knock, knock!

[Bitemylip]

Hey guys,

Was just wondering what part is bad when the engine knocks only when accelerating / pulling the throttle cable

theres no sign of the knock while idling.

On cold start, it also seems to make a weird rattle / unbalanced type noise for a second or two, then again idles fine.

Any help will be appreciated, i will try and get a recording of the sound when i get home.


Thanks
Simone

[pjdm1980]

Maybe a timing chain, harmonic balancer, bottom end could be a few things.

[hako]

Sounds like an exhaust manifold gasket leaking or a cracked exhaust manifold to me. The noise will be most apparent when accelerating whilst barely discernable at idle.

[Zuicider]

harmonic balancer is there any cracks in the rubber?

[TUF UTE]

failing injector or harmonic balancer

[Bitemylip]

i've uploaded a vid to youtube

YouTube - buick 3800 knock / rattle

Had a muck around with the car this arvo.

Seems to only make this noise when in park or neutral. I put the car in drive, with hand brake, and brake on, pulled throttle and engine made no noise...

Also had a look at harmonic balancer, looks too be intact and good condition.

[hako]

The rattle in the audio seems about half engine speed and definitely metallic....try removing the serpentine belt just to make sure it's not one of the pulleys - run it for no more than 10 seconds. If the noise is still there with the belt removed try to wobble the harmonic balancer side to side (engine off)...any movement will point to a buggered harmonic balancer. If none of these then it may be getting expensive but keep your fingers crossed. Any other symptoms or has any work been carried out on the engine in the last 3 months?

[Bitemylip]

just removed belt, still happens with it off - that sucks!

harmonic balancer seems to have no play at all.

It has had a new alternator put on, but other than that, i'm not sure, as i've just recently bought it.

Is it at all weird that it only happens in neutral & park??

[vt s]

hope its not pre-detonating

[H1GHROLLR]

time for a rebuild buddy

[gsxrdan]

harmonic balancer - mine is rooted too, noise is almost gone while driving, but pull up and idle and she sounds like bottom end bearing are gone; but then i see a great hunk of rubber hanging off the harmonic balancer and seems pretty obvious we found the problem!