Complete novice with hopefully simple probs

Hi

I have a 1997 110" defender, two owners from new, one a farmer and the other a gamekeeper.
The 300 tdi engine has 100,000 miles on it and when driving it occasionally sort of rumbles and a dirty great puff of jet black smelly smoke is forced out of the exhaust, the landy then takes off like a race car till a perhaps another 20 miles when it does it again.
The engine burns no oil as I check it regularly and it doesn't go down on the dipstick, is there a fix for this?

Second problem is a I noticed a squeaking sound which I thought might be the fan belt, closer inspection and the noise was coming from I guess you'd call it the fan belt tensioner [it's the small pulley forcing belt downwards top left]. A drop of WD40 squirted in this and the noise stopped but there is play in this top pulley, you can move it with your hand so guessing a worn bearing.

What do I need to buy to fix this as never done one before, is it a hard or easy job? and where's the best place to get the part?
Lastly how urgent is this? I know it needs doing but my landy is my only car so do I have to stop using it immediately.

Many thanks for any help/advice lad's, much appreciated

Brian.

Change oil and filter a good 10w30 dino oil rated for diesel, fuel filter, and air filter, might want to put in some diesel treatment in the fuel tank, just in case it might have some moisture. low fuel will cause condensation in the tank.When was timing belt replaced? If it hasn't been changed do it sooner than later, when they break it messes up the engine

Thor1950 said:

Change oil and filter a good 10w30 dino oil rated for diesel, fuel filter, and air filter, might want to put in some diesel treatment in the fuel tank, just in case it might have some moisture. low fuel will cause condensation in the tank

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WoW! thanks for a super quick reply

All off what you advised are on the cards and will be done shortly I must admit to always driving on the empty [well red], we don't really go anywhere so it's rare that I put more than £20 in and run that down to the red again

When was the timing belt changed last? If it hasn't been changed, then do it sooner than later, if it breaks can really mess up a engine.
Also look at checking and greasing UJ's , change oils in the trans, transfer case, and front and rear diffs. check for oil leaks at the pinion seals, check brakes aslo with a visual also look for leaky axle ends

Thor1950 said:

When was the timing belt changed last? If it hasn't been changed, then do it sooner than later, if it breaks can really mess up a engine.
Also look at checking and greasing UJ's , change oils in the trans, transfer case, and front and rear diffs. check for oil leaks at the pinion seals, check brakes also with a visual also look for leaky axle ends

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It was bought from a dealer and was supposed to have had a full service [I have the bill and check list for this], you can see all the mud and crap had been scraped away from all the axle and gearbox fill plugs. I have had it a few months now and it doesn't leak from anywhere, although new to this motor 20 years ago I had range rovers and a 109" so have always known leaks with this type vehicle
This one appears to be leak free [why do I wish I'd never said that]

double check the timing belt thing then, just make sure

I have a Defender 300tdi- 130, I have a squeaky belt, turned out to be the steering pump on the way out..then it went!!
Apparently the bearing in the tensioner is prone to wearing too. I replaced the beaing- job done.