illuminate me, brake masters. - PeachParts Mercedes-Benz Forum

fochs · #1 11-23-2011, 11:57 AM

I replaced the front brake system on my 83 240d yesterday with new hoses, reman calipers new rotors, padsand wheel bearings. After bleeding, my front brakes are still dragging. Cracking the bleed screw does nothing to eliminate the drag. Did I get a bad set of calipers, or is my master cylinder to blame? How does the master cylinder work on these cars? is it likely for just the front brakes to drag due to m.c. issues? I ordered a new master cylinder, but would be really pleased know if anyone has any other ideas or insights.

tangofox007 · #2 11-23-2011, 12:07 PM

The pads on disk brakes always "drag" to a degree. New pads make it more noticable. Could you further illuminate "dragging?"

If opening a bleed valve makes no difference, the likelihood that the master cylinder is at fault is very close to zero.

leathermang · #3 11-23-2011, 12:08 PM

Are your calipers full floating or something else ?
Can you determine if the contact is more on one side of the rotor than the other ?

tangofox007 · #4 11-23-2011, 12:15 PM

Quote:

Originally Posted by leathermang

Are your calipers full floating or something else ?
Can you determine if the contact is more on one side of the rotor than the other ?

Does your W123 have floating calipers? (For sure, it didn't leave Stuttgart with them.)

Or is it so dry in Texas these days that even calipers won't float?

fochs · #5 11-23-2011, 12:36 PM

I do not know what a floating caliper is? The calipers are bendix. I compressed the pistons using a quick clamp on the tabs on the pads, and have noticed no marked difference on either side, on either wheel. I performed the operation at least 5x per side, spinning after each piston compression inner and outer. The hub spins easier after one piston and freely after both, until I actuate the brakes. I changed out the clips to my originals and the wheels seemed to spin fractionally better- but I'm not positive of that result, could have been wishful thinking by that point.
Can one lubricate the caliper pistons?
Fixed type caliper, after further review- one piston per side.

tangofox007 · #6 11-23-2011, 12:45 PM

Quote:

Originally Posted by fochs

The hub spins easier after one piston and freely after both, until I actuate the brakes.

Then what happens? Is the wheel impossible to rotate by hand? Or is there just noticable drag? Some drag is normal; with new pads it's a lot more "normal." Unless the wheel is "locked," you probably do not have a problem.

fochs · #7 11-23-2011, 12:56 PM

Quote:

Originally Posted by tangofox007

Then what happens? Is the wheel impossible to rotate by hand? Or is there just noticable drag? Some drag is normal; with new pads it's a lot more "normal." Unless the wheel is "locked," you probably do not have a problem.

I can spin the wheel using the hub flange, but with some difficulty, Certainly noticeable drag. The wheel is not locked, though.

leathermang · #8 11-23-2011, 12:59 PM

Tango, sometimes questions are designed to determine the starting point of the discussion....

leathermang · #9 11-23-2011, 01:00 PM

With new wheel bearings installed... tell us exactly what procedure and tools you used for that part of the repair...were you reading the FSM at the time you did that or going by what you had done in the past on American cars ?

kerry · #10 11-23-2011, 01:14 PM

Quote:

Originally Posted by fochs

I can spin the wheel using the hub flange, but with some difficulty, Certainly noticeable drag. The wheel is not locked, though.

I'd say it's normal. Drive it and keep track of wheel temperatures with a non-contat thermometer. If the wheel is not overheating, forget about it.

leathermang · #11 11-23-2011, 01:20 PM

Ok.... so you have not driven it since this repair ?
Be sure your wheel bearings are set to spec... which may require a one time use crush ring... on each.... then drive around the block using the brakes ... see if they feel even , check for excessive heat when you get back to the house.... it may just be a matter of alignment by friction and pressure is needed... do your wheel turn test with the tires on .... moving the rotor by hand gives you little mechanical advantage so will seem very hard..

fochs · #12 11-23-2011, 01:24 PM

Quote:

Originally Posted by leathermang

With new wheel bearings installed... tell us exactly what procedure and tools you used for that part of the repair...were you reading the FSM at the time you did that or going by what you had done in the past on American cars ?

I had the new races pressed in and packed new bearings. Tapped in new grease seal. I have not torqued the retaining nut as of now. It is just beyond hand tight and there seems to be no issue there, the rotation is soundless and ultra sooth without the brake. I need to research the dial indicator placement before I finalize that. I will wait to complete until I satisfy the perceived brake issue.

fochs · #13 11-23-2011, 01:32 PM

Quote:

Originally Posted by kerry

I'd say it's normal. Drive it and keep track of wheel temperatures with a non-contat thermometer. If the wheel is not overheating, forget about it.

What kind of temperatures should I expect to see in a nominal condition assuming non-spirited driving ?

Diesel911 · #14 11-23-2011, 01:46 PM

Quote:

Originally Posted by fochs

I had the new races pressed in and packed new bearings. Tapped in new grease seal. I have not torqued the retaining nut as of now. It is just beyond hand tight and there seems to be no issue there, the rotation is soundless and ultra sooth without the brake. I need to research the dial indicator placement before I finalize that. I will wait to complete until I satisfy the perceived brake issue.

When I did mine (front wheels) I attached the Magnetic Indicator Base to the flat surface of the Brake Rotor and positioned the Dial Indicator on; and inlie with the Shaft of the end of the Axle shaft.

DIY Repair Links
http://www.peachparts.com/shopforum/forumdisplay.php?f=82
http://www.peachparts.com/Wikka/DoItYourSelf

Harbor Freight has a Thanksgivings sale coming up. Magnetic Bases and Dial Indicators may be on sale.
The only draw back is they do not sell Metric Dial Indicators so you need to calculate mm to inches.

kerry · #15 11-23-2011, 01:53 PM

Quote:

Originally Posted by fochs

What kind of temperatures should I expect to see in a nominal condition assuming non-spirited driving ?

It depends on outside temperatures and whether you were just using your brakes on a long downhill stretch. Comparable temperatures on all 4 wheels is good. I can't recall seeing anything above about 120 degrees I think.