a GM style. I'm thinking of rebuilding it or replacing.

I was not aware that the clips needed to have tabs bent to install, ive always slid them in place. Both sides are installed the same way.

03-29-2016, 10:16 AM
The calipers are GM D145. Browsing Summit Racing, lots of pricy options, including Wildwood. The vendor emailed me back, saying that are OE on a '94 Chevy S10 2WD. O's had a right side in stock for $18.

It looked the same as the old one, just a different manufacturer. I had some silver high temperature paint on my shelf to match the old one so brake-cleaned it then painted it.

Then I found that didn't bolt on. An inspection of the old one revealed that the vendor had ground off some of the tabs to fit his custom bracket. I had to do that and a little more. And to think that I was thinking of selling my big ol' Craftsman portable grinder...

03-29-2016, 12:13 PM
That's wonderful information but I thought we already established that your calipers are an S10 setup. BTW, the 4WD version works just as well and they are interchangeable. I'm using the 4WD version on our Galaxie.

Experienced S10 brake mechanics bend the tabs on the outer pads to eliminate any slop. Inner and outer pads do not mount the same as the outer pads 'hook' onto the caliper.

The 'donut' is a metal spacer that your hub seal rides on. It is the only new part that fits around your spindle. If you have someone else install the setup, you miss much of the details.

So, why a spacer/donut? I'll let you figure that out.

Did the new caliper fix the howling problem? I'll stick my neck out and say, you probably still have the howling because you said your old caliper was releasing. If all the caliper hardware was there it should have equalized easily but you never answered the question about the rubbers or if you bought the calipers loaded. - Dave

03-29-2016, 12:31 PM
I must have missed where we established that the calipers are from an S10. Or maybe my memory failed me yet again. I have a word document that I'm slowly adding to for the next owner of this car to help out and explain these modifications. Under this modification I wrote the model number for the caliper but not what vehicle it was made for. Now it has both.

I didn't see any reason to bend the tabs on the outer pad clips. The clips hold the pad in place so I can slide the caliper on and that works for me.

What you call a donut I guess I would call a washer. Or maybe you are referring to the adapter that increases the OD of the spindle to fit the ID of the new inboard bearing?

Regardless, problem resolved. I just test drove to O's to return the caliper core. No howling, no noise, no brake issues whatsoever. :)

Now onto the next issue.