O-200-A engine noises
I have a very neat C150M and it's serviced regularly as required. Lately, there is a noise from the engine, similar to a turbo whistle but louder. We have had the alternator rebuilt, thinking that there may have been a bearing or brush causing the noise, but that didn't fix it.
It's there with the engine covers removed, so it's not a wind related whistle. All that's left is the starter or the vac pump.
Has anyone had a similar noise? Apart from the noise, it goes well. Compression is very good, doesn't burn oil and plenty of vac.