mlandis

Hi, folks, first thread....

I just bought my 2007 SL550 recently, but this didn't start happening until two days ago. When starting up the car in the morning, I hear a ratcheting noise -- kinda like fishing line being reeled out at high speed -- that goes on for about two seconds, then stops. From the driver seat, the noise sounds like it is coming from dead-center of the hood, near the top of the engine compartment. (It stops before I can hop out and check.)

Now, once it happened when I started the car, but once it happened before I even had the opportunity, so it may have been coincidence. (I have Keyless Go, so presumably the car was waking up before I started it.) This occurred when the outside temperature was around 47 F. It hasn't occurred when I've been at work, where I am in an underground garage that is pretty warm, so I am guessing this is a temperature-related thing, but haven't seen any similar-sounding posts here, so don't know if it is expected.

I'm guessing it is a stepper motor somewhere, but that is a total guess. Any help or direction would be appreciated.

Bam Bam

That noise is probally coming from your starter. With other cars sometimes you hear a noise like that followed by the rumble of the engine.
Maybe poor electrical signals between your starter and sparkplugs. Iam guessing check your sparkplugs and sparkplugs wire?

dan1495

Don't know if it is the same thing, but my SL55 make a similar noise. On one occasion it never stopped until I disconnected the secondary battery which turned out be a relay issue. In my case the noise is coming from the secondary air injection pump, and now that I know what it is I can hear it when I first start the car in the morning. Cuts off after a few seconds normally. Something to do with the emission system.

Bam Bam

Milandis, have you ever tried to start a car with a bad or broken starter? Is the noise similar to the noise you are getting from your car?

mlandis

No -- and it happened even before I switched the ignition, so I doubt it's the starter. It's not a loud clicking noise, more like a stepper motor. This morning the outside temperature was 57 F and the noise didn't happen.

mlandis

Can you hear it consistently, as in every morning? Or only in certain temperature ranges?

dan1495

I only hear it at initial startup in the morning, and it is more noticeable when it is colder.

ToonArmy

Is this on startup, or before? Wondering if you are hearing the SBC pre-load. As I understand it, when you open the door (I don't have keyless go), the system pumps up the pressure in the SBC system to be ready to go. I'd describe the sound as a bit like a ratchet, or a short burst of garage door (but softer).

mlandis

Bingo! ToonArmy wins. When I googled "SBC pump" I found a link at benzworld where somebody posted a clip of what it sounds like on an E-Class:

http://www.benzworld.org/forums/w211...ml#post3207374

This is almost identical to what I am hearing, albeit for a shorter period. Thanks for the tip!

Rook3300

Interesting, I think I've heard this once from my SL but I just ignored it as one of the many pumps that activate before the "spaceship" launches. There are so many sounds that occur when priming/starting this car, it's almost hard to keep track.

Oh man, believe me when I say that a starter motor has a very distinct sound that can't be mistaken for anything else. I'm sure everyone would agree. And I just love it when they put one of the bolts directly on top of the unit just below the transmission casing. Knuckle-busting fun!

Rook

mlandis

LOL -- glad to hear I'm not the only one that refers to my car as a spaceship. It's not really a car, is it?