TLDR at the bottom.
Some quick back story. I bought this car back in November and fully rebuilt the engine. Almost everything is new or has been worked on. New pistons, rods, rings, bearings, new crank, oil pump, springs/retainers, and every seal or gasket along the way. I had the engine bored out 20 thou (.5mm) so the cylinders are perfect, and I bought oversized pistons to match. I fully rebuilt the trans as well, new synchros, bearings, seals, and synchro hub sleeves. I could go on to list about 100 other things I've worked on.
500km into driving the car I start getting this squeaking sound, especially at idle and ONLY when its hot. When its cold, nothing.
I've removed the AC, Alternator, and PS belts, and it persists. It really sounded like it was coming from the oil pump, I took it off and inspected it to find score marks and scratches inside of it. Thinking that was my problem I replaced it, only for it to happen again after installing a brand new one.
I've had an oil pressure gauge right from first startup and it's always been 80-90psi cold and then 15-20 psi when hot at idle. I've pulled spark on each of the cylinders one at a time and it doesn't seem to change the sound at all. So I highly doubt it would be any of the rod bearings.
It still sounds loudest right from the oil pump/harmonic balancer area. I've tried gently tapping on the balancer while its running and squeaking and it doesn't change the sound at all. I've searched around the engine bay while holding a prybar up to my ear and pressing on things trying to listen for where the noise is coming from but still nothing.
It can't be any of the belts, it can't be timing tensioner since that would make a sound all the time, not just hot vs cold. Its not oil pump, I highly doubt its rod or main bearing. And it doesn't seem like harmonic balancer.
At this point there's only 2 things I can think of. Thrust bearing/washer on the crank is squealing once the oil thins out. (but why now? 500km into driving it, wouldn't the tolerances be greater after break in, not smaller?) Or water pump once the thermostat opens, maybe there more/less of a load on it now that coolant is properly flowing?
I'm running out of things it could be. If you can please take 45 seconds to watch the video and give your 2 cents I'd be super thankful!
Just as the engine starts to get warm
After warming up to operating temp