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  #1  
Old 08-03-2000, 05:16 PM
WmHarlow
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I noticed a familiar grinding sound coming from the right rear yesterday on my 240D. I pulled the wheel, ASAP, and found the inner brake pad was 99.9% gone. The outer pad still had better than 75% left on it.

I checked the other wheel and it was not as bad, but still was showing far more wear on the inner pad than the outer pad.

The fronts are wearing about even.

Do I need to rebuild the caliper, or is it better (easier) to buy a re-manufactured unit for the rear brakes? Can these be repaired efficiently. What causes this problem, exactly.

By-the-way, the rotor suffered only minimal scratches... not enough to need resurfacing.

Thanks in advance for info.

------------------
William
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles
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  #2  
Old 08-03-2000, 09:15 PM
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Join Date: Apr 2000
Posts: 166
William,
I experienced the same type of problem on the front calipers of my car. I bought MB kits and repaired them. I found it to be a long painstaking job if you try to do it precisely. If I have caliper problems again, I will probably go to rebuilts. Come to think of it, I don't believe rebuilts were available when I had my problem.

As to what causes it, I don't know for sure, but I suspect that if you don't follow the MB procedure exactly and pull the pads with an impact tool and then press the caliper pistons back with their special tool, you may get the piston "cocked" in the cylinder and it then won't retract when you release the pressure on your brakes. It is like driving with the brakes on all the time.

Another possibility: there is a small rubber rib on the edge of the piston seal that allows the piston to draw back slightly.....it may just wear out.

Hope this helps you somewhat. Good luck.

------------------
Ted
1979 240D
160,000 miles
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  #3  
Old 08-03-2000, 11:16 PM
Jason Alexander
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The best thing to do is replace the caliper with a remanufactured unit. The time involved with rebuilding and the cost of the materials tto do it is more than it's worth. The usual causes for premature caliper failure is not flushing the brake fluid on a yearly basis.

------------------
ASE Master Technician, Lead Technician for Deutsch American Inc. Over 6 years of Import experience-specializing in German Automobiles.

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  #4  
Old 08-04-2000, 12:14 AM
WmHarlow
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Bad fluid probably killed them. I fully bled the system when I bought her, but they were in bad shape then.

Any ideas on the price for re-man's on this car?

Thanks again,

------------------
William
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles
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  #5  
Old 08-04-2000, 12:56 AM
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Join Date: Apr 2000
Posts: 166
The brake fluid in my car was changed on schedule and according to MB procedures. My failure, at least, was not due to maintenance neglect.

Calipers are available from Performance Products and probably from PartsShop on this site. To give you some idea of cost, rear ATE calipers for the 123 model, not TD, (the only Performance Products Catalog I have) are $91.41 each. The seal kits for ATE are $15.05 each. There is no mention that these are rebuilt units and there is no core charge, so my guess is that they are new. I have no idea what remanufactured units may cost.

Good luck with your project.

------------------
Ted
1979 240D
160,000 miles
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  #6  
Old 08-04-2000, 08:05 AM
Larry Delor's Avatar
What, Me Worry?
 
Join Date: Jun 1999
Location: Sarasota, Fl.
Posts: 3,078
For that price, I'd have to guess that those calipers are rebuilt. (no, I am not going to bet $5 bucks on that! )

-Larry
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  #7  
Old 08-04-2000, 09:17 AM
LarryBible
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I have rebuilt calipers on the 123 cars with great success. Because I'm the tight fisted, anally retentive person that I am, I would rebuild them rather than replace them every time, unless I found the bore or piston had a problem which would preclude rebuilding. It's really not that much trouble. If I were doing it professionally with the labor costs to consider, rather than only parts costs, that would be a different matter.

And yes, if the system was never flushed and bled, that's probably what killed them. The fluid absorbs moisture, and then the moisture does them in. When I'm evaluating a used car, it's always impressive to see that the brake fluid has been flushed regularly.

Good luck,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

[This message has been edited by LarryBible (edited 08-04-2000).]
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  #8  
Old 08-04-2000, 05:11 PM
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Join Date: Apr 2000
Posts: 166
This discussion has raised a question in my mind. Since the changing fluid maintenance had been done on my car, I concluded that changing the brake pads in other than the MB manual described manner must have been what caused my problem. I didn't have the special tool, just did my best to press the pistons back squarely without it. May not have succeeded.

Has anyone else had a similar experience and what other thoughts does anyone have about this?

Thanks for any observations and comments.

------------------
Ted
1979 240D
160,000 miles
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  #9  
Old 08-04-2000, 05:17 PM
LarryBible
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Ted,

Maybe I've just been lucky, but I've done brake pads probably a half dozen times on my 240D. I'd have to look in my logbook to know for sure. I've also put brake pads in a number of other vehicles belonging to myself. I've always used a set of jumbo channel locks, carefully, to push the piston(s) back. I've never experienced any problems like you describe.

