Sprinter low oil pressure and engine noise

A fluctuating oil pressure gauge along with engine noise isn't a good sign. While a clogged oil filter could contribute, the noises suggest something more serious, like failing engine bearings due to insufficient lubrication. Before jumping to the oil pump, have you checked the oil pressure with a mechanical gauge to rule out a faulty oil pressure sensor?

How do I check the oil pressure with a mechanical gauge? Is it difficult? I've never done that before. And if the sensor is fine, what's the next most likely culprit? I'm really hoping it's not the engine bearings.

You'll need an oil pressure test kit, which usually screws into the port where the oil pressure sensor is located. If you're not comfortable doing that, I'd advise against it, as incorrect installation could damage the threads. Given the symptoms, especially the noise, a failing oil pump is a strong possibility if the sensor is good. It's best to get it checked by a workshop to prevent further engine damage. I had a similar issue on an old truck once, and I wish I'd taken it in sooner.

Thanks, I appreciate the advice. I took it to a mechanic, and you were right – the oil pump was defective. The bill came to 755€, but at least it's fixed and hopefully I avoided any bearing damage.