Spider JTS weird whining sound - video attached

[Dahlen116]

Hello All,
I have 2003 Spider JTS with a problem that my mechanic and I can't solve. It has a distinct erratic idle (especially when cold) and once warmed up a whining sound at low revs from the engine. Once you rev engine the whine goes away. After research and forum posts we have:
1. Cleaned and tested pcv valve.
2. Tested for vacuum leaks around hoses, joins and inlet manifold. Tested for blockages in hoses.
3. Done throttle reset.
Here is a video of the sound from engine when idling after warming engine. (Note the sound is not there when engine cold although idle is erratic at low revs)
My mechanic is opening and closing oil dipstick hole thus releasing crankcase pressure as affected by the manifold vacuum - and you can hear sucking noise coming and going.

https://www.youtube.com/watch?v=RaJmIoUkx94

After closer examination on hoist my mechanic is sure it is sucking in through the rear crank seal.
Can anyone help explain why this would be happening. Blockage? In my online search for answers this scenario has never came up.
Great to hear from anyone with an explanation and possible fix.
Cheers, David

[poohbah]

Maybe I'm hearing the wrong thing in your video, but to me it sounds more like some sort of worn bearing noise than a sucking noise. The AC compressor bearing on my 156 was buggered a couple of years ago and was most audible at idle but would seem to disappear at higher revs. It was a while ago, but I recall it kind of sounded vaguely similar.  That said, I can't imagine your mechanic - who has heard it live - would be imagining a sucking versus sticking noise.

[bazzbazz]

Is it a manual?

If so, see if depressing the clutch affects the whine you are referring to.

[Dahlen116]

Thanks for the replies.
In reply to suggestions:
1. Regarding dipstick tube - will check the o ring next week  - car currently at mechanics.
2. Whine sound - clutch doesn't effect whine sound. Sound there also when depressed.
3. Regarding bearing noise - we are sure that the sound is associated with the crankcase ventilation system.
I should apologise for not going into more details about the tests we have done. Apart from the tests i mentioned in my initial post:
The first test we carried out was to squeeze the breather hose leading to the pcv valve - if you squeezed this the whine sound stopped. So we thoroughly cleaned pcv valve and tested. Whine sound still there. We replaced breather hose as well.
The whine sound goes away when you release pressure in crankcase  - so either lifting dipstick or undoing oil filler cap. If you place your hand over oil hole there is suction and sound reappears.
We have carried out compression test and replaced spark plugs in recent service.
During the recent timing belt change we noticed a lobe was worn on the inlet camshaft so we have replaced that - we presumed that this was the reason for the poor idle at low revs.
But erratic idle remains.
We do believe that the erratic idle and crankcase ventilation system (an associated whine sound) are related.
We relation to the suggestion that suction noise could be associated with rear crank seal - my mechanic has had experience with Volvos doing a similar thing and it was the rear seal.
The Spider rear crank seal is not leaking oil and the car doesn't appear to be using oil either.
So we are running out of ideas as to what is causing this.
Any thoughts and ideas appreciated.
Regards, David

[bonno]

I can only assume that the PCV valve was not only cleaned, but tested to see if was functioning correctly when under vacuum. Additionally, have you ruled out problem coming from engine ancillaries (Alternator, A/C compressor and P/S)?

[bonno]

Hi Dave
Found this thread that has a similar problem to yours on the alfaowner website forum.
https://www.alfaowner.com/threads/whistle-noise-from-engine-bay-oil-vapor-pressure-vacuum-in-camshaft-case-cover.1111946/

[Dahlen116]

Thanks Bonno,
Re: link - This is exactly what is happening in our situation. - The sound is coming from around this area (eg not over near alternator , A/C etc) and it makes sense that something is restricting movement in the breather system.
We haven't tried removing the spring and physically blowing and sucking through pipes.
The pcv cleaning process we used was to remove plunger and spring and clean both inlet pipe and plunger then replace and spray a quantity of carby cleaner while moving the plunger up and down on spring - the excess carby cleaner disappeared past plunger so we presume it is not restricting flow. I guess it is possible the spring has lost some of its tension but we thought it was working appropriately.
I read about the suction test with oil cap removed - if suction then pcv valve working - so we presume that it is operating correctly. Interesting that when you squeeze breather pipe the noise disappears.
We haven't concentrated on the air flow side before the throttle body - is it possible the inside of the throttle body needs a clean, and check butterfly in there?
Apart from the sound, the cause is effecting the idle (and i presume performance) of the car.
I cant go and test at the moment as the car is at the mechanics.
But anymore thoughts would be great. Cheers, David