Hi all,

I've been searching the forums for advice on tackling this job on my wife's car. I've read about the sensor light replacement which came on about a week ago on my wife's car. When the sensor light comes on, should the brakes and/or brake pads be replacement immediately, or do they give you some time? I haven't really looked at them yet, but will probably do so tonight.

Also, I did read about how sometimes the rotors need to be replaced at the same time as the pads, can anyone give me a visual clue that I will need to look for on the rotors to see how bad they are? Do the brakes have the metal tab that gets closer and closer to the rotor and starts to squeek like on my domestic car?

Also, I am little confused about what body style her car is. I think it changed in 2000 right? So does she have a E36 or an E46?

I'm off to look for some website with instructions on how to replace this stuff, so if you have any tips, I would appreciate it.

I know I asked a lot of questions, so here's a recap:

1. When the sensor light comes on, should they be replaced immeditely, or do they give you some time?

2. What visual clues do I need to look for regarding rotor wear?

3. Metal tabs on brake pads?

4. E36 or E46 for a 1999 323i?

Thank you in advance for any help. I the Pontiac board to help me replace the turning signal switch in my car a couple of months ago and everyone was so helpful.

Thanks,

GT

I think I answered one of my own questions. It is a 1999 323i Sedan, so it is an E46 with an M52 engine I think.

Hello,

1. When the sensor light comes on, it's pretty close to end. I'd replace them within the next week or two. (Tip - Next time replace the pads before the sensor wears and save yourself about $25. Since the light came on, you will also need to replace the sensor.)

2. If using original BMW parts, I've noticed that the pads last about 40k miles and I've noticed that the rotors last about 80k miles. A good rule of thumb would be to replace the rotors after every other pad change. As the rotor wears, you will notice a large ridge between where the pad rubs and the edge of the rotor. Another, more scientific way is to measure the thickness of the rotor and see if it's within spec.

3. Break pads for this car don't have metal tabs. It uses an electronic wear sensor instead. When the pads wear down, the sensor rubs against the rotor causing an open circuit making the light come on inside the car. You can reuse the wear sensor ONLY if it hasn't been worn through.

Anthony

Thanks Anthony!

How would I measure the rotors?

Here is the link that will help you with your project:
http://www.bimmerdiy.com/e46
Note that it is suggested that you do the brake pads bedding in procedure to obtain the maximum performance. This procedure is also in the link. Regarding the rotors, if you are reusing the old ones, it is best to have them turned. The machine shop should know if they are still ok or need new ones. I heard that BMW rotors are soft and turning them is not recommended. As for me, I always replace the rotors ($90+ each including the hex bolts) everytime I replace brake pads. Of course, I don't replace brake pads that often. I replaced (first time) the front ones for my 2000 E39 after 120k miles, rear brake pads are still good. I replaced (first time) the front ones for my daughter's 2000 E46 after 85k miles, rear pads still good. I guess depending on how you drive. Lastly, I always need a new sensor ($20 each) everytime because I wait until the brake pad warning light comes on before replacing pads. I could avoid needing new sensor by replacing pads sooner, but I'm not sure if that really saves me the $20 considering the pads are still ok until the sensor light comes on. Good luck and best regards.-Peter

Thanks Anthony!

How would I measure the rotors?

You can use a micrometer. Another option is to bring the rotors to an auto parts store and have them turned, however, apparently the thickness specification is such that turning them would probably make them too thin.

BMW rotors and pads tend to be quite soft too, so they wore pretty quickly on my 2001 325i. (40k for the pads and 80k for the rotors.) They also generated a lot of dust. After 80k I replaced my rotors and pads with after market (Akibono pads and Black Label rotors). Much cheaper and do not generate nearly as much dust. Since I don't drive my BMW like a race car, I haven't notice any performance issues using the after market brakes - and I sure do like not having to clean my wheels every 3 days.

