BMW M5 Forum and M6 Forums banner

1 - 11 of 11 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Greeting all ,

I’ve recently purchased my beast, a March of 2003 build. For the first 5 months of ownership the beast has behaved. Lately I’ve noticed an extremely loud squeal coming from the wheels. At first I figured it was just the performance pads the previous owner installed. Fast forward to a few hundred miles and that squeal evolved into a treacherous grinding scream from the wheels followed but the smell of hot brakes. As I’ve tried to diagnose it, my visual inspecting revealed my front passenger wheel caked in brake dust while 3 other wheels are clean. After searching many threads I’ve come to understand that the caliper Is seized.

Here’s where I’m lost...

The beast was parked for a week and today I’ve decided to take it for a spin to get some gas and keep investigating how bad that caliper is. What I’ve come to understand is when cold, braking performance is normal without noise and pedal feel is strong. 40 miles of cruising with occasional spirited pulls and slowing down, brakes heat up and start making noise again at the 42nd mile after initial start up. I’ve sourced the parts for a caliper rebuild thanks to a few threads, but I can’t understand if it’s absolutely my caliper piston or maybe the pins.

The takeaway from all this :
Normal driving and braking is no issue. After heating up , brakes seize and degrade performance all around. Should the piston be under the scope? Or the pins? Or maybe ... the pad/rotor setup ?
 

·
Registered
Joined
·
5 Posts
Consider doing a brake fluid flush and bleed. It's inexpensive and a good place to start. Since brake fluid is hygroscopic - attracts moisture from air, over time, this moisture makes its way to the calipers and heat transfer from using your brakes causes the moisture to boil causing expansion behind the brake piston that results in a dragging brake.

While you are doing the brake bleeding, it will be a good opportunity to inspect the caliper guides.

Hope this helps!
 

·
Registered
Joined
·
52 Posts
It doesn't really help with the problem, but
I really like to keep things nice and original as far as brake system goes.

I am not a fan of slotted or any other performance brakes.
Just the OE vented discs are well performing and the OE ATE calipers usually cause problems.

I'd recommend returning to OE brakes.

Sorry I couldn't be of any help with the problem
 

·
Registered
Joined
·
393 Posts
Sounds like you should rebuild all your calipers or at least pinpoint which are the worst and start there. That means the piston dust boot, piston O ring and the caliper slides. Fairly easy to DIY.
 

·
Registered
Joined
·
1,518 Posts
I had the similar issues. My M5 would shake when applying brakes hard and it was random each time so I could not diagnose this right away. I decided to replace front calipers after doing all suspension work and came to find out that both front calipers were not in great condition. With new calipers, it actually locked my front wheels pretty hard!

Go rebuild the calipers or replaced with reman units and bleed the brake fluid with ATE type 200 or better.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #7
Thank you all for your replies! New centric caliper pistons and seals are ordered for the front. After I managed to take off a wheels to inspect, the passenger rotor looks like a record that doesn’t play any good music. Decided to go with Zimmerman/akebono kit from FCP.

should slides be replaced to? Trying to budget for all of those “while you’re in there” parts.
 

·
Registered
Joined
·
482 Posts
Might even consider replacing the lines while you're at it. Sometimes depending who's touched those brakes they may let it hang and the line somehow develops a kink then prevents the return of the pistons causing it to seize.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #9
Might even consider replacing the lines while you're at it. Sometimes depending who's touched those brakes they may let it hang and the line somehow develops a kink then prevents the return of the pistons causing it to seize.
Didn’t think of that. But looks like the lines were done by previous owner and they’ve installed ECS lines all around. Visually they look in shape but I’m not sure now you mention it.
 

·
Registered
Joined
·
1,518 Posts
If you like factory braking quality (cold bite), then stick to semi metallic pads like textar/jurid that dusts crazy. Ceramic pads provides great braking but cold bite/braking power action requires more push to pedal. I hated ceramic pads on my E46 when I did the brakes and immediately switched over to semi metallic pads (textar/jurid OE).
 

·
Registered
Joined
·
9 Posts
Discussion Starter #11
If you like factory braking quality (cold bite), then stick to semi metallic pads like textar/jurid that dusts crazy. Ceramic pads provides great braking but cold bite/braking power action requires more push to pedal. I hated ceramic pads on my E46 when I did the brakes and immediately switched over to semi metallic pads (textar/jurid OE).
currently running hawk Hps pads.bite feels good but noise when hot is extremely frustrating. Then again I’m not sure if noise is from pads or the caliper slowly dying on me. Right now I’m just waiting for the replacement caliper piston and rotor and gonna run the pads until they wear down. Looks like they have 60 percent of life left.

any recommendations for pads with performance bite and minimal noise ?
 
1 - 11 of 11 Posts
Top