I need some help with this issue:

Our 1983 300SD (my dad's car) has developed a very severe shuddering in the brakes when they are applied hard/very firm, and a very noticable but less-severe shudder when slowing down at a normal rate. At first I thougt maybe the drivers side rear rotor was warped as the brake hose to it had been curled on installation by some previous mechanic, and thus I thought maybe that caliper dragged and heated up/warped the rotor from fluid not going through the hose properly... Another reason to think this was that the left rear wheel had a noticably higher temperature to it (it was quite hot) when you checked them after driving, probably 2-3x as warm as the passenger side wheel.

Since I thought it was the rear brakes, I recommended we replace the rear rotors/pads/hoses etc....so we did that, but the severe shuddering on slowing down remains, so I think it is the drivers side front rotor/wheel, but it could be something else, I am not sure. It Really shakes the car when you do a hard stop, its actually a little scary...but the car stops just fine. After changing out the rear brakes, the left wheel still gets warmer than the right, but not as warm/hot as it used to, I'd guess its about 30-40% cooler. And the brakes appear to be working fine and the calipers on both sides moved smoothly and so on, so I really have no idea.

What could cause such a horrid shudder like that? He's thinking of just letting the dealership diagnose it, they've always been able to quickly figure out issues before, but they're expensive and we'd rather spend the $$ on parts/repairs on our own than on their "diagnosing".

Any ideas? Aside from my front left rotor warped theory (the vibration is way worse on the drivers side of the car, and it shakes the steering wheel too) I really have no idea what it could be. The car is smooth as silk when driving, the shudder only appears when using the brakes.

Hopefully someone can help...

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a warped rotor is the most common cause. but you would feel the pedal pulsing. I've had this problem several times on my SD and every one always points to the rotor and tells me that is the problem... but both times it has been the front suspension.

there is an easy way to check it.
jack up the front of the car. take off the front wheels. screw in one of the lug bolts. have someone sit in the car and hold down the break. then use a breaker bar to try and tighten the bolt. if the bolt is all the way tight you will see the whole steering knuckle move. look for the source of the movement.
on my car it was the arm that connects the lower control arm to the sub-frame. and the second time it was that same arm but where is connects to the lower control arm.

if your car is anything like mine then shake all the suspension components and look for rips in the ball joint seals... it is good maintenance. those parts go bad and you won't feel it in the drivers seat til is about to break.

if you have a bad bearing you will see the rotor assembly move and not the steering knuckle.

it could be your rotors... but the suspension can make a very bad shudder and you feel it most of the time when breaking due to the fact that more force is going through that part of the suspension.

Hope this helps

Nik

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While you're in there, and just for good measure, I'd check the brake reaction bushings as well... These could certainly account for some serious clunking and other noise - though I don't think you'd feel a shudder, per se.

So far, sounds to me like one of your calipers has a frozen piston. This would definitely cause a serious shudder, progressively worsening as the one pad on the working side wore down further...

Would be curious to know your resolution. Lou

You may find this interesting:

The '87 was sitting around doing basically nothing for six months. Finally got off my ass and started sorting it out. The test drives definitely exhibited the same shuddering that you describe.

Hmmmm.......interesting. Why should a shudder develop with the vehicle just sitting in the driveway?

I conclude that it can't be anything concerning the front suspension and I'm betting that the rotors are contaminated with corrosion.

So, I take it out and really beat the hell out of the brakes. Five or six panic stops from 50 mph. Dragged the vehicle down with power applied. I could "smell" the brake pads when I got done.

.......Problem resolved....

The SD is doing a similar thing........but to a lesser degree. It's developed slowly but is the daily driver. I hardly use the brakes for most of my travels..........so..........I may try some smoking of those pads and rotors and see how it goes.

There is a school of thought that states that there is no such thing as a "warped" brake disc. It's always contamination of the surface that most drivers conclude is "warpage" and they replace the disc. The problem goes away, because of the new disc, and they conclude that they were correct in their diagnosis.

Warped rotors are the likely cause of the shudder. Many people turn the rotors on German cars like MB and BMW but they are designed to wear with the pads and only used once. They give much high braking power but the rotors really need to be replaced when the pads changed.

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The rotors on the car are only about 2 years old, they are OEM MB pads and Brembo rotors, we repacked the bearings at the same time ourselves (my dad did it, and did it very very well). It has new front shocks and bushings and the sway bar and bushings are all new as of 8 months ago (search: Sway bar epic ) so its very unlikely a suspension problem, especially since in all driving conditions and varying degrees of "fun driving" it handles tight and smooth and no shudder it glides down the road like a dream.....only shudders when using the brakes.

Brian, we'll go out this afternoon and try the "fry the pads" method and see if it improves anything....if it doesn't we'll probably just redo the brakes again, this time with better rotors. (Maybe the fancy crossdrilled ones )

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Concerning the last part, bull****. I have turned many rotors at napa an the bad ones just screeee quiet screeee quiet screeee quiet screeee quiet
screeee quiet screeee quiet screeee quiet screeee quiet, to claim that this is just 'contamination' is ludicris. Sorry i guess i flamed u a bit there,

You clearly don't understand the nature of "contamination". The brake pad material builds up unevenly on the brake disc and the result is exactly what you've described.

After you turn the rotor, the problem is resolved and you think you've fixed a "warped" brake disc.

It's possible that the disc is warped, but, minds a lot sharper than mine who live in this industry suggest otherwise.