DanL

Replacing the pads easy but you need to make sure your rotors are in good condition and not too worn. It's strange that your rear pads would wear out before your front pads and that may indicate a problem. The squeak may be because you have an issue with one of your rear caliper.

Razor1973

From looking at and running my finger across the rotors, they look fine except they both have a small lip at the outer end, which I thought was normal in my case, since the car has 102K miles and the pads do wear the rotors a little bit. Funny thing is the front lips are more pronounced, even though the squeal comes from the rear.

What type of issue could the caliper that causes squealing have and how can I tell? I'm having second thoughts about doing this myself, although I'd really like to. By the way, the squeal only happens when stepping on the breaks and at very low speeds (under 5 mph), almost at a full stop.

DanL

The front pads normally wear faster than the rear. If the rear wore down first it's possible that one or both aren't releasing fully and the solution could be as simple as disassembling the components, cleaning the pins / slides, and the careful application of high-temp caliper grease at the proper locations. Or, if you didn't replace the brake fluid at the recommended intervals you may have corrosion in the caliper piston assembly itself causing it to bind and in that case, you're probably looking at new/rebuilt calipers. My guess is that it's probably the former. In any case, see if your friend has a micrometer or digital caliper and measure the thickness of the rotors to make sure they're still in spec. It's not uncommon for the stock rotors to only last 50-60K miles, even less if you drive very aggressively. The minimum thickness for the rear rotors on your car is 22.4mm (.8818 inches). If you have a Harbor Freight nearby you can pick up a more than adequate digital caliper (accurate to within .01mm) for $12 right now or a digital micrometer for $20.

Razor1973

You totally lost me there.As excited as I may have been about changing my own brake pads for the first time, I am really thinking mechanic at this point. LOL And I bought the car with 88K miles 9 months ago. I have no idea what was replaced or when, unfortunately. I only have those 2 photos (end of last page of this thread) to go by.

DanL

It's easy, especially if you're only replacing the pads, and there are lots of DIY guides out there. If you can't find instructions for the E60 just use the E90 guides -- the brakes are the same. In fact, I'm sure you can find step-by-step directions in the DIY forum on this site.

Razor1973

Yeah, just replacing the pads is alright. My concern after what you said is that the squeal may not be from the pads and I won't know how to determine where it's coming from, much less fix it.

DanL

Jack the rear of the car up, make sure the parking brake is released, depress and release the brake pedal and then spin each rear wheel by hand. You'll be able to tell if the brakes are grabbing. If they aren't, your calipers are probably OK and the squeal may go away by simply replacing the pads and cleaning / lubing the components per the DIY instructions you've found. But if it was me, I would also flush the brake fluid (also easy to do) and make sure the rotors are the proper thickness. BTW, if you do the pads yourself, make sure you have the correct tools on hand. For example, you'll need a hex bit to remove the pins but I can't remember what size it is (7mm?)

Razor1973

OK, so I have carefully reviewed all of your comments and I'm trying to summarize all components I need as to buy them by the time the parts get here next week. Keep in mind I'm not technically inclined and have never done work on my cars, but I can also follow directions. Always assume I don't have any tool required, no matter how common it may be in your garages. LOL

Crankshaft Position Sensor:

1. Sensor and has been ordered and is on its way. I already have O-ring torx bolt.
2. E8 torx socket required.
3. Extensions required.
4. Long Mechanic's magnet required.
5. Small flat head screwdriver required.
6. Flashlight required.

Brakes:

1. 4 break pads and 2 break pad wear sensors ordered and on their way.
2. Recommended that I measure rotor thickness to make sure they meet minimum requirement. I did not know Harbor Freight and I just fount out they have 2 stores 20-25 min from me each and they have the digital micrometer in stock for $21. Thanks a lot!
3. Recommended that I cleaning pins and slides. I just have no idea what those are, how to clean them or what I'll need.
4. Recommended that I apply high-temp caliper grease at the proper locations. Same as above. (Sorry.)
5. Recommended that I replace brake fluid. Sounds easy enough. Any type of fluid I should be looking at or the cheapest one will do?
6. Hex bit to remove the pins required. Which one should I buy? I hope I can find it locally.
7. None of the 3 DIY videos I watched on YouTube mentioned anything about cleaning pins/slides, applying caliper grease or a hex bit. I was hoping you'd know of a more complete one (or guide) you could link here.
10. Please see attached photos of my rotors. Maybe they can tell you something that may help me.
11. By the way, besides the squeal that definitely sounds like friction, there's a very short whistle-like sound that happens when I press the break pedal that doesn't really sound like friction (I may be wrong). That worries me too. I hope all I'm planning on doing takes care of this too.

Thank you, thank you, thank you again!

Front rotor photos: A, B
Rear rotor photos: D, E, F

DanL

This was one of the first videos that popped up when I searched on Youtube. It shows you pretty much everything you need to know, including what tools you'll need. You can skip a lot of it since you won't be replacing the rotors. It shows you the pins, what areas to clean, etc.

Front and Rear Brakes, Rotors and Wear Sensor Replacement BMW 3-series - YouTube

The 7mm hex (allen) bit socket can be picked up at Harbor Freight as well. A set of six only cost $8 right now:

6 Piece 3/8" Drive Metric Hex Bit Socket Set

You said you had a friend who was going to help you and who has replaced brake pads before. If so, you shouldn't run into any problems.

Razor1973

Thank you. What about the brake fluid and the photos of my rotors?