Some opinions on a knocking sound

[havavb]

So guys my girlfriends mums VT has just hit the big 300,000k's car has never really had any problems apart from the usual wear and tear on parts. The engine seems to have developed a type of knocking sound on idle. Now the sound comes and goes randomly, it only knocks on idle, once you apply throttle it goes away. To me it sounds like its coming from the Harmonic Balancer, or maybe even a bearing in the motor? I could feel the knock through the foot rest in the car at one point. Car is a VT V6. Does anyone have some idea's on what it could be? Or had a similar scenario? Cheers. The noise sounds like a rotted spigot on a manual before the clutch is pressed in (only louder) That's as best as I could describe it. Currently she doesn't have the money to take it to a mechanic to have it looked it. So hoping for some assistance

 

[dirty hands]

knock felt under the foot rest ? ..engine at idle ..louder than a bad spigot bearing .. but is a knock random and goes away
300,000 km .
you mention a clutch type noise .. is it an auto

oil pump can knock can knock like that
if the harmonic balancer was in a bad way you expect something .... it can go out of balance
are the engine and gearbox mounts ok

a a rear engine bearing would knock all the time... wouldnt it

 

[havavb]

The car is an auto, is there anyway to tell the condition of the harmonic balanced without having it removed? All the mounts seem fine no signs of sagging, I was told (and u quote) "a tooth may have broken off of the harmonic balancer". I don't know if this is true, but would help explain the problem I guess. The sound does sound like it's coming from the front (why I speculate the harmonic balancer) I did try tightening it the noise seemed to have dimmed down but went back to how it sounded not long after

 

[johnny420]

has the oil level gone low?

have you checked the engine and transmission levels?

 

[Tree cutter]

Check the belt tensioner pulleys and idler pulley bearings.

 

[havavb]

I'll check the oil level tomorrow, to check the pulley bearings would I have to pull the pulleys off? Or can I check them on the motor? Thanks for the quick responses guys

 

[hotrod]

sound like you need to get it checked out by a mechanic , idle pulley bearing wont be it if you feeling it in the floor.

for your peace of mind get a vehicle report done (like u no same as RWC)

correct me if im wrong, if your harmonica was the problem wouldn't that upset the crank angle sensor.

sounds to me more like your engine mounts if its never been done with that many k's on the clock.

as well, like dirty hands said , oil pump that's close to were the noise is .

 

[dirty hands]

in this link it has a vidieo of a failing harmonic balance noise (sorry its not a VT )

--- How To Replace A Commodore Harmonic Balancer

"a tooth may have broken off of the harmonic balancer.....no tooth on a harmonic balancer

the motor has a timing chain that can go slack .and have a knock

 

[monkey]

Hotrod is correct the harmonica will upset everything within earshot

 

[hotrod]

if you starting to feel noise in the floor you should be looking at this main areas :
# engine mounts x3
# tail shaft centre bearing
# uni joints
# front bushers
# extension housing bearing .

That's why you need to get a full check over , the noise your hearing from the engine will not travel in to your floor.
can be any number of things like:
# timing chain
# lifters
# oil pump
# and it goes on .