sl55per

03' SL55 w/29K. She usually sits on a trickle charger during the week

Recently started making an odd sound BEFORE startup. After I get into the car and press on the brake pedal this noise is coming from the engine bay [VIDEO] - https://www.dropbox.com/s/09j1o3z5ep...artup.mp4?dl=0

This noise is happening before I even push the Start button on the shifter. Any thoughts? I have not yet been able to determine if this happens before every startup or only after the ones where it's sitting a while.

Dave3359

Mine does that to I believe it's the SBC unit powering up the brakes. But I'm sure someone else can confirm this

moretech

Mine does that too, a sort of --brrrrrr (rumble) sort of noise. For mine it is the SBC pump. I am pretty certain that is it.

moretech

sl55per

Interesting, it just seems so incredibly loud to be normal. It hasn't seemed to affect driveability any and I am not finding any kind of leaks under the hood.

I just noticed something else interesting, after I took her out for a spirited run I pulled into the garage and after I shut the car off the same (Brrrrrrrr) noise came back. So I can verify BEFORE startup and AFTER turning ignition off. Now I need to determine if this is every time or only after she is sitting for a while.

So the consensus so far is that this is normal? I suppose the supercharger pulley squeak is considered normal too so why not right? (dielectrics grease did fix that)

Rudeney

Normal. It's the SBC's electric pump pressurizing the system. Mine does it sometime just when opening the door with the engine off. Anytime it registers the pressure below a certain level, the pump will run. It does "go to sleep" after sitting a while, but then anything that sends a CAN bus wakeup signal (unlocking, opening a door, etc.) can cause it to run if it needs to pressurize.

crehop

Yup its normal, nothing to be worried about, mine does it too. this car has a few sounds that seem abnormal but are normal, after a while you will get a feel for it.