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beeda
05-03-2011, 10:28 PM
I'm getting a weird rumbling harmonic from the engine bay/back. Any ideas? Could it be heat shielding on exhaust?
DarkPhoenix
05-04-2011, 10:17 AM
I'm getting a weird rumbling harmonic from the engine bay/back. Any ideas? Could it be heat shielding on exhaust?

Is that in gear or out of gear?
beeda
05-04-2011, 10:23 AM
Both
DarkPhoenix
05-04-2011, 10:33 AM
Check the crank pulley and also check the driveshaft. There could be some play in either that could cause that. Does it do it while just idling?
beeda
05-04-2011, 11:17 AM
Ok I will. No it doesn't during idle. I'll check those today, maybe its finally time for a lw crank pulley!
DarkPhoenix
05-04-2011, 11:22 AM
Ok I will. No it doesn't during idle. I'll check those today, maybe its finally time for a lw crank pulley!

When you have the car running, rev it up to 3k and keep an eye on the pulley. If it doesn't show the same symptoms, then it is somewhere in the driveline. Let us know what you find out.
mike-tracy
05-04-2011, 02:14 PM
A lightweight pulley typically "deletes" the rubberized "dampener" in the stock pulley. So as DP above mentioned, watch it while you rev up the engine, and if it's not spinning smoothly, either the crank bolt is loose, the pulley is genuinely damaged, or you have crank walk. I've had all 3 in different subie motors over the years. A light weight pulley is a decent upgrade, but light weight wheels (such as RS 5 or 6 spokes, or STI BBS, etc) will be a bigger upgrade.
DarkPhoenix
05-04-2011, 02:32 PM
A lightweight pulley typically "deletes" the rubberized "dampener" in the stock pulley. So as DP above mentioned, watch it while you rev up the engine, and if it's not spinning smoothly, either the crank bolt is loose, the pulley is genuinely damaged, or you have crank walk. I've had all 3 in different subie motors over the years. A light weight pulley is a decent upgrade, but light weight wheels (such as RS 5 or 6 spokes, or STI BBS, etc) will be a bigger upgrade.

Never seen any Scooby engines crankwalk, but I did have two 4G63s walk on me which sucked!!

The other thing to look for, that happened to me, was the crank sprocket and keyway getting munched by it moving. That will kill the crank pulley too.
Grafton
05-06-2011, 11:43 AM
A lightweight pulley typically "deletes" the rubberized "dampener" in the stock pulley. So as DP above mentioned, watch it while you rev up the engine, and if it's not spinning smoothly, either the crank bolt is loose, the pulley is genuinely damaged, or you have crank walk. I've had all 3 in different subie motors over the years. A light weight pulley is a decent upgrade, but light weight wheels (such as RS 5 or 6 spokes, or STI BBS, etc) will be a bigger upgrade.

Never seen any Scooby engines crankwalk, but I did have two 4G63s walk on me which sucked!!

The other thing to look for, that happened to me, was the crank sprocket and keyway getting munched by it moving. That will kill the crank pulley too.

the phase 1 engines are more likely to do it, my brother-in-law's 200k+ 1.8L impreza had it pretty bad