# Rear Rotor Grinding Noise - Could it be the Parking Brake?



## MantisMan13 (Jun 27, 2004)

Saturday I swapped back my OEM rotors and pads I had taken off and replaced with a different set of OEM rotor and race pads for this past season's DEs at the Glen. That set work great with no unexpected noises and there we no problems with the original set that only had 3K on them before removal. 

So I reinstalled them as per instruction in the TIS, using ample brake lube on the backs or the pads and slide points.

Took the car for a prolonged drive Sunday morning to re-bed the pads. After about 100 miles or so I started noticing a scrapping or grinding noise but could not tell which wheel it was coming from or if from more than one. The noise would start when coming from a stop just after releasing pressure on the brakes and also when starting off it would make noise up till about 40MPH and then fade away. My first thought was that the calipers were too tight and maybe I need to remove a touch of break fluid so that the positions could retract easier. So I used a baster to lower the brake fluid a ¼ inch below the Max fill line. This made no difference. I had a friend walk around my car while I drove slowly and he indicated with certainty that the noise was coming from my left rear wheel. So I went to the store, got some of the GUNK spray and applied that to all rotors and took another drive around. No help there. But I did make a new observation. I decided to pull up on the hand brake to clean off any rust that might have built up while in storage and I noticed that I had to same grinding noise, and this without squeezing the brake calipers. So I play with the hand brake some more, and the harder I pull it, the louder to noise. 

Now, I believe my parking brake needs adjustment anyhow, as I don’t get wheel lock up unless I pull up so high and hard as to require flipping up the center arm rest first. 
And on this drive, with the road getting a bit wet with a fall drizzle, once I do lock up the rear wheels using the hand brake, the car will start to fish tail, kicking its ass out to the right angling to car toward the left. Locking up with the foot brake, and the car stops in a straight line, least so long as the road is level. This makes me believe that the left rear parking break shoe is activating harder and/or earlier than the one on the right.

So with all this, I am leaning towards this theory: The right rear parking break is making contact with the inside of the rotor hub, even when the hand break is fully disengaged and thus is the cause of the noise.

To resolve this, I should readjust the PB shoe at both hubs and then adjust the cable tension at the hand leaver.


I’ve read other posts suggesting to check for stones and bent dust covers, and of course, I will check for that too when I get under the car again, but Id love to know if what I’m think makes sense and is likely. I also have one other concern that I think is unlikely, but I guess worth a mention. When I when to push the left rear piston back in, I used a tool I got from sears that has a brace plate and a large tread plunger screw. With a pad over the piston, you torque the plunger with a ratchet to drive it back. Well, the piston was basically already all the way in and I torqued fairly hard with hand ratchet before I realized I was an idiot. So I’m concerned that I might have bent the caliper housing just a slight amount and perhaps that is causing the pad to not seat correctly and shudder about. Just seems like the forces which that caliper is built to deal with are like far greater than what I can create with that tool and a 10in ratchet. But then could I have damaged the piston itself in driving it in to hard. But all in all, I’m leaning toward not having hurt a thing and this being all due to the parking break.

Also, I’m not sure exactly how the parking brake adjustment is made at the wheel. The TIS says to rotate the wheel with one of the lugs removed until you see the adjustment screw and to use a screwdriver. Not much more. I don’t recall seeing any sort of screwable adjustment back in there one time I had looked for it. I only recall seeing the sprocket looking thing in between the springs that looks like you could rotate it on way or the other, but not likely without removing the wheel. Can anyone with experience adjusting the handbrake on late model E46’s give me the skinny on how this works. It may be I just need to get my eyes checked and look again, but some foreknowledge of what to look for would be grand.


I thank you all for any help and comments you can offer here.


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## MicahO (Apr 19, 2004)

You've got a pebble or some grit inside the P-Brake hat on the rotor. This happened to me about 2 months ago. here's how you fix it:

1) Panic! You really don't want to have brake problems on your car.

2) Call your local Stealership and make an appointment. My car is still under warranty, so I can do this with no fear of incurring costs, but you should take this step even if your car is out of warranty. Hopefully the appointment is a week or 8 days away.

3) Stop Panicking! Now you've got an appointment and the pros can figure out what the problem is. In the meantime, your brakes seem to be working fine, and nothing seems to be falling off the car.

4) Drive the car as you normally would for a few days. Within 5 days, the grit/pebble/whatever is in there will grind itself to dust and the noise will go away.

5) Wait a day or two to be sure, then cancel your appointment.


