[scotty325]

Hi Guys,

I’ve been scouring forum posts and various other sites for clues as to why my e90 n52 engine was producing a weird rattle/noise at idle.

Due to many helpful posts on here I was able to ascertain that it was not the oil filter or filter gasket and without any leaking from anywhere else on the engine it was beginning to look like it could either be the water pump (pulley or the pump itself) or the alternator pulley. I removed the belt and ran the car briefly to see if the noise was gone - it was still present with no inclusion of the belt so I moved onto closer inspection of other parts.

As you are all well aware it can be very difficult to pinpoint sounds of an operational engine, though it seemed to be localised to the oil filter/oil cooler assembly. Having taken off the oil cooler to check and replace the gasket there I decided to give the cooler itself a bit of a clean and there was a rattle present in the unit.

From the oil part of the cooler came two small pieces of plastic - one of which looks like the little clip/tab part that are present on most electrical connectors and the other looks to be some sort of small hose/plastic pipe or fitting.

Question is now - from where have they come to be in the oil flow of the engine and what are they? If anyone has ever experienced similar I would love to hear from you. I just wish to determine I don’t have a much bigger problem than I am already aware of.

For further information the oil filter is in good repair, there was nothing but a few tiny metal shavings in it (which I believe have come from the engine being replaced in the past) and there are no oil leaks.

Thanks!

[StradaRedlands]

Good that you found the cause, but sheeeesh, why on earth are there plastic bits floating through your oiler system??? I don't know the oil flow route, does it go through the cooler before the filter or after the filter? Presuming pre-filter, but ???? Guesses it got into the system during the engine install. Unfortunately the rest of that work is now suspect...

[e90yyc]

Can you describe the noise in any more detail? Was it present only at idle, or did it remain when driving? Did it go away once the engine was warm?

Sorry—I have nothing to offer other than questions of my own .

[scotty325]

e90yyc,

Noise is only present at idle, regardless of engine being cold or warm. It does however, not occur when before the engine has settled at idle speed on cold start (when it sits at 1000rpm for a minute or so before returning to its idle at 6-700.

Noise is a bit reminiscent of a refrigerator that needs a service. A rhythmic vibration or frictional sounding growl which seems to have no relation to the primary engine components.

Update on the oil cooler and pieces as above:

Noise still present.

Next thoughts are alternator pulley bearing/ pulley and power steering pump or pulley fail.

🤔

[NZE90]

I had a very similar noise in my engine. Turned out to be the oil filter bypass valve inside the oil filter cap. Have you checked that valve? Those plastic pieces could possibly be from the bypass valve.

[NZE90]

The easiest way to pinpoint the source of the noise if you don't have stethoscope is using a long screwdriver. This video will explain it better than I can.