Thursday arvo, I was heading to rocky with the wife and after overtaking a truck and hitting around 120kph (didn’t rev it much) and backing off the throttle heard a tinny ‘knock knock knock’ sound coming from the front end of the car. It stopped after about 3 or 4 knocks. I stopped the car and had a look under the car and bonnet before heading on our way again. A few Km’s down the road I eased the throttle on to overtake another truck maxing my speed at about 115 this time and again as I backed off the throttle the knocking sound returned, only this time it didn’t disappear.

I’ve attached a video file that captures the sound pretty well and am wondering if you can give me your thoughts.

8 friends who are fitters and mechanics have looked and listened and so far I’ve been told everything from bearings, to rods, and rockers. The car runs fine, except for the noise from the motor, I know this as I had to drive it about 10 k's back to a roadhouse so it didn't tay stranded by the side of the highway, it doesn’t sound like its missing, and the exhaust smells fine, there is no water in the oil either.

The only hints I can give you is that when we put a screwdriver on the block you can’t hear the noise (through the screwdriver), when you put the screw driver on the head you can hear the tinny knock really amplified. It also seems as though the sound is coming from the front half of the motor.

Any help you can give me would be great.

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Edited 13/12/09 07:36 AM13/12/09 07:36 AM by mattyb

sounds like an exhuast manifold leek

Edited 13/12/09 07:43 AM13/12/09 07:43 AM by baf6

sounds a lot like neos engine. we were convinced it was coming from the front of the head but it turned out to be 3 bent rods :(

sounds like your missing a bolt out your exhuast manifold or turbo housing - well that is what mine sounds like when the bolt falls out the turbo once every 6 months

matt,

when we unloaded the car off my trailer at your house I stuck my hand down the Lh side of the block whilst running. about 3" back from the oil filter I could feel where the knock is coming from. I would say it has bent #3 or #4 rod and is just tapping the block, you may be lucky and get away with just a set of "BIG ASS RODS" and brgs so long as it hasnt fractured the block anywhere. OR a complete FG F6 short motor.

that's my thoughts anyway...

Larso:)

man it must be a very different sound in real life then on the video cos on the vid if definately sounds like an exhaust leak for your sake dude I hope gravelrash is wrong (no offence intended)

sounds like an exhuast manifold leek

nah definately not an exhaust leak, its not easy to pick up in the video but its a mechanical tap-tap-tap sound.

since when can you install sprinkler systems in our cars?!?!

sounds like a piston/rod to me ;( any white smoke or fluid leaks?

Dude.. That has gotta suck !!!! At least you haven't pt a leg out of bed like I did... It will be alot cheaper for you to rebuild it without repacing cranks sumps starter motors etc...... I now have a spare engine just in case that it happens again.... Good luck and keep us posted...

the sound in the video is 99% the same as in real life. I'm doing a compression test tomorrow. that'll tell if it's a rod.