Seriously - it's probably goign to be something that grinds out. I spent a lot of time thinking about the noise - I even had a horrendous crunch one time when I put on the P-Brake, and after that the noises were even worse. But in a couple of days (and actually after driving home in a tremendous gully-washer) the noise was gone. As long as your road brakes are working properly, it's highly unlikely that what you describe is anything other than some grit in the P-Brake.


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## MicahO (Apr 19, 2004)

A followup question - only somewhat related - 

You had a few days up at the Glen, I'd like to pick your brain about your brakes--

I ran a school up at Lime Rock 2 weeks ago. It was my first real track experience, and I stayed with the stock rotors and pads. They held up well, never experienced any actual fade during any of the lapping.

HOWEVER - the beginning of the 3rd and 4th run groups, the pedal started out a bit soft, or more precisely, the pedal engagement seemed a bit low. Braking was fine, but I was pushing further into the pedal than I expected. As I got some heat into the brakes, the pedal returned to the height I have come to expect from the car and stayed there for the entire session. As I mentioned, there was never any heat related fade during the sessions - the brakes were really great for that particular track.

Since that track day, the pedal has remained a bit low. If I touch the brakes, then get right back on them, the pedal is up where it should be, but that first touch at the pedal seems to be 3/8-1/2 inch lower than I'd expect. I had bled the brakes the weekend before the event, new ATE blue with a pressure bleeder, and I bled them again the Friday after to see if the pedal would return to the expected height. (I also bled the clutch out afterwards when I swapped in the modified CDV). 

The re-bleed made no change in the slightly lower pedal height. The pedal drop happens even when I'm sitting still (on the brakes, off the brakes, wait 10 or so seconds, back on the pedal) so it doesn't seem like out of round rotors are pushing the calipers further open than they should be.

Any thoughts from someone with more track time than I? I keep thinking about the physics of the system - if the fluid is good, lines are good, rotors are good, what about a warped pad or backing plate forcing a caliper open when it's cold? I'm tempted to get some line clamps and go one corner at a time, testing to see which corner is giving the extra movement.

Thanks---


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## MantisMan13 (Jun 27, 2004)

Hi MicahO

Mystery pebble, eh. Well you never know. I’m waiting for a nice day to get out and adjust the parking breaks and I’ll find out then. I could do the Panic! Then jerk the dealer’s chain bit, as the car is bran spanking new, but since I’ve been playing with the set up my self, why beg the confrontation. Pain in the ass to waist a day that way anyhow. As I work from home and only realy use the car on the weekends or for out of twon biz, it seems driving it out isn’t my answer either. I had a noise like this to a slightly lesser degree when I put on the other set of rotors, and it almost faded away by the time I changed them. I thought the grinding was the pads braking in. However, I did rotate that parking brake sprocket one click when I did the brakes the first time, not really knowing what the hell it was. So I think it’s likely I raises it up a tad. So with ware, the shoe rubbing on the hat may have quite down and worn the inside of the hat a bit much. So now with an unworn slightly corroded hat to work against, the noise is back in full force. But still, might be a pebble, or the dust shield. I was resting the calipers on the shield a bit, might have bent it down a tad, but I doubt that too.


Ok, so with 4-track day under my belt, I’m an expert on brakes, Right  ? Not sure what you got there. As I was reading, I was thinking boil off and you just need to bleed, but you thought of that first. So my only thought is that you may have un-even pad ware. Did you make your runs with DSC enabled or disabled? If you were pushing the car hard with DCS on, then it may have been working the brakes a bit more and I've read people talking about ABS action causing uneven pad ware in that the inside pad will ware faster than the outside one which is easier to inspect. So if you’re outside pad is thicker than your inside, it might take a bit more pursuer to extend to inside piston to point where it all grabs down, especial when the system is cool, and who know how things change as it all gets hot, but shoudl keep the pads up against the rotor I would think. But I would check my pads and see if they are waring evenly or not.

Other thought is since they were just the OEM's and not track pads, you may have over heated the rubber lines that feed the pistons. Check for distortion and bubbling in the lines. I've never seen this and I'm just guessing what might happen if they over heated but didn't burst. But say the diameter of the hose changed slightly. This might change flow rate and thus peddle feel. Seems like they would have fadded on you if it got so hot as to do any of that. Ah, check the pad first.


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## MicahO (Apr 19, 2004)

MantisMan13 said:


> Hi MicahO
> 
> Did you make your runs with DSC enabled or disabled? If you were pushing the car hard with DCS on, then it may have been working the brakes a bit more and I've read people talking about ABS action causing uneven pad ware in that the inside pad will ware faster than the outside one which is easier to inspect.


