'05 G35x

Replaced the rear pads and rotors two weeks ago, but just now noticing (after about 50 city miles) that one of the two rear systems (driver side) seriously heats up, begins to smell and even smokes after a short drive. Both sides seemed fine up until a couple days ago. The passenger side is not exhibiting any of these symptoms to this point.

Furthermore, the driver side rotor has begun to turn a bluish-gray color whereas the passenger side is still silvery-white. Both are beginning to rust just slightly (rust is normal, obviously). The driver side rotor is beginning to show slight ridges ALREADY. The passenger-side rotor is still smooth and flush across the entire surface. I haven't noticed any unusual sounds (scraping or rubbing) so it doesn't appear, at least in that respect, that the pads are in constant contact with the rotor.

Prior to installing the new rotors, they were cleaned with brake system cleaner, so that shouldn't be the issue. (The pads were not cleaned.)

I used the 30/30/30 burnishing method (braking from 30 mph, 30 times, with a 30 second cooling period between stops).

From what I've read online so far today, glazing could be the issue; although, I'm not fully certain what glazing is (everyone seems to have a different opinion on that one), the piston and/or caliper could be seizing up (not cleaned or lubed properly), I didn't clean the new rotor surface well enough (shouldn't be the problem because I'm a neurotic clean freak and they were probably over-cleaned) or that this is totally normal for new brakes, though I've never experienced this in the past and there's no way the rotor should be this freakin' hot (also, these symtoms only appear on the one side).

The front pads are wearing down somewhat close to needing replacement. They were at 25% about a month ago, so this shouldn't be a case of the rears having to do all the stopping for the car. (I'm noticing a slight buffeting sound, a rhythmic *phfft* *phfft* *phfft*, from the front passenger wheel that speeds up and slows down with the speed of the car. Is this possibly the warning system that tells me I need to replace the front pads? I've only had brakes that squealed when they need replacement.)

Thoughts and proposed solutions are greatly appreciated!

 

If your rotor is turning blue, it's definitely overheating. You need that caliper looked at. You very well could have a seized caliper. Not sure where you got the 30/30/30 method for bedding your pads in. That's excessive. Most new pads come with burnishing methods preferred for that brand of pad. I have Hawk pads and it was written on the box. It was 4 or 6 times at 40 mph and 3 or 4 times at 60 iirc and then just drive around without using the brakes for several minutes to let everything cool down.

Something is definitely not right. Get it looked at soon before something breaks.

 

Check if caliper sliders are free-those pins on which floating part of caliper is mounted. Your break in procedure does seem to be excessive-especially for stock sized pad. Heat may have cooked the grease.
I had mine stuck to the point of me having to hammer it out. It killed a pad and scored the rotor. After cleaning and proper brake high temp grease it was ok-for 2 years now.

It is very easy and cheap fix. If it won't help, then culprit is a caliper piston. Can't help you with that.

 

Ditto. Pull off wheel and check the brakes by trying to move the caliper along it's usual "sliding" axis. It it won't slide, disassemble and before lubing try to compress the piston into the caliper. If it is very difficult to push back in you have a bad caliper. If it compresses easily into the caliper body then clean all the slides well and use alot of lube and reassy.

If you are worried about replacing the caliper, it's very easy, just make sure you bleed the system when you are done. PM if you have questions, I've done this very thing to my car and can help you out.

You should probably invest in a new driver rear rotor and pads. That heat can damage the pads for sure. I replace my rotor and pads when it happened to me for peace of mind.

 

Unfortunately, it's been raining all day today, so I won't have a chance to take the wheel off until tomorrow. If I have any additional questions, I will post them at that time. If I'm able to determine the cause, I will post that information as well. Thanks for the advice.

(The burnishing method used was recommended by the rotor manufacturer. Only completed about 50% of the entire process though, as I also thought it was excessive.)

 

By the way, what does a bad or "burnt" pad look like? How will I know if the excessive heat has already damaged the new pad?

 

bluish-gray color on your rotor is over major over heating as previously stated by other members. Just for safety sake replace it. Seen to many rotors shatter because of over heating.

As far as your pads, burt/carmelized pads look like a brownisk black and smooth (almost feels like glass) also if they are cracked. If you remember what your pads looked like when you put them on and if they are a lot darker and have a burt smell replace those as well.

