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  #1  
Old 08-05-2002, 10:19 PM
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Join Date: Apr 2002
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Rear Brakes Lock

On my W123, lately the rear brakes have been locking on good amount of pressure, I'd say the amount of pressure is slightly before slaming them on. The did it with the 195/65/r15s more than with the 235/45/17s now. The rear hoses have a crack on them where it attaches to the caliper. I got new rear hoses, and I ordered new front ones so I could do it all at the same time. Do you think this is causing the problem? Maybe do the calipers need to be rebuilt?
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No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #2  
Old 08-05-2002, 10:53 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Does the car jerk when you stop, or can you make it stop so gently that you can't really tell when it stopped moving by letting up on the brake as you get close to motionless?

If it always jerks, even with very light pedal pressure, the rear calipers are sticking (or the fronts, or both).

If the rears are locking up, I'd suspect that the fronts are sticking and you are braking with the rears only!

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #3  
Old 08-05-2002, 10:56 PM
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Join Date: Apr 2002
Posts: 3,469
Peter, Excellent information. I can stop from like 40 and push down pretty hard, then let up so the car doesnt even jerk or move back and forth. The front calipers may be sticking. You have an excellent point. How can I test to see if the fronts are sticking? The car dives like it should when I brake hard. So I dont get it.
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #4  
Old 08-06-2002, 03:53 AM
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Join Date: Apr 2002
Posts: 3,469
I went out to do some testing.
THe car dives down when you put on the brakes hard leading me to believe that the front brakes are working. I did some hard stops and figured the skidding was occuring from the left rear. I got out and checked. I felt the wheels, they were all hot...I touched near the hub part of the discs, and I felt radiant heat from all of them. i got out my pen light and i noticed that the rear pads look kinda low. I am going to take them out and look tomorrow. I have a caliper rebuild set for the front, but I wanted to paint them first. I do have new rear lines. I bet that I need new rear pads. I will look tomorrow. Thanks
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #5  
Old 08-06-2002, 07:52 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Austin:

Before you change pads, check the rotor thickness. The part the pads runs on starts out higher than the center, and is machined straight out to the edge. When they are worn out, there will be a noticable lip at the outer edge, where the pads don't over the edge, and the center section will be flush the the machined portion. If the rotors are this thin, replace them, since the pads will contact the anti-rattle spring when they wear down if you don't . When this happens, the pistons are forced sidways in the bores, and cock, then stick and gouge the chrome plating and/or drag badly and roast all the rubber bits.

It actually sounds like your brakes are working properly -- if you are actually dragging the tires, slow down some and brake earlier -- it takes some effort to lock the wheels on a Benz, and if you are, you are DRIVING TOO FAST for conditions, and will surely end up like my friend's son -- we always thought he was going to stop just a second late sometime, and he did -- totaled his 300 Turbo hitting a stopped car in front of him! Terrible waste of a car that looked and ran nearly mint.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #6  
Old 08-06-2002, 08:37 PM
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Join Date: Apr 2002
Posts: 3,469
I talked to my friend. He said that the master cylinder is probably getting stuck.

My rotors and pads are all in good shape. I am going to replace all the rubber hoses, flush the system. My old calipers were leaking, so I am going to rebuild those, and then look at the rear. Sometimes when the mastercylinder is bad, the rear brakes cook like you talked about, so I may have to rebuild those. For now I am going to park it.

I am going to replace the master cylinder, the rubber lines, the brake fluid. Ill keep you posted. Thanks
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #7  
Old 08-06-2002, 08:52 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Austin:

If you had fluid leaking from the front calipers, you had only rear brakes! You may be quite surprised at how much better they work after you rebuild them.

Calipers are easy -- you can "lift" the piston out with a pair of screwdrivers to remove them. Make sure you coat the new seal with brake fluid before you put it in, and make sure you have the piston aligned properly before you push it back in, it's a pain to rotate it once it is in place. There are actually one three parts on each side -- seal (square, goes inside), dust boot, and heat shield. The heat shield will help you get the piston in correctly, it won't fit if the piston is rotated wrong!

Use a sharpened popsicle stick or plastic something to pry out the old seal - if you use a steel implement, you will scratch the bore and cause trouble.

Flush out all the old brake fluid and I think you will find the master cylinder is fine -- only if you have a brake pedal that drops to the floor and doesn't use brake fluid would I suspect the master cylinder.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #8  
Old 08-07-2002, 03:06 AM
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Join Date: Apr 2002
Posts: 3,469
I have a 82 300D thats blown up that I use for parts.

