Rear brake maintenance gone bad

[Espen]

Well I figured it was time to get some new rear brakes.

The old ones looked like this:

http://filserver.pyrabel.net/bilder/e34/bremser/old.jpg

So i bought new disc`s, pads, and sliders.
http://filserver.pyrabel.net/bilder/e34/bremser/slider.jpg
New sliders..

The old ones were like total crap, the pads were full of cracks. And fell apart as soon as i got the pads out of the calipter.
http://filserver.pyrabel.net/bilder/e34/bremser/old2.jpg

Looks better huh?
http://filserver.pyrabel.net/bilder/e34/bremser/new.jpg

[Espen]

But wait.. After a 5km test drive it smells like hot brakes..
http://filserver.pyrabel.net/bilder/e34/bremser/hot.jpg
Those were damn hot, thats for sure!

They must be hanging on... How can this happen??? Sliders are new and well greased. It also looks like the pads only touched the disc at the very outside of the disc.

http://filserver.pyrabel.net/bilder/e34/bremser/ytterst.jpg

[joshua43214]

I can't really tell much from the picture of the new rotor, but the picture of the old rotors show a definate problem.

Unless the car has been sitting for a very long time, the rear brakes apear to not be aplying. Brake hoses can be a common cause of this. Try starting the engine and very firmly aply the brakes. Shut off the engine and release the brake and see if you can freely turn the wheel. You should be able to rotate the rear wheels back and forth with no resistance taking up the differential slop each way. crack open the bleeder and see if the wheel suddenly frees up, if so, replace the lines.

If you assembled the slides into the mount before the caliper, the pads bay not be sitting properly on the mount, causing drag as well.

It is not unusual for the pad to only make good contact with the outer edge of the rotor until they are worn in. How hard did you get on the brakes on the test drive? many folks try to "burn in" the brakes too aggressively and smoke the brakes test driving them. The pads should be well seated before any attempt to burnish them in, 5km is just enough distance to seat them, not enough for using them hard.

[Espen]

The test drive was maybe a bit longer, i applied brakes very hard at once, i was told this was nessecary to seat the pads. I use the car to work today. (6km) Didnt get as hot as yesterday, but the left rearwheel was a lot hotter than the right one, wich was not hot at all.

the old rotors shows that only a small stripe of the pads are applying. the car was sitting the whole winter before i bought it.

The picture of the sliders is "lying" I did it like that first, later on when i tried to fit the new pads i realized that i had to first fit the "claw" on the back of my hub, then place the pads into the caliper, then connect the caliper and the "claw" together with the sliders.

I dint get your point when it comes to the conclusion that the lines must be changed. I start my engine and apply the brakes. stop engine, and try to push the car forth and back, i can feel the brakes are hanging on. Is this because of bad brake lines? I though it could be because the piston was not going all the way back.

You mean that it still is pressure in the system causing pressure on the pads against the discs? Im not so familiar with brake systems, how can bad lines cause the pressure not to go back when the brakepedal are released?

[genphreak]

Is it my imagination or is the right one the one that was really bad in the first pics? Is it possible that the caliper could be warped causing the pad to engage on the inside of the rotor (even when the brake pedal is not being applied) and not engage at all on the outside, causing that heat zone/heavy wear effect? Man I don't know how you could have survived on those pads the way the first lot looked.... ouch! Class pics btw :)

[joshua43214]

Sliding calipers always aply more pressure to the outer edge, that is why many people prefer fixed calipers since they aply more even pressure to the pad.

In practice, sliding calipers work fine for anything except for hard raceing since once the pad is worn in, it will just continue to wear at a slight angle. If the pad makes contact onthe inner edge of the rotor before the outer as shown in the old pic, it indicates a binding or dragging problem. Many shops would take one look at those rears and just quote calipers and hoses right off the top.

[Omega]

It looks like one of your calipers is not working correctly. The wear patterns on the old discs are not the same.

