Thread: Elusive 300Tdi engine noise

Hoping you can help...

Vehicle is a manual 95D1 300Tdi.
Noise is difficult to accurately describe; a bit like rattling a sack full of empty glass bottles together. Very frustrating. The noise is quite loud at light loads, eg cruising at 70km/hr. Its harder to hear under heavy load and at idle. And very hard to hear under no load - ie revving engine whilst stationary and whilst it is cold. It disappears completely on over-run.

I could have created the noise when I recently replaced the timing belt. I cannot be certain because prior to changing the belt, the vehicle was my wife’s daily drive and she probably wouldn’t have noticed the noise. Its the third time I've changed the belt (did not experience this noise on the previous belt changes).

At first I suspected that I've got the pump timing too far advanced. I used a new pin kit that comprised of a pin to lock the pump and bolt with a pip or nipple on the end to screw into the bell housing and lock the flywheel. I rechecked the timing and it was advanced; looking up the bell housing hole the flywheel slot was about one slot width away from the center. Which was weird because I used the pin to lock it in place. I then check the diameter of the pip or nipple on the end of the bolt and it measures 6.1mm. I try inserting a 6.1mm drill into the flywheel slot and its way too big. So I found why my timing was advanced - the pin did not engage in the slot, just on the edge. So much for the timing pin kit I purchased that was advertised as a 300Tdi kit!

So I set the timing by eye; centralising the slot in the bell housing hole. A test drive indicates that the noise has reduced slightly but is still there. I then retard the timing about a slot width and this resulted in a loss of power, a slight reduction in the noise again but its still there. So maybe the noise is not caused by the pump timing. I've since reset the timing back to where it should be and had the timing cover off again to double check the cam timing (match cam sprocket with arrow behind it) and it looks spot on.

I've also checked the tappets and looked for exhaust leaks. They are good. I don’t think it's big end bearings since the oil pressure is fine and the engine was fully reconditioned 150,000km ago.

If there is a problem with the injector pump, could it result in such a noise and how do I check it? I think the pump is original - done around 380,000km. Any other things to check?

The vehicle still runs fine. Power is good. I've been waiting for more clues to present themselves; however, it seems the mystery is set to continue.

Thanks in advance,
Taz

Originally Posted by Tank

Check the idler/adjuster (compressor) bearings and the fan bearing in the timing cover, are the tensioner and timing idler bearings OK, Regards Frank.

Thanks Frank.
By idler/adjuster, do you mean those for the timing belt? If so, yes they were renewed with the belt. And I replaced the surpentine tensioner bearing and air/con belt tensioner bearing. I havent replaced the fan bearing in the time cover; however, it seems OK.