ZD30DI Knock

[Paul I]

G'day,
Over the last few days, my 2004 ZD30DI Nav ST-R has developed a low frequency engine knock.
To me, it seems to be inside the engine, though I cant tell where.
It's low frequency, about every half second at idle, and doesn't vary through loading the motor up, so I suspect it's not Big End or Gudgeon.
At that frequency, it feels to me as if its on a belt, chain or something running slower than the crank.
Any ideas? I really don't want to pull the motor if I don't need to,
regards Paul

 

[Old.Tony]

At 700rpm (say), with 4 power strokes every 2 revolutions you should see about 9 power strokes every second. This is about 2 power strokes per cylinder every second - so it does sound like it might be relating to one of the cylinders. You could pop the glows and insert an inspection camera (if one fits, I've never done this), but you could also drop the oil and then the sump and look from underneath.

Quicker (and less time-expensive) - you could check the cooling fan, particularly the base of the blades, looking for cracks and excessive flex. If it flexes too much it will invite itself into the radiator for a wild fluoro-coloured party. Check also the shroud around the fan in case it's come loose, but gut feeling is something internal.

 

[Paul I]

G'day Tony,
Thanks for the reply.
It's definitely internal
regards Paul

 

[dattorob]

post a video with the sound.

 

[Paul I]

post a video with the sound.

Video's uploaded

 

[dattorob]

yeh your right. Does sound ancillary to engine though. Can you remove the fan belt just for a minute see if it still persists?

 

[tweak'e]

as above pop the belt off and test. idler bearings do fail, so does the damper and the actuator clutch. tho it typically sounds faster noise.
if it still makes it, put a pipe/rod on the engine and use it like a stethoscope. that will tell you if its inside or out and front/rear etc.

 

[Paul I]

G'day, The washup to this was that Idler Gear (A) had lost some teeth and had damaged the Injection Pump gear.
There was also a tight spot in the timing chain.
regards Paul