Anyone have any diagnostic suggestions for my ’86 560SL?

Recently, my car has started to make a “creaking” noise. The sound appears when, from a stationary position (i.e., at a stop light), you remove your foot from the brake and start to roll forward. The sound disappears once the accelerator pedal is applied and the car accelerates.

To my ears, the sound seems to be emanating from the front suspension, but I’ve no better guess as to the cause.

Any ideas?
Thanks for any suggestions!
Ryan Potts

Ryan,

Diagnostic suggestions:

How long does this continue if you don't put your foot on the gas? Try this in a nieghborhood or large parking lot.

Can you coast with your foot lightly on the brake and still hear it?

Does it happen in reverse gear?

If you let the car start coasting in Drive, then move it to Neutral, does it still groan?

Does it happen if you are turning left or right?

Try releasing, setting, and releasing your parking brake to make sure it's not sticking. Try using your parking brake when you are coasting slowly.

__________________
NOW: 2017 C43 AMG, 2006 Wrangler Unlimited Rubicon, 1966 230SL, 1980 450SL (for sale!)
PAST: 2006 C230, 1997 E300D, 1994 E420, 1994 Neon Spt Cpe, 1984 300ZX, 1983 Celica GT, 1976 Electra Limited, 1984 Honda Nighthawk 650, 1979 Suzuki PE175, 1978 Suzuki DS100
www.mbca.org - www.sl113.org - www.ohio4x4.com

Hi Rodd - thanks for the reply. I've tried to answer your comments:

Diagnostic suggestions:

How long does this continue if you don't put your foot on the gas? Try this in a nieghborhood or large parking lot.

- the creaking noise stops as soon as I release my foot from the brake and the car starts to roll forward, so it isn't directly related to stepping on the gas, rather releasing the brakes and allowing the car to move forward

Can you coast with your foot lightly on the brake and still hear it?

- no, it only creaks when the car starts to move forward after being at a complete standstill

Does it happen in reverse gear?

- yep, same thing, just creaks when the brake is released and the car starts to move backward

If you let the car start coasting in Drive, then move it to Neutral, does it still groan?

- no

Does it happen if you are turning left or right?

- no

Try releasing, setting, and releasing your parking brake to make sure it's not sticking. Try using your parking brake when you are coasting slowly.

- parking brake doesn't make any difference, i.e., the car still creaks whether the parking brake is used whilst the car is stopped or not

Any ideas?
Thanks again, Ryan

For what its worth - my 'guess' is it is noise emanating from pad and disc. Maybe a bit of stiction which could be helped by a pad change (ru using MB pads I believe they are recommended by most) alternatively it could be a lazy piston or just general gunge around caliper sliding surfaces,

NormanB

__________________
NormanB
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K

i know what your talkin about. its your brakes.... it happens when you have your foot just slightly on the brakes too. i used to make my car sing. haha. same thing happened to me on my car. nothing to worry about. but check them and put some brake grease on them.

__________________
1989 260E
- 300E engine
1998 C230
1995 E320

Have you checked/replaced your rubber flexible brake lines recently? Worn and soft lines will resist pulling the pads away from the calipers when taking your foot off the brake pedal.

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

For what it's worth, i have got the same noise coming from my front end on my 84 sl. I suspected that it might me rubber bushings loading/unloading. But I will look into the sticking brake piston issue.

With the answers to your questions, I guess it to be the brake pads/disks as well. It sounds like the pads are not pulling away from the disk surface quick enough when the pedal is released. The previous posts seem to hit the points I would think of as well:

- rubber brake lines are swelled and constricted (common problem) and are not letting the fluid back out of the caliper.
- brake caliper pistons (or their rubber seals) are dirty or degraded and are making the piston stick in the cylinder.
- dirty/rusty pins that guide the brake pads are restricting movement.

If you're handy yourself, you could inexpensively replace the rubber brake lines, flush/refill the brake fluid, and examine the whole brake assembly (remove pads and caliper, examine the pins, piston seals, pads, disks, etc for anything unusual). Maybe it just needs a good cleaning. If you're not a DIY person, then you can have it done by your regular mechanic.

On my SL (a little older), I went about this "look and see" procedure and ended up replacing everything. New rotors, pads, rubber brake lines, rubber piston seals, and new pistons. I cleaned every associated part I could. Of course, I replaced the wheel bearings while they were accessible.

__________________
NOW: 2017 C43 AMG, 2006 Wrangler Unlimited Rubicon, 1966 230SL, 1980 450SL (for sale!)
PAST: 2006 C230, 1997 E300D, 1994 E420, 1994 Neon Spt Cpe, 1984 300ZX, 1983 Celica GT, 1976 Electra Limited, 1984 Honda Nighthawk 650, 1979 Suzuki PE175, 1978 Suzuki DS100
www.mbca.org - www.sl113.org - www.ohio4x4.com

Great - thanks everyone for the advice. Looks like I have another project to work on!

Ryan