Help! at wits end - Disco 300 tdi still knocking despite rebuild

[benthng]

300 tdi engine knocking at idle with significant white smoke when cold start. Knock gets louder under load like switching A/con on or Auto Gear engaged.

Tried everything i could think of but cant get rid of of the loud knock which goes from piston slap clack-clack-clack at idle to metallic thunk thunk thunk when A/con is switched on.

I already check / did the following in chronoligical order but no solution:

1. Changed valve stem seals & adjusted valve lash 0.2mm - minimal adjusment required, no cure

2. Checked turbo impeller for oil and freeplay - no faults

3. Checked for rocker shaft / pedestal / loose bolt stud faults - no faults

4. Checked with stethescope sound like at top of block below head - not vacuum oir fule lift pump

5. Remove auxialary beltings - same knock, no joy

6. Retarded FIP timing as much as practicable - smokes, slightly less knock but real sluggish

6. Open T.case checked timing and various adjustments to cam and FIP - same knock, no cure

7. Checked Crankshaft pulley key way - its perfect

8. Ran engine without timing front cover - same knock, no faults found

8. Bosch specialist tested injectors, cant hold pressure - change 4 nozzles, no joy same knock

9. Specialist rebuilt pump - new plunger coz keyway damage and new supply pump, same knock

Then the current biggie but still no cure, knocks even louder:

10. Engine out, top and bottom off

- change piston no.4 (old injury with broken valve stem... another long story)

- changed con rod no.1 coz piston height unecven front higher than back by 0.3mm

- inspected crankshaft / cam shaft in situ - bearing / lobe surfaces looks good

- inspected auto gear flex plate - not broken looks serviceable

- Replaced all little end, big end and main bearings (bearings looks good but small end loose)

- rechecked crankshaft thrust bearing - still std size coz oversize cant fit in at all

- replaced 1 bent pus rod and 1 damaged tappet slide - other all ok

- fitted 1.4mm elring head gasket (all pistons below 0.6mm and its got a new cyl head)

Retarded FIP timing but still knocking miuch louder than my 23 year old 200 tdi, but less smoke though. Looking back I should have remove the crankshaft, cam shaft and oil pump but what else should I do other than to pull the motor out again.

Sorry for long post but I really need your collective expert advice.

[benthng]

Listened carefully again last nite (after rebuilt);

the thunk thunk thunk mid block noise seemed to have quietened down but the valve train / upper cyl noise very loud and harsh (much louder than before rebuilt) .... will recheck valve lash / recheck rocker & pushrod ops / recheck timing and report back.

ps: cyl bores at last rebuilt looks visually ok, crosshatching still visible, no pronounced lip at cyl top.

[benthng]

Sorted out, it was just a timing issue. Cam was 1 tooth retarded and fuel pump was 1 1/2 tooth advanced. Thereafter Fine tuning of fuel pump pulley. Sorry about the false alarm.

[PaulN]

Your competancy is way beyond my 'league' so I can't help but have been reading with interest.

Glad you are sorted - though what a trial. At least you now know what is defo okay!!

My question would be was it through a slip up in timing belt fitment or how did it happen?

[benthng]

Yep root cause was timing problem and a series of mishaps.. Started with aggressive tuning of fuel injection pump and turbo boost 22 psi.. Happy disco .. Over torque rocker stud led to loose pedestal and a broken rocker shaft .. Decided to overhaul cyl head with new valve rods and springs etc also new rings crank and big end bearings real happy disco.. Spring no. 3 broke... Costly repair .. Not so happy.. Then slipped belt and broke spring no. 4 broke.. Now all fixed but starter solenoid has gone bad. It's tough loving a LR.