Series 2 V6 engine noise

[mischf]

Good evening sirs,

I have purchased recently a 91 VN Commodore (V6) and all is well except for a rapid knocking sound that seems to come from the bell housing area. It is consistent with the speed of the engine ie: faster revs = faster knocking but the sound level remains the same. It sounds almost like a machine gun but on a lesser scale and is much more noticeable inside the cabin. Thank you for any input.

[frogslapper]

Just a quick reply. It is very common on vns for the front harmonic balancer to fail.This will sound like a death rattle in the engine.Check the balancer closly to make sure the inner rubber has not cracked or distorted.

[mischf]

Hi frog,

I am aware of the fault with the harmonic balancer. The sound seems to come from the rear of the engine, could it be the torque converter?

[BrianT]

my vp has a big end bearing knock when it warms up .At idle and just above idle you can hear it...After 600000 plis ks i aint complaining

[mischf]

It's only done 209,000kms. The sound is always there but you can't really hear it over road noise, just when it's idling.

[CSL]

that would be the flywheel. when you rev it up it spins into line thanks to the forces of rotational gravity. mine cracked a gooden, i got another one for $40 bucks, but really thats one thing you dont want coming off at a few thosuand rpm cause it will slice and dice. for the record it's an 8 bolt flywheel and it should have like a spacer tack welded on (bout .6 - 1 mm spacer)
Is your car getting harder to start???
look mine got progresivly worse until it was clackin like an old man with torly full of tin cans.easiest way to do it is to
unbolt dirft sahft from diff yolk (4 bolts) unbolt centre bearing, and slide tail shaft out of auto (warning: there wil be oil flowing out bring a bucket)
then unbolt auto from engine, and making sure it nice and supported on a trolly jack, take off the cross member (tranny Xmember). now as you slide the auto out you'll find the torque converter staying on the auto. It is botled onto the lywhell with 3 bolts, you need a mate on the balancer to crank the engine around so you can get to all 3 bolts. the it's just a matter of taking off the 8 bolts holding the flywhell onto the crankshaft. oh also you need to take off the starter motor, mbaye your y peice of the zorst, and the inspectin plate.
if yur stil not sure, just take off the inspectino plate and have alook, and see if you can jiggle the flywheel about.
when i took mine off my mate tapped it with a hammer and the centre fell out, ever so close to cutting my car in half

[mischf]

not good.

any other suggestions anyone??

[Fu Manchu]

This noise happens in mine as well. I have had everything checked over and no one has found the bizo in the bell housing to be faulty.

If I depress the brake peddle hard with no shoes on I can feel the knock pulse through the peddle.

If I hold the fuel pipes on the fire wall I feel this very strong. It has been suggested to me that fuel pipes maybe touching the body somewhere as this is directly in pulse with how the injectors operate.

I am thinking there may be a rock jambed inbetween the lines and the body. Haven't checked yet but it would explain why I feel it through the brake as those lines run with the fuel. It could be a damaged rubber grommet in there as well. From the engine bay the pipes don't touch anywhere.

Apparently the is also a holden part ( a damper, I have the part number somewhere) that is fitted to the return line that stops this)

I seems loudest behind the front right from the inside and can only just be heard in the same area with ya head under the bonnet.

The engine has 20000 and the gear box about 30000