 

Well, still haven't been able to diagnose the problem. Tried to take the lower slide pin out and ended up with a stripped head. Wasn't able to get the caliper off the rotor to investigate further. Headed off to Sears to buy a kit to get the bolt off. The other slide pin (as well as both on the passenger side) were well greased and moved easily, though.

Anyone know of a web vendor that sells the correct size slide pin? O'Reilly's doesn't carry it.

 

Check autozone or naps or I hate to say it but try the stealership if all else fails. You wont strip bolts if you use the correct size socket and make sure its a six point socket. Never use 12 point sockets when working on a car.

 

NO! You do not need to take bottom bolt out. Just the top and the caliper to knuckle bolts. Bottom one is just a sliding pin. I think it is mounted there permanently. Don't worry about stripped head-you will never need to take it out.

First of all-remove top bolt out-then pull caliper top part forward. There will be resistance, because pads are grabbing rotor. Just yank it. It should rotate around bottom bolt and when out, slide away from you. Suspension arm will not allow you to take it out completely. Then undo 2 caliper bolts.

 

I think you mean the torque member, right? The thing the caliper mounts to?

I stripped my lower pin, too. I quickly realized you can slide it off... even the FSM states to only remove the top pin. Lesson learned for all.

 

i just replaced my stock springs w/ z springs. & i also painted my calipers while i was at it, for the 2nd time. and whenever i'm braking i smell a burned rubber type of smell. im hoping that it's just paint burning off, if not i'll have to get it checked out

 

There is one thing you might check that often gets over looked is The Rear brake rotors have the parking brake shoes internally. If you cleaned
the outside rotor surfaces and not the inside, and there is any residual grease or contaminates or if the brake shoes are dragging this could cause friction on the hub and result
in heat build-up, If you have a infer-red temp gun shoot the rotor right after driving the car, I mean within a minute or two.start at the hub and go out to the edge. The heat will be concentrated on the rotor hub if it is a parking break failure issue.
Just a thought.

 

Good call. Forgot all about that.

 

Here's the latest update on my attempts to solve the problem, although I don't have a definitive way of knowing what exactly has the cause:

Decided to replace the entire caliper (only on the problem side... driver side). Upon insepction of the old caliper, I found it was quite difficult to push the piston back in, so that could have been the problem. Bled the system and took a mile long test drive. Even after a mile the rotor heated up just as much and there was the same amount of smoke and burning smell. (Imagine my dismay at this point.)

Decided to try bleeding the system again in case there was some air left disallowing the calipers to re-open all the way. Well, that fixed about 75% of the problem. On the second test drive I could actually hear intermittent rubbing, which meant less contact and quite possibly an uneven rotor surface. Furthermore, the heat was considerably less, as well as no smoke and only a light burning smell. After speaking with a few individuals who know about cars, we ultimately decided it could be one of two other things (if not both): Either the rotor was too big (defective) from the get-go or there was a crimp in the fluid hose to the caliper. Took it to a mechanic yesterday. He didn't find any issue with the hoses, though he did recommend replacing them. Instead he found the rotor to be warped from the excessive heat and grinding. He turned the rotor, re-installed it and said that fixed the rubbing issue. (He also recommended replacing the other rear caliper since it is commonplace to replace both if you're going to replace one.)

After I plunked down the money and took her for a 10-mile drive in the city, the rotor heated up again, just about as hot as it did at the very start of this whole mess. It smoked and smelled pretty badly. (I'm sure by now you're imagining me shouting obscenities as you read this sad and frustrating story.) Called the mechanic this morning and told him I was having the same problem again. He said I should change the other caliper because the new one could be working much better than the old one and thus overcompensating for the caliper on the other side. My initial reaction was: Well, if the other side with the old caliper is also heating up, but to a degree that is normal (as opposed to being cold), it would seem that it's working as it should be.

Does it sound like the mechanic could be right? Is my new caliper working over time because it's in better condition than the old one? Before I purchase another caliper for the other side, does anyone think I should remove the pads from the new caliper (the problem side) and scrape them off on some concrete to see if that makes a difference? If the pad surface is burnt on the driver side, then would running them on a newly turned rotor cause this excessive heat and smell? I would think smell, maybe. Heat, probably not.

I've about had it with this problem, so if anyone has any additional insight that might lead me to an ultimate solution, I would be forever grateful! (Oh, and thanks for the hint about only removing one of the caliper bolts... Mine was only slightly stripped, so I had someone else try and remove it and he was successful.)