[urq] rear main seal?

[Ed Kellock]

There's a noise coming from the engine.  It sounds like a really bad
bearing squeal, but it's coming from the back of the engine.  It seems to
only be present when I have driven it for a bit.  If I stop and restart
the engine it goes away but if I rev it, it comes back.  I removed the oil
fill cap and rev it and no noise.  I seem to recall discussion of noise
caused by leaking rear main seal on turbo cars with no bypass valve.  Is
this a possibility?

Ed