vibration

[alanc]

Hi all,
My 89 2.8td Jackaroo has had an engine speed dependant vibration for about 20kkm. It seems to be getting worse.
I have checked the exhaust system and looked for any loose items that the engine may set vibrating but have found no cause.
The vibration begins to come in at approx 2100 rpm, is worst at 2400 and is gone by 2600 so, it does seem to be some kind of harmonic. Fuel economy and power have not changed for 90kkm.
Has anyone experienced roughness or vibrations in their engine or has anyone suggestions?
Thanks and regards, Al.

[Harry]

Check front pulley.Some people,when doing cam belt, take the big bolt out of the pulley to remove it.Very difficult to retighten properly.Much better to undo the 4x 8mm bolts around the big bolt.If the bolt isn't tight enough it loosens,allowing the pulley to wobble and wear the crank nose.Motor vibrates more and more until either the pulley comes off or the cam belt breaks or loosens its tensioner and slips,causing bent pushrods,broken rockers and dented pistons.Anyway,its probably something simple like broken engine mount rubbers.
Regards,Harry.

[geeves]

Been there done that with the pulley I was lucky When we caught it the cam belt pulley was only being held in place by the fan belt tension and the locating spacer had a keyway that was 12mm across on on side and 4mm on the other. Had to replace this spacer and the missing crankshaft bolt and repair a hole in the cambelt cover. This failiur though produced a knocking noise just off idle rather than a vibration at 2100 but still very worth checking.
Ive had a similar vibration a couple of times on mine First time was due to a loose bolt on the crome intercooler cover I cant remember what the second one was but it was equaly serious. Best way to find is open the bonnet and have a look while someone gentaly increases revs till the noise is made or this range is excedded. Be carfull of rotating objects like fans and belts that find fingers to be very nutritious ie they eat them if you get to close.
If it doesnt make the noise with the bonnet up look closely at the bonnet hinges

[alanc]

Thanks Harry and Geeves, I will check the pulley.
Come to think of it, this motor has always been very rough at idle anyway, it smooths out by 1000 rpm but at idle it shakes about.
My motor has timing gears with the cam low in the block so, no belt.

This morning it was -1 C and I noticed that the vibration(2100-2600) was almost gone at mid warm up, after about 2 km, and returned after about 15km. Maybe the exhaust system is resonating and this changes a bit due to heat. I remembered that at times in the past it has been less of a problem at times. I just had'nt noticed that temperature may be involved.
Maybe the rough idle and the higher speed vibration are related but it has always had the idle problem and only developed the higher speed one over the last 20kkm.
Thanks again guys, Al.