D22 YD25 Engine Vibration problem

[pierresmith]

Hi,
I have a 2004 Navara D22 with the YD25 2.5TD engine.
I restored the truck last year after buying it as a project, did a lot of welding to chassis and rear tub and had a full respray, looks really smart now.
Only problem I have with it is an annoying vibration coming from engine bay. It's worse at around 1700 rpm, it seems to resonate quite badly at this level of revs, so you feel it most when driving around town and changing through the gears.
The faster you go the less you hear it, so the vehicle cruises along fine at 60mph with no issues.
Driving around town it feels like hard work though, the vibration takes the fun away from driving it.
I'm quite sure that the problem is NOT wheel bearings/alignment/wheel balancing/propshaft UJ's or centre bearing - all these items have been checked and replaced where necessary.
You can actually hear the vibration when the car is at a standstill and you rev the engine - it's a droning, deep buzzing noise.
At it's 1700 rpm peak the droning causes body panel shake, that's the best way I can describe it.
I am currently driving the truck with the front propshaft removed as it seems to lessen the vibration slightly, don't think there's anything wrong with the propshaft but it takes away a secondary point of contact with the engine I guess so the problem is reduced by a margin.

Any ideas guys, has anyone had anything similar? I'm wondering if it's my crankshaft pulley? I'm aware that has something called a harmonic balancer built into it which is supposed to dampen vibration, could this be it? When the vehicle is running I can't see the pulley wobbling at all though.
Only other thing I could think of is engine or transmission mounts, but I can't see any excessive movement in these components.

Would appreciate your thoughts gents, thanks.

 

[Old.Tony]

Have a really close look at the radiator fan, paying particular attention to the base of the blades - looking for tiny cracks. If it has a small crack it can allow that blade to flex - which means it might not bite the air as well as the others (force is off-balance) or it might decide to start chewing away at the back of the radiator.

I would suggest it is NOT in the driveline at all, if the droning can be heard when stationary. It could be in the clutch/pressure plate/thrust bearing. What happens if you hold your foot on the clutch (regardless of being in gear or not) - does that change the tone?

There have been one or two (so, quite rare!) reports of harmonic balancers breaking.

When you next do an oil change, inspect the dropped oil carefully.

In fact, you could examine the oil from the dipstick under an extremely bright light, looking for metallic flecks. This might tell a story about a bearing - possibly a big end bearing - starting to wear poorly.