Interesting to hear about the DSC experiences. I did run with the traction control in full-nanny mode. As my first school, I was letting the DSC keep the throttle tame while I used my brain for watching lines and braking. Particularly on the uphill - this is what happened to the NJ chapter's Instructor Emeritus on the very first lap of the day - cold tire, cold track, over the uphill he got loose - kind of turns one's stomach, I was happy to leave the DSC on.

In full DSC mode, there is a lot of throttle cut-out, and then braking activity when cutting the throttle was not enough. After one click, the throttle is left alone, but the brakes start getting hit when you are near the limit. Either way, it's very likely that I was getting a lot of braking input from the rear end without really expecting it. Most of the second, third and fourth sessions I saw the DSC light flashing for everything but the straights.

I'll give a couple of weeks to let things scruff down. If the behavior is still going on when I'm putting on the snows, I'll try scuffing the pads by hand, or perhaps replace the rear pads entirely.

Thanks much for the input!

I hope the noise in the rear works out - just pulling the rotor and hitting things with a brush should be all it takes to sweep away the noise. The offending noisemaker will probably be visible, and you'll wonder how something so small got in there and made so much noise.


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## guzplace (Apr 16, 2004)

brakes getting mushy after hard use track days .... 

help us guys
i also suffereed from this .. what's the story ?
what are the causes ?


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## MantisMan13 (Jun 27, 2004)

guzplace said:


> brakes getting mushy after hard use track days ....
> 
> help us guys
> i also suffereed from this .. what's the story ?
> what are the causes ?


Check Pads, Bleed, Maybe even a full flush, rotor thickness, line hoses. All of these things play a part in how well your car brakes and what the pedal will feel like. If you haven't flushed your brake fluid, there is a good candidate for the culprit. Heating up you brakes on the track will stand a good chance of boiling off any water content in your fluid and possibly even the fluid it self. I don't know how well vented the 318i's are, but if it's like the 330's, there is very good air flow to the fronts so over heating isn't as bad as it could be. The big clue that you've toasted your brake fluid is if they ever noticeably faded on you. If you don't know what if means to have your brake fade or your unsure whether it's happen to you, then you haven't had it happen. The car I learned to drive on was a 76 Volvo 244DL and a tank by all account. This car thought me many lessons on brake fade at young age. These bimmers have to be pushed a bit harder than that Volvo before they get hot and soft and eventually non-existent, but if you ever get there, believe me, you'll know it. You can literally put your foot to the floor and have little to no braking action. Your parking brake and a quick down shift are about your only hope at that point.

So, did your brakes fade ever? If they did: flush your fluid. The other thing about heating up your fluid is that it tends to let any trapped O2 let off from boiling water content form into actual air bubbles and get trapped inside the piston or other parts of your system, and this will make your pedal feel spongy.

Good Luck


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## guzplace (Apr 16, 2004)

what about overheated brake pads ( old pads ) not new pads ... that become glazed

what are the chances of glazing stock pads on the track ( well bedded in ... let's say have more than 2,000 miles on them )

you did not mention glazing as one of the common causes of brake feel and performance to become different


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## MantisMan13 (Jun 27, 2004)

guzplace said:


> what about overheated brake pads ( old pads ) not new pads ... that become glazed
> 
> what are the chances of glazing stock pads on the track ( well bedded in ... let's say have more than 2,000 miles on them )
> 
> you did not mention glazing as one of the common causes of brake feel and performance to become different


Didn't know this was a test,  but I believe my first comment was to check your pads. Glazing isn't however anything I've ever experienced or know much about from any other source so I can't speak to much to it. I've always heard that the glazing from proper bedding in will help brake performance, not hurt it. But maybe that dosn't hold true with all pads, so I don't know. I think if your petal feel is soft and it's always soft, bleed your system first. Certainly can't hurt.


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## MantisMan13 (Jun 27, 2004)

*And the winner is.....*

Dust Cover..... was rubbing ever so slightly. Pushing it back with a flat of a screwdriver along the perimeter did the trick.

However, I still needed to adjust the parking break and found it almost impossible to get that sprocket to move when the rotor hat is in place. Spinning it clockwise ( up and to the right ) is required to tighten the shoes to the hat before backing off a click or 2 and what should be done on both side to ensure equal gapping before adjusting the cables. I did slacken the cables before attempting any adjustment to the shoe height. I was using a simple flat headed screwdriver, but found that once the rotor hat was in place, I simply just did not have enough leverage to move the sprocket one way or another. I was able to get my parking break adjusted via the cables, however they are not tensioned evenly and I'm sure that is due to not have an equal starting gap.

Does anyone know a trick or a better tool for making the adjustment to the parking brake gap when to rotor and the tire for that mater are inplace?


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