Brake help needed

[Ericjump]

Just bought a 89 635, it has been sitting for years and is showing over 200,000 miles. I pulled the wheels and of course the rotors are rusty, my questions are: can the rotors be turned to smooth them up? What are the numbers as far as thickness? Any suggestions on new pads? Should I rebuild he calipers? I’ll flush the system with new fluid. Thanks for help and any other suggestions.

[plip1953]

You're best off stripping everything and going from there. But do be prepared for a few issues along the way!

One particular thing you might want to try early in the process is checking that the caliper pistons will move when the brake pedal is pressed. Do this while you can still provide hydraulic pressure rather than trying to do it on the bench. But take care not to pop the pistons right out!!!! Slider pins will quite likely be seized and it might take a bit of heat and a few soft nose hammer blows to help separate the discs from the hubs.

Good luck

[86_6series]

Rotors are very affordable these days that it doesn't pay to have them turned down.
As far as pads go, if your not going to track the car--any oem spec pads should do very nicely
as long as you don't go el-cheapo.

[jps635]

It's pretty easy and worthwhile to completely strip clean and re-kit the calipers. Also think about the MC, booster seals and brake bomb given its been sitting for a long time. Clean any rust off the rotor mounting face of the hubs.

Be prepared the ABS (sensors and toothed hub rings) may also need work, however the ABS works independently of the brake system, and best assessed once the vehicle is mobile, before needlessly upsetting things and causing problems. Typical issues are ABS hub rings if rusty / teeth missing, and the wheel sensors / cables that fail with age.

[Ericjump]

Thanks for the general info, how about some particular info. Does re kit the calipers mean over haul? Where do I obtain rebuild kits? What about ABS, where can I find an explanation of the system, and a troubleshooting guide?
I’m a first time 6er and a aircraft mechanic, don’t mind getting hands dirty but know enough to not to start taking things apart if I don’t know what I’m doing!
Thanks in advance

[jps635]

I see you're new to the car and forum. I've been here for 12-13 years but others have ben here much linger and have a lot more knowledge than me.
This place is a great resource and answers to all your questions can be found here using the search function.
To answer your questions:
- Re -kit. yes overhall, replace the seals etc.
- Where to obtain - See below
- Where to buy see below.
- Info re the ABS system. I have attached a pic form the Bentley manual re the ABS system

In general:
As above the search function works great. 99% of your questions will have been asked and answered in detail. This is generally the first port of call for info.

Get yourself a Bentley 5 Series (E28) manual. Most of the systems are the same
Have a look on the Tech part and there are download manuals I think. (I also have a BMW Workshop manual so don't use)
Also, there is an Electrical Systems Manual (ETM) which I believe can be downloaded. (Once again I have a hard copy)

For parts use this. https://www.realoem.com/bmw/enUS/partgr ... BMW-635CSi . Configure for your specific car and use this to locate/ identify parts. I use and prefer this on-line catalogue but others also use this http://bmwfans.info/parts-catalog/E24/E ... 85/browse/

Where to buy. A number of places and being in the US you are spoilt for choice. I mainly use Pelican Parts, and Autohauz Arizona, and Wallothnesch (Germany), because the y're overseas friendly but may not be the cheapest - there are a number of others that will no doubt be advised.

Have also attached a pdf version of the Norm Grills pages, which addresses a lot of the more common issues