I would guess that looking at the photo of the old discs the one on the right is the caliper that is causing an issue. The disc looks heavily scored. I would also question the wear pattern as it looks like the groove is quite deep so this has happened over a long period of time.

If you are sure that the caliper slides and that the caliper piston will go in and out with no resistance, then check the flexible rubber brake hoses as Joshua recommends. These can sometimes collapse internally with no visible external damage.

[Espen]

The first pic is mirrored, you can see the exhaust part, the exhaust is on the left side of the car, it was mirrored as i took an "before" pic on the left side, and a "after" pic on the right side, easier to compare pics when they are of the "same side".

the calipers slide ok, the sliders are changed, the old sliders were not that bad though. It could be a binding piston, the old pads were very thin, so the piston have not been completely compressed for a long time. It may have caused rust and such. The brake fluid doesnt look good either, I think ill wait a couple of days, keeping an eye on the rear breaks and see if the problem still is there, if it dissapears, OK. If not, ill try to change my hoses and fluid. Still bad, then Im gonna pop out the pistons and check the inside of the caliper.

[genphreak]

Sliding calipers always aply more pressure to the outer edge, that is why many people prefer fixed calipers since they aply more even pressure to the pad.

In practice, sliding calipers work fine for anything except for hard raceing since once the pad is worn in, it will just continue to wear at a slight angle. If the pad makes contact onthe inner edge of the rotor before the outer as shown in the old pic, it indicates a binding or dragging problem. Many shops would take one look at those rears and just quote calipers and hoses right off the top.Thank you Joshua, it is awesome being able to share knowledge from people like you on this board. Nothing beats the strength of practical experience on these cars, especially facing the likes of troublesome old calipers and stuff. I mean it when I say a big thank you for the contributions you make (and those of so many others with similar kinds of experience) that the more inexperienced but nonetheless lucky members like me get to read, learn and apply on our great and loved German beasties. :) Nick

[Javier]

fluid go forth but not back.

Javier

[Espen]

Clogged flex lines som times act as check valves. ...
fluid go forth but not back.

Ill try to release the bleeder after applying brakes, and see if that causes the pads to release.

[632 Regal]

changing the brake fluid is periodic maintenance because it attracts water and can rust the oistons. Another thing to check besides replacing the flex lines is the little rubber bushings that the sliders go into. you are NOT supposed to greaase them as it can deteriate the rubbers which can case the calipers to sit all crooked...kinda like yours seem to be doing.

[Espen]

changing the brake fluid is periodic maintenance because it attracts water and can rust the oistons. Another thing to check besides replacing the flex lines is the little rubber bushings that the sliders go into. you are NOT supposed to greaase them as it can deteriate the rubbers which can case the calipers to sit all crooked...kinda like yours seem to be doing.

Interesting, I changed the rubber bushings yesterday as well, filled up the sucker with heat resistant copper grease.. my english is still poor, what does "deteriate rubber" mean?

[632 Regal]

detriorate rubber means the rubber hoses are trash, this can be confirmed with the bleeder release test your going to do.

[ttsalo]

The test drive was maybe a bit longer, i applied brakes very hard at once, i was told this was nessecary to seat the pads. I use the car to work today. (6km) Didnt get as hot as yesterday, but the left rearwheel was a lot hotter than the right one, wich was not hot at all.


I have new BMW rear brake pads and Zimmermann rotors waiting to be installed, and the pads came with a note warning NOT to brake hard in the first 200 kms after the installation!

My current rotors look much like yours looked. The pads are not applying properly on both sides. I'll be changing them during the weekend.

If the sliders are OK, my bet would be on pistons sticking in the calipers because of light corrosion. Flexible brake lines deteriorating into a sort of a one-way valve and causing the brakes to drag is not exactly a common occurrence.

[Espen]

detriorate rubber means the rubber hoses are trash, this can be confirmed with the bleeder release test your going to do.

