Thread: Moaning/Groaning Discovery 2

Hi All,
Just wondering if anyone can offer advice here...
Mysterious moaning noise has developed, and it's not the fun sort, coming from my 2000 D2 TD5, 250,000km. It is a quite similar sound to a hot auto trans at the top of a long hill. I have had a new transmission fitted but not sure it's that - certainly it didn't do it when I picked up the vehicle a few months back.
It changes with revs not speed, and is present in low and high range.
I have a steering box on the way out, 'damp-almost-dripping' drop arm with some movement. Underside of PS pump was damp but I suspect the flange was loose; once tightened it has not got worse.
I have an unidentified dry sounding bearing in the front (fan, fan hub bearing, idler and AC bearing replaced, leaves PS pump, alternator and ACE. Used stethoscope but hard to tell as whole lot is noisy!)
I suspect the power steering or ACE but don't want to replace parts unnecessarily. There is some endplay in the ACE pulley but no leak.
The noise 'disappears' and 'reappears'. It tends to 'activate' after a turn or hard acceleration, and often vanishes on a slight uphill slope. It doesn't do it at idle or when revved in P. CORRECTION IT DOES MAKE THE NOISE WHEN REVVED IN P OR N!
When it goes, it 'fades out' rapidly and stays gone for a while.
The noise is usually present at start up.
The noise is not loud and tends not to be noticed by non-disco people (sell it now??!!)
Fluid is due for replacing but I don't want to do so until I identify noise.
Can air be drawn into the PS system through the PS box leaking seal? Or would internal pressure prohibit this?

Cheers,

Dave

Ok. Still no sign of the cause, but a bit more narrowed down to when it happens.
Always has an engine speed moan when starting after a long rest. Usually fades out after a few up/downhill runs (less than 5 mins). Does not get louder under load.

Noise returns during long runs on straights. It "fades out" after an uphill run (then stays gone for a while no matter what load/revs/speed etc). I was mistaken about the steering affecting things; its a steeper hill that helps; even a small one.

The only v minor fluid leak that occurs is a damp drop-arm.

It could be from the ACE block or my newly recon transmission?

Either way, any suggestions?

It almost sounds like air in a system getting bled out when car is on an uphill angle.

Could it be far worse like an improperly rebuilt trans and something moves rearwards when going uphill, then slowly moves fwds when on the level?

You may have read - I have replaced the Harmonic balancer. What a diff it made to the TD5 '2250rpm vibes'. I reckon a lot of harmonic balancers may look fine rubber-wise but the center bearing is stuffed like mine was!

Made no diff to 'the moan' though! Seems to be on the right of the motor...

I did the ACE filter 50,000 ago; needs doing but why would it be affected by hills? And why does it slowly return on the straight??

Downhill does not make it worse but it will not fade out on a downhill run.

Dave