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#1
03-27-2013, 07:31 AM
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Rust Spots Rear Rotors: Necessarily Indicative of a Problem?
Yesterday I had the snows removed and the regular tires put on....92 300D. The tech made the comment that it didn't look like the rear calipers were engaging because of rust SPOTS on the surface of both rear rotors (the spots are evenly distributed over the surface, but there's still plenty of bare metal to be seen). This is a car driven every day so I was surprised to see the spots. And on my 91 300D (same driving patterns....if anything driven less) the rotor surfaces were perfectly clean. So I'm thinking I might be needing new calipers.
As it's due for a state inspection, I set an appointment (different shop). I mentioned the brake issue and the tech that rust spots on the rear are not necessarily indicative of a problem. What are anyone's thoughts?
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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles 06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife Last edited by shertex; 03-27-2013 at 08:45 AM. 
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#2
03-27-2013, 07:44 AM
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could be leftover damage from PO driving with the rivets grinding on the rotor...
got pics?
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!!  1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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#3
03-27-2013, 08:25 AM
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Quote:
No pics....son gone for day with car. Maybe I can take some later.
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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles 06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife
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#4
03-27-2013, 08:42 AM
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pics would help sure.
My 190E's rotors would rust up a bit after a rain and me not driving for a day or two. They would clear up after some driving though. Miles down the road I replaced the rotors with some R1 Concepts units that have zero rust even after sitting all winter.
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Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out. Check here for compatibility, diagnostics, and availability! (4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!) 82 300SD 145k 89 420SEL 210k 89 560SEL 118k 90 300SE 262k RIP 5/25/2010 90 560SEL 154k 91 300D 2.5 Turbo. 241k 93 190E 3.0 235k 93 300E 195k
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#5
03-27-2013, 05:11 PM
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Here's a pic:
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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles 06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife
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#6
03-27-2013, 05:58 PM
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One thing to notice in the pic: there's an inner band with no rust. So it looks like the pad is making contact there but not on the rest of the rotor?
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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles 06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife
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#7
03-28-2013, 08:32 AM
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Hmm I'd pop the wheel off and take a look at the pad itself. Kinda odd only one area of the pad to contact the rotor.
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out. Check here for compatibility, diagnostics, and availability! (4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!) 82 300SD 145k 89 420SEL 210k 89 560SEL 118k 90 300SE 262k RIP 5/25/2010 90 560SEL 154k 91 300D 2.5 Turbo. 241k 93 190E 3.0 235k 93 300E 195k
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#8
03-28-2013, 09:15 AM
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Agreed, I would think that rotor would be polished shiny.
I think you have poor pad-to-rotor contact at that wheel. Brake hose restriction??
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The OM 642/722.9 powered family Still going strong 2014 ML350 Bluetec (wife's DD) 2013 E350 Bluetec (my DD) both my kids cars went to junkyard in 2023 2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles) 2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles) 1998 E300DT sold to TimFreeh 1987 300TD sold to vstech
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#9
03-28-2013, 11:55 AM
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totally typical of a seized piston. time for replacement/rebuild...
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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#10
03-28-2013, 11:56 AM
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the reason it's touching in that one spot, is the caliper is TWISTING THE ROTOR each time you hit the brakes hard... because only the opposite piston is making contact.
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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#11
03-28-2013, 11:56 AM
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I would also recommend replacing the brake hoses while you're down there, especially if they've not been done before and they are 20+ years old...
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out. Check here for compatibility, diagnostics, and availability! (4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!) 82 300SD 145k 89 420SEL 210k 89 560SEL 118k 90 300SE 262k RIP 5/25/2010 90 560SEL 154k 91 300D 2.5 Turbo. 241k 93 190E 3.0 235k 93 300E 195k
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#12
03-28-2013, 01:54 PM
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Thanks, guys....after 21 years and a car I plan to keep forever, new calipers and hoses (and pads and rotors) seems like a no-brainer.
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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles 06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife
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#13
03-28-2013, 02:01 PM
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Actually you could put some stainless steel lines on in place of those rubber ones! They're not too pricey either!
I've got these on my 300D and the brakes are most excellent! WRXtra WRXtra
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out. Check here for compatibility, diagnostics, and availability! (4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!) 82 300SD 145k 89 420SEL 210k 89 560SEL 118k 90 300SE 262k RIP 5/25/2010 90 560SEL 154k 91 300D 2.5 Turbo. 241k 93 190E 3.0 235k 93 300E 195k
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#14
03-28-2013, 02:57 PM
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I just recently experienced similar on my 190 on a rear. Was my first time into MB brakes. Thought it was really strange that only the outside pad was worn until I removed the caliper and realized there was a piston on both sides unlike the typical car with a single piston. Was definatley over-engineering as the pads themselves were tiny.
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You can't always get what you want, but if you try sometime you just might find you get what you need.
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#15
03-28-2013, 05:00 PM
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How has the car felt under different braking applications? That should Have been something you could discern, unless the car has been stopping strangely for a long time, and you just didn't notice it.
Time for a rebuild. Sumpthin's not makin contact right.......
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