300tdi Death Knock???

[08Bender]

Hi Guys,

So, a buddy has a 98' Discovery 300tdi with a very bad rattle :(

He is an ex-mechanic so he has some idea and several have looked over it by now. It is best described as a heavy rattle, sound is deceiving but best we can gather, cylinder 2 combustion chamber. When it started it was constant but it gradually went away over a few hours. Today I had a look, it will only do it when you rev it over 3000rpm and let the throttle snap back, starts about 1200, stops at idle.

He took me for a drive and it drives fine, no smoke or misfire, just a heavy rattle occasionally. We got lots of intereast around the Brissy Uni campus!

He has had the sump off, checked big ends and mains. Torque converter disconnected, still there. Same with ancillary drive belts off. He's had the timing cover off, rocker cover, and it's not exhaust. Was planning to check vac' pump next, only because stethoscope suggested so, however might just be coming through cam shaft?

I suggested I ask here before he takes it to Austral, as I'm sure someone here more familiar with the 300 has had it before. Open to silly suggestions to! :wasntme:

I'll post back once he finds out either way for future reference.

Kind Regards, Tristan

[rick130]

Seeing as you've checked everything else, I'd guess vac pump, they can make some odd sounds when on the way out, are a pretty ordinary bit of gear and that's where you are heading next anyway :D

Ordinarily I would have said big ends, particularly being a '98 and it could still be cam bearings, that's not unknown on 2 and 300Tdi's.

[justinc]

broken crankshaft is a possibility too if it is quite loud, don't larf i have seen one drive 250km with only the number 1 conrod holding the journal together, at highway speeds. i initially thought the balancer was loose, but as i tried to check it the crank pulley moved up and down. :eek: and double :eek:.

New crank and conrod a set of shells and all was well again.

It was also a 1998.

I have seen 3 1998 Tdi's fail through broken cranks, and 1 1997 that broke through a main journal and took the block with it. It had a knock for 2 days prior. You will need to remove the main caps to check, I take it he has already checked the big ends and found no problems then?




JC

[08Bender]

Hey,

He has had all the main caps off, oil is squeaky clean! Although anyone that would hear it would suggest its terminal, it sounds like its lost a big end, but they have been checked.

Oh, and it runs like new! Beside the sound of course :D

Tristan

[rick130]

Hey,

He has had all the main caps off, oil is squeaky clean! Although anyone that would hear it would suggest its terminal, it sounds like its lost a big end, but they have been checked.

Oh, and it runs like new! Beside the sound of course :D

Tristan

Mine ran like a scalded cat (for a Tdi :D) and every big end was terminal.

[justinc]

there are other possibilities;

gudgeon bushes, mistimed camshaft - this will allow pistons to kiss valves, broken vac pump pushrod/ internal valve, excessive crank end float,

keep looking :(

Also, while it is knocking loosen each fuel line in turn and see which cylinder is the culprit.

the flex plate could be cracked/ broken. that causes an awful racket...

jc