Z22SE Strange knocking noise coming from the oil pump housing area, possibly belt pulley

Hi everyone

I'm new here and introduced myself in the Introduction Section.

With my Vectra B 2.2 I am having some sort of anoying noise phenomenon that is giving me some serious fears that my engine might fail in the next weeks or even days.

I recently changed my cooling fluid and on the warm-up I realized the noise for the first time. It's a kind of knocking noise that comes from the timing chain end of the engine, while the engine is running on idle speed. More strangely it is only clearly audible when the climate is set to ECO, so that the compressor isn't driven. Reason fo that seems to be a slight increase of idle speed or engine load. On tip-ins or higher rpms the engine sound completly normal without any rattle or knocking, which shouldn't be so IMO if the timing chain had an issue.

Here is an example of the noise on my Vectra:

Another example I found on youtube is given here:

Using a big screwdriver as an stethoscope I manged to locate the origin of the noise to the oil pump housing area. Seems to be the loudest where the pressure relief valve is located. Got that one already out and saw some minor scratch marks on it, but it slides very smoothly inside the housing.

Well the noise got me kind of frustrated and kept me thinking of what might produce it in that area. Because the belt tensioner is fixed onto the engineblock right through the oilpump housing I thought that I could give it a try and removed the belt drive. With that the knocking noise was gone and a closer look to the tensioner pulley revealed that it has some bearing slackness. Put it all togehter again and even slight lifting of the tensioner from the belt makes the noise go away.
In that way I already orderd a new pulley. It should arrive next week and solve my problem when installed

I keep you informed

very good matey ,, were going to say take aux belt off , glad you have sorted it

Great diagnosis - a new belt tensioner will have it running smoothly again.

Hi again

So I finally managed to install my new tensioner pulley. Got it from eBay and quality seems to be ok. No more slackness on that bearing.

Disappointingly after the warmup the knocking noise is still there. Possibly a bit better than before, but still audible. Maybe tomorrow I try to recreate the early recording with the old pulley to make sure of it.

I also was able to examine the first recording with an analysis-software for acoustic development. With that I found out that the knocking is repeated every two revolutions of the crankshaft. Thing is that I have no clue what could produce such a noise down at the oilpump housing. Oilpump revolves with engine speed and pushes the oil through 8 chambers at every revolution. The counterwheel has 9 chambers and thus revolves with 8/9 of the the crankshaft. Waterpump revolves also with crankshaft speed an the two balance shafts revolve with double speed. Only the two cams revolve with half the speed and one failing hydraulic valve lifter could be an explanation. But that would mean that the noise should come from the cylinder head an not the oil pump housing :/

Any ideas or input what might be the source? Maybe it's just a design flaw of the engine and I never noticed it before

So... It's been already a while and I still have the noise. With now at least 2.000km more on the clock, it looks like it isn't serious at all.

But now I have the idea that it could be the belt itself which is causing the knocking noise. The belt has a lenght of 1030mm. On the web I found that the crankshaft pulley has an diameter of 166mm. Well, that makes an circumference of roughly 521,5mm, which is almost the half length of the belt. In that way an irregularity somwhere on the belt would excite the structure almost every two revolutions of the crankshaft.

Well over the weekend I try to have a look at the belt. Maybe I still have the old belt somwhere around and try if the noise is also there with it.

Keep you informed...

Take the belt off and support the engine and start it. If the noise is still there its internal.

If not its the belt, tensioner, alternator or aircon

Well thanks for the reply. But if you would have read my first post, you would know that I already tried that and figured that it might be the tensioner pulley. Obviously it wasn't

Oh sorry. Good idea though. So its internal then.

Oil pump i dont think really fail in these.

normally chains n tensioners.