1kz-te rough idle when hot

[divebrent]

Hi hoping someone on here can point me in the right direction.
Have a 93 kzj78 prado with the 1kz-te engine. A couple of months back it started idleing really rough once the engine got hot. and there is a knocking type sound coming from around the cam belt cover. I've taken the cam belt cover off and cannot see any oil leaks and there doesn't seem to be any unusual movement in the timing pulley. Also about the same time a whine developed which sounds like a belt being tight would sound like on a petrol engine. I've pulled off the vacuum pump to check the gears and there appeared to be some small metal shavings in there. I haven't driven it since this happened. Has anyone heard of this kind of problem before on a 1kz and can you point me to my next steps in diagnosing the problem. I'm reluctant to take it to a garage for them to turn around and say I have to pull the engine out and have a complete rebuild.
The weirdest thing is that the engine still runs fine, normal power etc, and only has the described symptoms after running for 15+mins and only at idle. Could it be something simple as a oil pump not supplying enough pressure when the oil is hot or is this worn timing gears, bearings type symptoms.
Also is this something I can fix without having to remove the engine.

Any advice appreciated.
b

[Jerry]

have a nosey at www.pradopoint.com , someone on there may already be aware of the problem

[divebrent]

Thanks Jerry, have had a good poke round there already without much success so far.
Anybody recommend any good diesel mechanics in the Wellington area.?

[Jerry]

Yep..... Andrew Farmer may know what the fault is 027 444 6803, otherwise Diesel Doctor in Petone

[divebrent]

Thought I'd better give an update. After many hours of fiddling about under the bonnet removing various parts and crawling around under the truck removing bits and bobs I discovered the cause of the noise and rattle. The 2 bolts that hold the thrust washer thru the main idler gear had sheered off about 10mm into the engine block and the gear was wobbling round inside the timing gear housing like a very wobbly thing. About 30% of the teeth on the main gear had found their way off the gear and into the sump. Found some cheap gears on TM and put back together in the weekend. Took for a spin around Red rocks and touch wood, there appears to be no other damage to the engine. As for the cause of bolts to fail, the only thing I can think of is that as the oil level was overfilled and either the oil "frothed up" and the gears overheated and caused unusual forces on the gears causing the resulting bolt failure or a piece of crap that's been sitting in the bottom of the sump for some time in the oil was picked up and floated into the timing gears and caused the gears to jump and cracked the bolts in the process. In anycase I'm pleased to finally have the wagon back on the road again. Now to find some mud.
Cheers