I'm still on my quest to track down the diesel knock on my 97 300 tdi (222,000 miles).
After putting on a new vac pump, the sounds is still there:

I checked the timing and found that it seems wrong. The photo shows an oily mark that the flywheel locking pin has left on the flywheel right next to the groove it's supposed to lock in.
Injector pump was locked with a timing pin.
The timing belt was changed 18months ago, could the belt have jumped a tooth? or the Pump timing changed somehow? Would this cause the diesel knock? It started this summer after towing a trailer up a motorway hill. Can I adjust the pump timing to put it right?
Any advice or similar experiences appreciated!

Yes pump timing can cause diesel knock if its to far advanced, however your does not look to be too far out.
It's easy to set it right, so still worth a go just in case.

Are you sure the knock isn't a big or little ends (conrod bearings) as towing up hill will put a huge load on the engine.

I can't be sure it's not the bearings. The noise is there all the time, at tick over and whilst driving. Was going about 50mph uphill with a 3/4 ton trailer, when there was a jolt and the oil light came on at the top of the hill, so pulled over and the light went off, so carried on, but noise has been there ever since. Have read about timing belt slip, I am puzzled as to why the timing is out.

White_Disco said:

Have read about timing belt slip, I am puzzled as to why the timing is out.

Click to expand...

The small amount of angular displacement of the timing mark as shown in your photo would make absolutely no difference to how your engine would run or sound, I have had a 98 Tdi in with a full 1 tooth displacement on the fuel pump and half a tooth on the camshaft, (bodged timing belt replacement by previous owner), it still was running/starting reasonably, no knocking.
Your description of the event where the oil light came on sort of shines a light on a bottom end bearing problem, I have heard that there were some late '97 early '98 Tdi's that had been found to have weakness in the big ends.
Also heard of camshaft bearings moving out of their positions in the block, that causes a big instant drop in oil pressure.
Hook up an oil pressure gauge and take a drive over a good cross section of normal type running, once the engine is hot your oil pressure at idle speed should not fade off to nothing, (most oil pressure light switches will stay closed right down to 7psi), so if your light comes on with the engine running the oil pressure is down to a dangerous, (for the engine) level.
Driving with that problem can only damage the engine further, if caught now you could save lots of financial pain.

id look at the pushrods and tappet clearances ,valve caps etc

White_Disco said:

I'm still on my quest to track down the diesel knock on my 97 300 tdi (222,000 miles).
After putting on a new vac pump, the sounds is still there:

I checked the timing and found that it seems wrong. The photo shows an oily mark that the flywheel locking pin has left on the flywheel right next to the groove it's supposed to lock in.
Injector pump was locked with a timing pin.
The timing belt was changed 18months ago, could the belt have jumped a tooth? or the Pump timing changed somehow? Would this cause the diesel knock? It started this summer after towing a trailer up a motorway hill. Can I adjust the pump timing to put it right?
Any advice or similar experiences appreciated!
View attachment 91268

Click to expand...

Ive got exactly the same knocking noise on my 300tdi defender. Perhaps not quite as loud as yours but seems worse when the engine is cold to me. Ive triple checked the engine timing with no success, reconed injectors, valve clearances, manifold gasket and FIP timing (briefly). All of which ive had no success with.

After trying to find the problem for such a long time ive practically given up, and assumed it was either diesel knock, piston slap or some bearing. Either way its less noisy when warm. Sorry this is no help, your not alone finding the problem

Nice to have some moral support though! I've just taken the rocker cover off to check the valve clearances which are all ok. I stopped at taking the rocker gear off because one of the rocker pedestal bolts is rounding off, need to get a new one before putting the bolt grips on it. I'm going to hook up an oil pressure gauge, which will either point to (or rule out) big end bearings and then take the pushrods out if the oil pressure is ok. So far I've changed the manifold gasket, decat downpipe, vac pump. Thanks to all who have offered advice and suggestions. I'll post the oil pressure test results when I get them.

Plugged in an oil pressure test kit today. The readings are follows, I think they look ok:
tickover 750 rpm: 24psi,
1500rpm:40psi,
2000rpm:42psi,
3000rpm:44psi.
I've just bought a mechanic stethoscope to listen to the noises. Loads of noise coming from the timing case especially around the injection pump pulley.

Had the rocker gear out, all looks ok, push rods are all straight. Starting to think it's more serious, small end bearing perhaps. I solved the mystery of the oil light coming on at the top of a motorway hill now as its happened twice since. Symptoms are: loss of power, jolting and engine stalling when finally pulling over. Cause: overfilled fuel tank with Jerry cans before setting off on a long journey. Cure: remove filler cap and carry on for about 30 miles until used a gallon up! Engine still noisy and slightly down on power though, starts instantly with no smoke at all. How can I check for small end wear? Can it be done from below with the sump off?

The saga of the noisy 300 tdi continues, especially after hearing the nice purring sounds made by other 300 tdi discos at the local show at the weekend. I've used the stethoscope to go round the engine, the loudest noise seems to be coming from the injection pump pulley behind the timing cover. Cylinders 3 & 4 make a nice purring noise but near 1 & 2 there its a bit higher pitched and louder. Engine still noisy nearly a year after it started suddenly one day on the A30 in Cornwall sitting in traffic. Recently has been using about 1 litre of coolant per week. K-Seal didn't stop it although has slowed down the coolant loss. There are no bubbles from the thermostat housing when parked fron uphill. Before I take the cyclinder head off, could it be the injection pump (it's not the sound of air being drawn in, I know that sound!). Mileage is 235000.