Severe Shudder Through Car when Braking...help?! - PeachParts Mercedes-Benz Forum

pawoSD · #1 08-11-2006, 01:07 AM

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...

SirNik84 · #2 08-11-2006, 02:52 AM

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

DrLou · #3 08-13-2006, 09:15 AM

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

Brian Carlton · #4 08-13-2006, 10:02 AM

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.

Diesel Giant · #5 08-13-2006, 12:56 PM

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.

pawoSD · #6 08-13-2006, 02:52 PM

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

)

pawoSD · #7 08-13-2006, 10:24 PM

Well, we didn't do the pad burning event (he didn't want to), but we did take off a front wheel and checked the rotor with a dial gauge, it was quite warped on one side of the disc, and when "spinning" the rotor/disc hub it would spin freely around between the pads in the caliper, then catch on about a 20% area of the rotor and stop it from turning. Quite obviously the (very) warped spot. So we decided to just order some new parts: two crossdrilled super-rotors

, some PBR Organic Deluxe pads(great pads), two dust caps, and a couple wheel seals. The fun will begin when the parts are in.

They had darn well better last a loooong time once they're in. The stuff on there (brembo rotors and oem pads) barely made it two years. I had rear rotors warp on my car after 3 months though, and they were brembo too....from now on I am sticking to the higher end stuff, even if it costs a little more. Brembo were the cheapest at the time we bought them.

pawoSD · #8 08-18-2006, 01:04 AM

Well, the problem has been solved, it was the front brake rotors. We changed them out tonight with new Zimmerman Cross Drilled ones.

Coupled with a set of PBR Organic Plus pads it has some e-x-t-r-e-m-e braking power. We took it out and did some slow steady braking to work the pads in, then we tried out their power....he accidentally locked up the front wheels doing a hard stop!

Wow! Shudder is completely gone, they are smooth and extremely powerful. 7-8 heavy stops later, we were home and wow, we cooked those pads.

smelled burned.

So the problem has been solved. Hopefully it stays that way. Doing front brakes is not fun...

Wes Bender · #9 08-18-2006, 12:29 PM

Glad you got it fixed.

When you install wheels (or even after someone else installs your wheels), be sure and check the lug bolts with a torque wrench. Over-torqued lug bolts is probably the leading cause of warped rotors. 80 - 83 ft lbs is the usual spec.

I'm not sure that this was the case with yours, but felt that it needed to be said anyway.

Wes

pawoSD · #10 08-18-2006, 08:31 PM

Quote:

Originally Posted by Wes Bender

Glad you got it fixed.

When you install wheels (or even after someone else installs your wheels), be sure and check the lug bolts with a torque wrench. Over-torqued lug bolts is probably the leading cause of warped rotors. 80 - 83 ft lbs is the usual spec.

I'm not sure that this was the case with yours, but felt that it needed to be said anyway.

Wes

Yep I used a torque wrench to do every bolt I could, including lugs. Lugs I do to about 81lbs, the internal rotor hex bolts I did to about 111NM as per the MB service manual. Greased the bearings up nice and good too.

I am always very whiny about it at the tire place too, I go out there and make sure they torque wrench the lugs on by hand to 80lbs.

F18 · #11 08-18-2006, 09:36 PM

Quote:

Originally Posted by Wes Bender

Glad you got it fixed.

When you install wheels (or even after someone else installs your wheels), be sure and check the lug bolts with a torque wrench. Over-torqued lug bolts is probably the leading cause of warped rotors. 80 - 83 ft lbs is the usual spec.

I'm not sure that this was the case with yours, but felt that it needed to be said anyway.

Wes

Yes....I agree with Wes! Always hand torque the wheels on to the appropriate specs. If you have a new set of tires put on tell the mechanic that you want them "hand torqued" to X pounds.....don't let them air-wrench them on or they will warped your rotors.

pawoSD · #12 08-18-2006, 09:50 PM

Quote:

Originally Posted by F18

Yes....I agree with Wes! Always hand torque the wheels on to the appropriate specs. If you have a new set of tires put on tell the mechanic that you want them "hand torqued" to X pounds.....don't let them air-wrench them on or they will warped your rotors.

Yep, always have and always will. Discount tire is real good about it though, when I went in to have my tires rotated once I forgot to tell them to hand-torque them, but the guy mounting them did infact still use a hand torque wrench and my recepit said "All torqued to 80lbs" on it. I was very impressed.

donbryce · #13 09-01-2006, 10:14 AM

I was going to post a new thread, but this one addresses my exact same problem, a shuddering/vibration of the whole car when braking, much more noticable at high speed.
A bit of background: The car started doing this about a month ago, during a highway speed trip. Last year, during safety inspection, I was told that one of the pistons was sticking on the drivers side caliper. Since the brakes worked fine (at the time), I paid no real mind, thinking I'd do the caliper when the pads needed replacement. The car is stored indoors and unheated Nov - April, and sees little more than 4000 miles/year. (I paid special attention to Brian Carleton's post).
So, with the next inspection due this year (yesterday actually), I put a kit in the caliper and it now functions 100%. I also had a left over pair of new pads which I put in the rebuilt caliper (the pads on the passenger side front are still about 75%, and worn evenly on both sides).
I removed all calipers and checked the runout of the rotors with a dial indicator. The MB spec is .12 mm, or .0047 inches. I could not get a variation on any rotor over .002 - .003 inches. I measured at the outermost point on the fronts, just in from the ridge at the rim edge. The rears had a wider band of rust and scale outboard of the pad contact area, so the reading were taken a bit further in.
From the inspection, none of the ball joints in the front were loose or needing replacement, but I haven't tried the test recommended by SirNik84 yet. Will do that soon....but in the meantime, does anyone have anything to add to this perplexing issue???? ....Oh, I almost forgot, I also removed the 2 relays from the ABS black box temporarily to rule out that as a source. It makes no difference....

Rudolphrocks · #14 09-01-2006, 10:20 AM

Quote:

Originally Posted by Brian Carlton

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.

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,

Brian Carlton · #15 09-01-2006, 10:34 AM

Quote:

Originally Posted by Rudolphrocks

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.

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.