54bhp cdi idle rough as nails in a tin box.

[Heinkeljb]

Could be cam chain? Try lifting the cam chain off the sprocket - the slipper auto tensioner is known to break.

John

[pinger]

Could be cam chain? Try lifting the cam chain off the sprocket - the slipper auto tensioner is known to break.

John

If the above is suspect - investigate ASAP. If the chain jumps the sprocket your motor is toast.

[Mr T]

Agreed cam chain sounds more plausible or maybe hydraulic cam follower. My car makes a rattle on first start up sometimes & I think it's a dodgy cam follower that takes a few seconds to pump up with oil. http://www.fq101.co.uk/how-to-guides...ne/412-tappets

[classic123]

Well thanks everyone for the input.After doing some research and speaking to some cdi owners in other forums, It turned out to be the rattly clutch system rivets broken, which I had been told by quite a few on other forums.

[classic123]

I think this could be the straps on the clutch mechanism have failed. I had this happen many many years ago. I thought it was a big end bearing failure, as that's what it sounded like! The car ran & drove fine, it was only on tickover it made the noise, knock knock knock..... I drove it for a few days to work & back. Then one morning it wouldn't select a gear, just a thuding sound.
On investigation the finger springs on the clutch cover had inverted because a couple of straps had snapped. New clutch sorted it out.

Thank you. Spot on.

[Mr T]

Glad you got to the root of the cause. Some faults are a real pain to diagnose!

[classic123]

Glad you got to the root of the cause. Some faults are a real pain to diagnose!

Just orderd the new clutch kit. Hopefully it arrives by next week.

[tolsen]

My 450 Cdi having neary made it all the way to the moon in terms of total mileage developed a worrying metallic clunky rattling sound a months ago. So bad I did not dare even starting engine so has been riding my push bike to get around.
Found the fault yesterday. The exhaust is the culprit. A baffle or pipe inside is loose causing a loud metallic rattle.

[classic123]

Sachs Clutch kit has arrived and it is being fitted next week. I have had various prices for labor, some have been outright ridiculous but have gone with an enthusiast mechanic who also has a 451 so fingures crossed.

Update : The car has had the clutch changed and it is driving perfectly without any strange rattle. It pulls smoothly and gets to motorway speeds effortlessly. Hoping to keep her for much longer now.

Thanks to all on here who commented and helped.