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  #16  
Old 07-14-2002, 01:56 AM
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Nothing really is visible until you get the assembly taken apart and try pushing back the caliper piston. And then having someone lightly push the brakes and watch its action.

I'd say it is a problem most often diagnosed by the symptoms. And if the mechanic doesn't associate pulling and shaking with a stuck piston against warped rotors, they're just going to replace what they can SEE is bad.

You probably have to explain all the symptoms and also what has been done to the car so far. Then emphasize the heat, shaking and pulling to one side and tell them they need to thoroughly check the brake calipers.

Disc brakes are great when they are working like they are supposed to, but nobody seems to have found a sure-fire way to prevent stuck caliper pistons. It can happen due to light corrosion, improper manufacture, overextention and then twisting, and foreign object.

Relatively easy to test though when the brake assembly is taken apart and the mechanic takes the time to test the action of the caliper.

Ken300D
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  #17  
Old 07-14-2002, 02:54 AM
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767Flyer,

If you want to find out if the caliper is causing the pads to drag, just jack the car up to get the wheel off the ground and try turning it. You can easily feel and perhaps hear a "dragging" sound.

This happened to my car once while on a long trip. The car started pulling very very badly to the right. When I stopped, I jacked the car up and found the right front wheel very hard to turn. I had found the problem!

Hope this helps. Let us know what you find.
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  #18  
Old 07-14-2002, 03:39 AM
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Thanks Ted and Ken - I do appreciate it! I will jack the car up tomorrow and test 'er out. Why is it that some of the simplest causes have escaped my brain with this car? I guess I have been so wrapped up in the high-tech stuff with it that I have failed to see some basic car stuff going on.

Thanks again!

Mark E.
Ft. Lauderdale
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  #19  
Old 07-14-2002, 12:17 PM
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On a normally functioning brake, you will hear a dragging sound, as the brakes do rub very lightly.

When you spin the tire, it will not go on spinning forever, as long as it turns relatively freely, it should be ok. Usually getting 2-3 turns out of a wheel indicates that it is ok.

The true test that I like to do is to get out on the highway drive for 10 miles or so without using the brakes and pull into the next highway rest stop at the earliest convenience. When you are slowing down, do not use the brakes, engine brake the car all the way down to below 10 mph, then use brakes to stop. It is important that you carefully engine brake the car all the way down to a walking pace. Now, you have been on the highway without any brake use and you did not use the brakes to stop the car. All brakes should now be cold and all be the same temperature. If a brake was rubbing due to a stuck caliper, that rotor will be hot (just be careful not to burn yourself).

H rated tires are fine, they are good up to a speed of 130 MPH and the C class is governed at 133MPH, so I do not think there is any need to go to V rated tires.

Also, I did not mean to automatically condemn your tires. Continental does make good tires, I just suggested to possibility of wanting to purchase Michelin tires and for you to check your tires to make sure there are no flat spots. There is no need to keep spending money on the car, unless you really want Michelin tires.

-Good luck.
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  #20  
Old 07-14-2002, 01:03 PM
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Ali,

I like the diagnostic thought involved with your technique.

If you can get access to an infra red thermometer, you don't even have to go to such extremes. Last week I drove an old (1977) 450SL around the block and put it directly onto my drive-on lift. The Front right disc was320 degrees. The rear right was 280 and the other two were about 150. We rebuilt all four calipers.
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  #21  
Old 07-14-2002, 05:57 PM
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Steve,

Actually, I do have an infrared thermometer that I keep in my car and I do use it to check various parameters on the car. When I do this test on my car with the thermometer every brake disc is almost exactly ambient temperature.

I initially got the thermometer because I thought it would have a few uses on the car. Now, there seems to be countless uses for it. For me, I think it was money well spent.

A couple of years ago, on my 325e bimmer, following a brake pad change, the caliper was rubbing so hard that after 1 mile of driving I could smell the brake burning smell from inside the car. Needless to say, the car pulled very heavily, and all was well after a caliper replacement.
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  #22  
Old 07-14-2002, 07:34 PM
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Ali - I will try it out. now I have a dumb question - could a bad tire(s) cause a car to go out of alignment? Shaking I understand, but could enough wobble pull the alignment out? Just trying to eliminate stuff before I trek back to the shop. Also, you recommend rebuilt calipers instead of new ones? Do they last as long? I'm tired of the car being in the shop more than I drive it! :p

Thanks!

767Flyer
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  #23  
Old 07-14-2002, 07:51 PM
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sounds like brakes, get on the highway cruise for a couple of miles, stay off brakes, then coast to the side shoulder, stop with emergency brake at around 10mph or less, then feel wheels.

What is your brake fluid change schedule since new? every two years?
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  #24  
Old 07-14-2002, 08:06 PM
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767Flyer,

The vibration you have described should have no effect on alignment, however, a badly wearing tire due to unbalance or other vibration could affect the straight line performance of the car. Overall, I suspect you have a sticking caliper and I would address that as the most likely cause/ possiblility. Other, at this point seemingly less probable sources of the problem can be checked once this one has been definitively eliminated. Jim
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  #25  
Old 07-14-2002, 10:56 PM
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OK guys thanks - I will run a few "tests" and check it out. I do recall my mechanic telling me there was excess wear on the front tires (new, about 2000 miles on them and freshly rotated), which I thought was strange considering my driving habits.

I will let you guys know.

Cheers,

Mark E.
767Flyer
Ft. Lauderdale
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  #26  
Old 07-16-2002, 07:58 AM
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Well, I did the drive 10 miles, no brakes, coast to a stop test. The brakes were completely cool. Nothing! So I guess no stuck caliper. So it is sounding more like tires. In fact, each day the shaking gets worse and worse, and gas milage is starting to suck big time. One last question - what else in the suspension, if anything could be a culprit? When you have new rotors/brakes put on, is it customary to check the wheel bearings? How about shocks?

Thanks,

Mark E.
Ft. Lauderdale
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  #27  
Old 07-16-2002, 09:13 AM
iga
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I still wouldn't dismiss a binding brake on the basis of the 'coast to a stop' test. It could only start binding after a firm application or some heat has built up. I would also consider the flexible brake hose, even if it appears sound from the outside. My brother replaced a front caliper twice on his Alfa Romeo before realising that the flexible hose had collapsed internally - you could push brake fluid through it but it wouldn't let it return. Best of luck tracking down this problem!
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  #28  
Old 07-16-2002, 11:04 AM
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Were you shaking and pulling to the right during this 10-mile drive?

Ken300D
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  #29  
Old 07-16-2002, 12:23 PM
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Well everyone - do I feel like a schmuck. Today I finally said what the hell - I went and bought some Michelins. Guess what? Problem solved. After all I've put you poor guys through Geesh. Sorry! Anyway, I learned a lesson here. I'm just really surprised that tires with only 10k on them would give me fits. And I just bought Continentals for my other C280 - and the ride sucks on it too. I was amazed at the ride; smooth as silk, no bone jarring over bumps, and the car is responsive again. Wow. Anyway, thanks for all your help, I do appreciate it! I should have listened to the masters: Steve, et. al thanks.

Phew - I feel better now - the car feels like a benz again.

Mark E.
Ft. Lauderdale
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  #30  
Old 07-16-2002, 12:56 PM
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Excellent! Many of us have learned from your experience.

I'm staying with Michelin for sure. It seems that news story about a majority of current tires would fail more rigid standards has a lot of truth in it.

Firestones have been bad since the 70s - never understood why people kept buying those.....

Ken300D
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