300D rattles/Knock

[Gerard]

Hi
I have recently bought an 87 300D and its producing a regular tick/knock at idle which disappears as revs increase.  It also runs a little rough as if out of balance and every now and again a "miss" occurs.  I have had the injectors checked and fuel filters replaced.  
The tappet clearances (as per Haynes manual) seem OK.  I would like to check the timing chain stretch but I cant find a mark for TDC on the Crank pulley.  Can anyone give any advice?
Thanks
gerard

 

[PhilT]

tdc should be marked up as OT on the pulley with degrees marked on either side of it.
Is it only knock/tap when cold? As alot of the merc diesel seem to do this, but are alright when warmed up.
Are the tappets hydraulic on your engine? could be one a bit faulty.
phil

 

[Gerard]

Hi PhilT,
The rattle is strongest when the engine is warm, I think one tappet rattles a bit too much though and I wonder if a bad tappet would also cause a combustion knock.
There are no marks on the pulley rim, I cleaned it with WD40 and wire wool to search for them!  There is a protruding dowel about 8mm diameter but I dont think its to do with timing.  
Can tappets be changed without taking off the chain, ie pull off sprocket to one side and then remove the cam?

 

[PhilT]

Check your engine number, if it starts 601 or 602
To change tappets,  set the timing on TDC,  you will have to do this on camshaft mark if you have none on crank pulley. remove the chain tensioner,  remove the cam sprocket, but tie up the chain to stop it dropping down. the chain may snatch down towards the fuel pump. don't turn the crankshaft untill chain is back on. undo the camshaft caps gradually in turn untill there is no tension on camshaft. remove caps, remove cam. BE AWARE OF A 'HALF MOON' UNDER THE FRONT CAM CAP WHICH CONTROLS ENDFLOAT OF CAM! sometimes with the oil it can stick to the cam so be carefull it doesn't drop down the timing case! tappets can now be pulled out.
if you fit new tappets oil everything up, refit cam and caps (don't forget half moon) tighten caps down in turn, make sure the cam is on timing mark, refit sprocket and chain. you may have to pull up on the chain to get it back on, make sure the slack is on the tesioner side of the cam sprocket. refit tensioner.
look about for another crank pulley if yours has no marks as these are needed to check for timing chain stretch, and its well worth checking. anything over 7 degrees of stretch needs a new chain and tensioner.
Phil

(Edited by PhilT at 6:43 pm on Oct. 25, 2001)