Hmm this didnt make things clearer...
"The rubber hoses are trash" You mean the rubber bushing that the sliders go through? I cant see why a bit of grease can make them break.
And how can I confirm this with the bleeder test? i thought the bleeder test only confirmed that the brake lines were busted..

[632 Regal]

sorry, i was referring to the brake lines. The sliders are supposed to be installed clean and dry so in reality you should clean the grease out.


Hmm this didnt make things clearer...
"The rubber hoses are trash" You mean the rubber bushing that the sliders go through? I cant see why a bit of grease can make them break.
And how can I confirm this with the bleeder test? i thought the bleeder test only confirmed that the brake lines were busted..

[Espen]

Tried to open the bleeder, no luck, the bleeder bolt snapped off, and i got a leak. Took off the calipter, ordered a new one.. I guess that combined with new brake fluid will help a lot.

Also tried to disconnect the rubber hose, got it off from the caliper, but not in the other end. to much rust, and the bolt gor rounde. So i blended the brake line and drove home with my caliper in the trunk.

[Javier]

you will have a good time bleeding the system!

Javier

[Kalevera]

Just seeing the wear pattern on the old rotors indicates that the car sat for a while, then was driven with partially locked calipers and possibly loaded pads. After a car sits for some time, the pads and rotors can usually be heat cycled and used; sometimes not.

Rebuild the calipers. I wouldn't even drive the car until it gets done -- dangerous and damaging. The heat will ruin the pads and the rotors.

Use a wire wheel to clean any non serious rust on the piston surfaces. I also like to use a pumice hand cleaner to give them a once over.

[Espen]

you will have a good time bleeding the system!

Javier

Yeah Im afraid of that. I plugged the lines so good, that i cant have gotten much air up the lines...

Well, now im off to get my new calipter.

[Espen]

Old calipter:
http://filserver.pyrabel.net/bilder/e34/bremser/oldcalipter.JPG

old piston:
http://filserver.pyrabel.net/bilder/e34/bremser/oldpiston2.JPG

New vs Old
I bought it from a company who "buy" your old OEM calipter, give it at overhaul, and sell it. So what i got is in fact an used OEM calipter who has been total rebuilded. Very cheap also.
http://filserver.pyrabel.net/bilder/e34/bremser/newvsold.JPG

2
http://filserver.pyrabel.net/bilder/e34/bremser/newvsold2.JPG

[Espen]

Finally
http://filserver.pyrabel.net/bilder/e34/bremser/final.JPG

My bleeder, very handy..
http://filserver.pyrabel.net/bilder/e34/bremser/mybleeder.JPG

[632 Regal]

dude that rust is really bad! is the whole underside of the car like that? If it is I would not hesitate in upgrading to a whole other E34 without rust.

There are only 2 things that kill these cars, rust and accidents.

Sweet bleeder setup man!

[Espen]

Here in Norway they use like 10ton of salt pr 10km road on the winter.. The calipters have never been painted, so its a easy target for the salt. I have no rust under my car, it have been well maintained with techtyl, and oil treatments. I had some rust on the front wing and some under my right reardoor, have fixed it all, cut`n weld. Its no rust on it at all now.

[Kalevera]

Brilliant idea for a brake bleeder!

[Espen]

Brilliant idea for a brake bleeder!

Didnt work to well though.. The brakefluid reservoir (bad spelling?) started to shake, and a fog cloud of brakefluid came out from under the reservoir. To much pressure in the tire maybe?

[BillionPa]

you want to get some Speed Bleeders, greatest invention ever

and you should rebuild the other caliper so the wear pressure is the same.. or buy a new one of those too.

the only lube you should use on the guide pins is the dark green permatex stuff.

that is some sweet nickel plating on that new caliper.

invest in an 11mm flare wrench by the way.

[Espen]

Ill buy a new one on the other side as soon as my paycheck arrives... My mastercard have gotten enough beating this month ;)

What is a flare wrench?

[BillionPa]

it wraps around the bolt on so its attatched on all 6 sides.

it helps grab the 11mm nut screw on the steel brake line so you dont strip it