Vibration/rattle noise at low RPM

[klindstedt]

Having trouble finding the source of a noise at low RPMs. When the car is in gear (drive or reverse, makes no difference) and I'm stopped, the engine rpm is brought down below the normal idle of park or neutral. Somewhere just below 1000rpm I hear and feel a slight vibration and low frequency rattle or growl. Definitely RPM -dependent as the noise goes away when I rev up the engine. I've listened to the alternator, PS pump, water pump with my poor-boy stethoscope (piece of pipe) and hear nothing out of the ordinary from these suspects. Any one else ever encounter this and where should I be looking? Oh yeah, noise just cropped up around 5 days ago. Thanks!

[willwren]

Could it be metal/metal clatter? At idle primarily, but goes away if the rpm's are brought up slightly, especially power-braking in gear?

Look at the rubber face of the harmonic balancer. See if the rubber is starting to crack around the circumference. Your year/age is ripe for this (I've had this on both of mine already). As the rubber cracks with age, it allows metal to metal contact at idle between the inner and outer halves of the HB.

I'd say that's the first place to check.

[Skippy1827]

cat shield?

[klindstedt]

O.K., time for me to show my limited mechanical knowledge. Harmonic balancer - attached to the crank pulley, right? If so, how do I get access to see the rubber you're talking about?

At idle primarily, but goes away if the rpm's are brought up slightly, especially power-braking in gear?

Dead on. That's how I was simulating the noise for my dad to listen to see if he could hear it.

I lke the Cat shield suggestion as well. THAT I can check on my own...

[00Beast]

Harmonic Balancer is the crank pulley.

[klindstedt]

That said, where do I look to see this rubber face on the harmonic balancer? Looking at it from top-side, I only see steel...

[willwren]

Take the RF wheel off and remove the very-easy-to-remove fasteners on the inner fender liner. You'll be looking right at it.

From your symptoms, it's more likely than the cat heat shield, but that's easy to rule out as well.

[trf_ssei]

to check mine i put a socket on the alternator nut and slightly turned it back and fourth and watched the harmonic bolt. in my case the rubber had completly pulled away there fore the crank pully would move but the bolt would not until the metal on the inside made contact.

[Skippy1827]

so what was the rattle niose?

[klindstedt]

Sorry, haven't had time to look further. Got called out of town for a few days and have to fix the brakes on the wife's car when I return. I'll be looking for the noise again next week. I did have time enough to determine that it wasn't something simple like the cat shield...

If it is the harmonic balancer, am I doing damage or setting myself up for failure of the stranded variety by continuing to drive it?