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Suspension & Braking Forum by BimmerWorld
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Old 04-06-2014, 11:05 AM   #1
Alekm
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Caliper pressure when putting new pads

I noticed on few occasions recently that the rear driver side wheel was getting too hot. There was some slight rubber burn smell.

So while doing a brake job to replace rotors and pads, when trying to press the caliper, it would not budge. I even broke my C clamp while trying . So I need a new caliper, ordered one from bavauto, and while doing all this, given the age of the car I decided to replace the brake lines as well. It was odd that the pads on the other rear side were so unevenly worn. Maybe 1/3 compared to the side with the stuck caliper which was almost all gone.

Now, my question is how tough should the caliper resistance be when trying to press them. The front two were bit tough but was able to press them completely to make space for the new pads. The other rear caliper was very easy to press. I am wondering if there is a way to diagnose when the calipers may start to fail and if it is worth to replace them all.

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Old 04-06-2014, 11:09 AM   #2
shovelit
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Steady even pressure should do it. I always replace them in pairs.
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Old 04-06-2014, 11:55 AM   #3
ChuckyVee
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Quote:
Originally Posted by Alekm View Post
I noticed on few occasions recently that the rear driver side wheel was getting too hot. There was some slight rubber burn smell.

So while doing a brake job to replace rotors and pads, when trying to press the caliper, it would not budge. I even broke my C clamp while trying . So I need a new caliper, ordered one from bavauto, and while doing all this, given the age of the car I decided to replace the brake lines as well. It was odd that the pads on the other rear side were so unevenly worn. Maybe 1/3 compared to the side with the stuck caliper which was almost all gone.

Now, my question is how tough should the caliper resistance be when trying to press them. The front two were bit tough but was able to press them completely to make space for the new pads. The other rear caliper was very easy to press. I am wondering if there is a way to diagnose when the calipers may start to fail and if it is worth to replace them all.

Thanks,
You took off the cap from the fluid resvervoir when pressing in the caliper piston correct?
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First Bimmer..."Miss December"...2000 323i, purchased Dec. 2013 w/82K on the clock. PM thus far...pads/rotors, belts/pulleys, complete CS overhaul, FCABs, plugs, autotranny/differential service. Emergency repairs...PS pump, turn signal stalk, CPS, Ignition Coil #2 cyl, electric aux fan.
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Old 04-06-2014, 12:07 PM   #4
Alekm
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Originally Posted by ChuckyVee View Post
You took off the cap from the fluid resvervoir when pressing in the caliper piston correct?
ooops, no I did not. Maybe that explains the harder than expected pressure that I was getting. Don't remember having that much hard time when I did the brakes 6 years ago.

Would that cause any problems to the remaining calipers or abs system?
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Old 04-06-2014, 05:41 PM   #5
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Originally Posted by Alekm View Post
ooops, no I did not. Maybe that explains the harder than expected pressure that I was getting. Don't remember having that much hard time when I did the brakes 6 years ago.

Would that cause any problems to the remaining calipers or abs system?
Your brake fluid system is a sealed system to all intents and purposes although its not air tight. Leaving the res cap on would certainly cause problems when trying to push the piston back into the housing. The other thing, of course, is that the pressure you applied using the G clamp would be borne by the seals on the other calipers and the master cylinder so there is a possibility of damage to seals under such circumstances, I suppose, depending on how old and worn they are. Check you fluid level daily after you have completed the job for the first couple of weeks. Caliper pistons can rust up if the rubber boots split. Probably why they were problematic.
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Old 04-06-2014, 05:44 PM   #6
racin366
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For the rears on most cars the caliper needs to be rotated to compress, not pushed in due to the e brake. I am not sure if this applies to BMW, IIRC they may use a different type of e brake setup that makes this info useless.
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Old 04-06-2014, 06:04 PM   #7
RayPooley
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Originally Posted by racin366 View Post
For the rears on most cars the caliper needs to be rotated to compress, not pushed in due to the e brake. I am not sure if this applies to BMW, IIRC they may use a different type of e brake setup that makes this info useless.
Why would you need to rotate the caliper to press the piston in? Doesn't make sense. The hand brake is a cable operated drum brake. Nothing to do with the caliper or the hydraulic system. Totally independent of it in fact.
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Old 04-06-2014, 06:30 PM   #8
Alekm
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Originally Posted by RayPooley View Post
Your brake fluid system is a sealed system to all intents and purposes although its not air tight. Leaving the res cap on would certainly cause problems when trying to push the piston back into the housing. The other thing, of course, is that the pressure you applied using the G clamp would be borne by the seals on the other calipers and the master cylinder so there is a possibility of damage to seals under such circumstances, I suppose, depending on how old and worn they are. Check you fluid level daily after you have completed the job for the first couple of weeks. Caliper pistons can rust up if the rubber boots split. Probably why they were problematic.
That makes sense. The system is 15 years old, so hopefully there is some leakage. I will be checking in the fluid levels once the job is completed.
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Old 04-06-2014, 07:25 PM   #9
jdstrickland
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Originally Posted by racin366 View Post
For the rears on most cars the caliper needs to be rotated to compress, not pushed in due to the e brake. I am not sure if this applies to BMW, IIRC they may use a different type of e brake setup that makes this info useless.
It's a PARKING BRAKE, and it's completely separate from the service brakes.
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Old 04-06-2014, 07:29 PM   #10
racin366
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Why would you need to rotate the caliper to press the piston in? Doesn't make sense. The hand brake is a cable operated drum brake. Nothing to do with the caliper or the hydraulic system. Totally independent of it in fact.
That is what I thought, but on many cars the e brake is just a cable that tightens the rear calipers, so to compress them when changing pads you have to turn them like a screw, squeezing won't work and may damage the caliper.

Sounds like OP may have a bad caliper.
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Old 04-06-2014, 07:30 PM   #11
tkrotchko
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Originally Posted by RayPooley View Post
Why would you need to rotate the caliper to press the piston in? Doesn't make sense. The hand brake is a cable operated drum brake. Nothing to do with the caliper or the hydraulic system. Totally independent of it in fact.
There's a couple manufacturers who do this. Honda is one. One of the swedish brands as well.

But BMW does NOT require you to rotate the rear piston.
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