Good luck,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #10  
Old 08-04-2000, 05:38 PM
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Join Date: Apr 2000
Posts: 166
Thanks for the response, Larry,

Your methodology is the same that I used. Perhaps the calipers were just like so many other things on my car that failed without any particular explanation.

P.S. If you have changed pads only a half dozen times in 523,000 miles, you have gotten about 87,000 miles use from each set. From the time my car was new, a set of front brake pads would only last about 30,000 miles and neither my wife nor I are aggressive drivers. Have you always used your car on a long commute? Thanks again.
------------------
Ted
1979 240D
160,000 miles

[This message has been edited by Ted2222 (edited 08-04-2000).]
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  #11  
Old 08-04-2000, 06:11 PM
WmHarlow
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Larry and Ted,

My father was a mechanic for 40+ years. I learned about cars from him.

Even though there was a special tool in the tool box for pressing caliper pistons, the 'jumbo channel-locks' have always been the tool of choice for easy compression. I too have never had problems arise from the use of channel locks for brake work. Between my father and I, we have been doing it for almost 70 years in total!

Three things my tool box will never be without... big channel locks, a big hammer, and a long screwdriver. If the 'special tools' do not work, one of these will.

Back to the main question, do I need to replace both rear calipers or can I get away with one for now and the other later? Would it be a good idea to replace all four? Sort of preventative maint. before the front ones fail. Could the previous owners lack of maintenance have damaged the master cylinder?
I have had this car for 5 years and only flushed the system three times myself, the last one was almost 2 years ago. I have learned my lesson, the brake system starts regular, anual flushing starting now!

Thanks again,

------------------
William
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles
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  #12  
Old 08-04-2000, 08:35 PM
Larry Delor's Avatar
What, Me Worry?
 
Join Date: Jun 1999
Location: Sarasota, Fl.
Posts: 3,078
You would want to replace both rear calipers at the same time. The new one could have different characteristics than the old one, and next thing you know your 240 is wanting to jerk to the side for a moment while the other caliper catches up.
(the only time I ever replaced just one caliper, was on a '76 Malibu with 148k miles, and I didn't expect it to last much longer...plus I was young and dumb (now I am no longer that young)).

-Larry
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  #13  
Old 08-05-2000, 12:07 AM
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Join Date: Apr 2000
Posts: 166
William,
My father was a mechanic, also. I began working on cars when I was in Junior High, nearly 60 years ago. It would be interesting to know how many of the people participating in this forum had fathers who were mechanics.

Larry (Delor) is right, of course. The calipers should be replaced in pairs. Whether you want to replace all four is a matter only you can decide. How long do you plan to keep the car? How much do you use it? Would a failure at some unforeseen time in the future likely cause you a lot of inconvenience? Etc.?

My guess would be that the master cylinder has sustained some damage from maintenance neglect. You may want to dismantle it, check it out and put a repair kit in it if you find it is not too bad. I had to rebuild mine(right after the car got out of its one year warranty ) and found it very easy to do. It has now lasted about 20 years without further trouble.

Good luck with whatever you decide.



------------------
Ted
1979 240D
160,000 miles
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  #14  
Old 08-05-2000, 12:35 AM
WmHarlow
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Thanks Ted and Larry,

Checking parts shop for the calipers now.

Interesting thought on our fathers, Ted... Makes you think.

I figured the master cylinder would need service, but you never know... I also should have known better than to ask about the replacement of just one side. I guess I should stop being so miserly, but I just spent out a small fortune on the wife's car and my Mustang's front end. My 240 deserves the best, and I'll make sure she gets it.

I'll be making the repairs this next week if I can get the parts by then. I'll let you all know if I run into any problems with the master cylinder rebuild.

Wish me luck, and thanks for the help.

------------------
William
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles
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  #15  
Old 08-06-2000, 12:50 AM
LarryBible
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Ted,

Yes, certainly at least 95% of my miles are road miles. What will accelerate wear of disk brakes drastically is driving with your foot touching the brake pedal. When disk brakes came along, some of the people who always drove automatics would be touching the brake pedal while driving, didn't hurt anything with drums, but with disks, keeping your foot on the pedal ever so slightly would kill them quick.

I doubt that this is your problem though. If you drive strictly in the city and drive hard, 30,000 miles might not be too bad. But someone else will have to confirm that.

Yes, my Father was/is a mechanic. He did car work for awhile then was in the Fork Truck business. He retired in '83 and is now 79 years old and still does a good bit of car work. He buys Hondas at the dealer auction, fixes them up and sells them. Still works in the heat and everything. He also has always been a real analyst and great troubleshooter.

William,

Ditto on the tools, but I have to add one, a BIG, Big hammer. I think you were talking about the big screwdriver for a prybar. I have a couple of those. I have a SnapOn screwdriver that's so big it looks like there probably isn't a screw anywhere that it would be small enough to fit. When you first said big screwdriver, my extra long SnapOn screwdriver came to mind. I found it on the road about fifteen years ago. What a find, a SnapOn screwdriver! It's probably about 3 feet long. I would never have bought one, but I've been surprised how handy it is sometimes.

Have a great day,

------------------
Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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