Thanks everyone. Those were all helpful hints. I finally got a chance to look at them tonight. It's the front brakes. The sensor wire is kinked right at the contact point of the calper and apears to be broken. The pads are also very thin. This is all from the drivers side of course. I guess the rear brake sensor wire is on the passenger side. Those pads and wire look fine to me.

So, I know I need new pads and a new sensor wire, but I am trying to figure out if the rotors need replacing. From all the advice I've seeked out and my own visual inspection they look like they are fine. I guess I will just take them in and get them turned and hopefully the guys there will agree with me. If not, I guess that will just mean more downtime for the wife's car while I order new ones. Worst case is we have to carpool for a few days.

I know the front and/or the rear brakes and pads have been replaced in the last couple of years, back when we started dating, but of course she doesn't have any paper work and can't remember the maintenance history of her car, so I am going to call around and see if can get the history tomorrow, so I know how many miles these brakes have on them.

So, know I am searching for places to buy new rotors and a sensor wire. Found several places, but is there a place that the forum recommends?

Thanks again for all the great advice. I am really enjoying learning how to do a lot of the maintenance on my Grand Prix and the wife's BMW.

GT

I called around and found out the front rotors and pads were replaced at 55,400 miles. She is now sitting around 70,700. How long should the front rotors last? Maybe I should replace those.

Well, here is what I bought. Hope I got everything right.

Brembo OEM rotors
Akebono Brake Pad Set ACT Ceramic w/ Shims
Bowa Brake Pad Sensor

They also had some Akebono Euro pads, not sure what the difference is, hope I got the right ones. I upgraded the pads in an effort to cut down dust, because it is terrible right now.

Interesting comments here, ...

My experience with OEM pads over 3 series of BMW has been far worse than what I've seen described here. On OEM Pads I average between 20-30K KM between shop visits. Cars have been an 86 325e2S, an 96 318i and the current 2000 323i automatic (E46). All were bought new. I have contacted BMW regarding this and been told that this was normal for "high performance" brakes such as those that BMW uses. As a point of information, my first oil service with the latest car was 10,000 KM AFTER my first brake job.

In all cases, after having given up on OEM parts and going 3rd party, I now seem to get at least 100,000KM out of a set of brakes, and the rotors seem good enough to be turned for a second time 'round. I'll let you know when I get them off and check them out with a mike.

The down side is that the replacement brake parts I am using (Wagner this time) cost roughly the same as getting the whole job done at the dealer, including labor. This, of course easily pays for itself as the cost is offset by the fact that I actually get to drive the car rather than having it in all the time to have pads and rotors replaced. :naughty:

As an FYI, I do normal highway driving, and there is NO noticable difference in performance. The brake dust seems just as bad no matter which pads & rotors I use.

Thanks for the advice. Just to sum up everything, I finally replaced these myself a couple of weekend ago. First time doing rotors, but I have done pads before on my Pontiac Grand Prix. Pads are much more complicated than rotors anyway.

Things went pretty smoothly. Made a few rookie mistakes though. Total job time was like 4-5 hours. Afterwards I bedded the new pads and rotors.

While taking off the rotors I noticed they seemed to be in pretty good shape. I'm sure I would have been okay with just replacing the brake pads, but I wanted to be safe so I did everything. I had called the shop where they did them last and they said the replaced the rotors and pads at 55,400 miles. It was a dealership too, so I'm sure they used OEM parts.

My job was done at 71,423 miles. So I figured since the rotors had 16,000+ miles on them and they were OEM rotors, I would just replace them to be safe even though they looked okay. I'll probably just do the pads next time and get the rotors turned since I upgraded from OEM parts this time around.

Total in parts were $200 and 4-5 hours of my time. I saved quite a bit of money and the brakes are still working well 2 weeks later. I have to say it was a successful task. I've already A LOT less brake dust on the wheel from the upgraded pads.

These forums are great btw. That is two successfull jobs I have learned to do myself in the last 3 months thanks to the people here. Probably saved me at least $500 total. Everyone is friendly and knowledgable, especially towards new gear heads like myself.

Thanks again!

GT