My 300CD calipers in the front started leaking, so I switched them with the 300D parts car. I got a rebuild kit for my front brakes which I will do this week along with the other improvements listed above. I may rebuild my rear brakes to be sure so I wont have to deal with it.

My front calipers now are from my 82 300d, and they dont leak, but the rear brakes from my 300cd are still on the 300CD and they lock. I am thinking the master cylinder still.
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #9  
Old 08-12-2002, 02:41 AM
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Join Date: Apr 2002
Posts: 3,469
I got new hoses for my car. i am going to put them on tomorrow and let you know how it goes.

What are the biggest front brakes mercedes that will fit on my car? W126 560 SEC or 560 SEL or 300 SDL right?

What about rear? I was thinking of doing some brake upgrades instead of rebuilding my calipers.
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
Reply With Quote
  #10  
Old 08-12-2002, 08:08 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Austin:

Use the original calipers, the others won't fit. You have PLENTY of brakes, these cars will stop as well as any will with factory brakes. If you've never driven on the Autobahn, you may not understand -- NO German car will have brakes the end user can improve, if they did even more people would get killed! The factory brakes will haul that CD down from 110 mph is less distance than you might believe,

Rebuild the original calipers and make SURE you have good rotors -- if they are thin, the pads can jam and stick the pistons -- resulting in very poor brake operation. Mismatching calipers and rotors, or calipers and backing plates will cause you endless trouble.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #11  
Old 08-17-2002, 01:14 AM
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Join Date: Apr 2002
Posts: 3,469
Rear brakes fixed with master cyl and lines

I was trying to get stainless steel lines, but I couldnt get them. I think that I am going to figure if 300E lines can fit my car then do a group buy so if any one is interested let me know.

I put on the regular ATE ones for now and an Ate master cylinder. The brakes are very firm. However I think that my driveshaft center support broke because it sounds like the drive shaft is clanking around.

Any ideas...im going to post another thread probably
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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  #12  
Old 08-17-2002, 02:55 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Austin:

Drive shaft mount or flex disk? Either could b bad. Check the mount by shaking the drive shaft -- if you can move it in the mount, the rubber is bad.

The flex disk goes between the driveshaft and the transmission (or diff, but that one rarely goes bad) -- and signs of distortion or cracking means replace it, the drive shaft can come loose if the centering sleeve goes , too.

If the flex disk is bad and you have thumping noises while driving, get a new centering sleeve, too, it will be broken and allow the driveshaft to move too much. Get the grease that goes in it, too!

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #13  
Old 08-17-2002, 03:15 PM
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Join Date: Apr 2002
Posts: 3,469
yeah, flex discs are fine, but I can move the driveshaft up and down so its the driveshaft support. I was planning to get the bearing and the support and do them at the same time next week. It makes a clunking noise and shifts hard.

What grease are you refering to? I have mercedes wheel bearing grease.
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
Reply With Quote
  #14  
Old 08-17-2002, 04:32 PM
Registered User
 
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Austin:

Mark the front and rear halves of the driveshaft before you pull the front off to change the bearing and carrier. You MUST get it back EXACTLY as it was before, or you risk serious vibration. It is not, alas, keyed like the Volvo, where it will only go in one way!

You don't need any grease for the carrier or center bearing, the drive shaft is non-servicable except for replacing the bearing and carrier.

The clunk and hard shifting are most likely a vacuum leak resulting in low vac to the transmission modulator. Look up the numerous postings on this subject. The driveshaft if fine unless you get a "bad muffler" noise that is not a bad muffler, accompanied by floorpan vibration centered just at the rear of the front seats. If you can feel the floor vibrating when you put your hand on the drive tunnel at speed, you have a bad carrier bearing mount or other driveshaft problems.

If the car just bangs hard when it shifts, sounds like the rear end is thumping around, you have a vac problem, not a driveshaft problem, leave the driveshaft alone!

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
Reply With Quote
  #15  
Old 08-17-2002, 05:01 PM
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Join Date: Apr 2002
Posts: 3,469
Driveshaft carrier bushing is bad. I am going to replace the driveshaft support and the bearing on the drive shaft. I now know to mark the driveshaft because on my sedan that I have also, I pulled it apart without marking it. Im going to leave it in my coupe until I get the parts.

The grease is it for the little "pilot bushing" where the differential pinion yolk slides into the driveshaft? I need to call the parts in on monday so let me know about the grease
__________________
No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.
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