Worsening Noise In Engine

[lloydjv]

Howdy, this is my first post, here but I hope some Celica genius out there can help me narrow down a noise before I begin tearing into this thing. We have a 1991 Celica GT m/t with the 5sfe. This block only has 30K on it, but the noise that has developed is coming from underneath and behind the crankshaft pulley. my first thought was a main bearing, but there is no good reason for that, and the last time I experienced that, the noise was much different. Anyway, this noise sounds like the noise a loose timing chain would make on a truck. I understand this model engine uses a belt. The noise starts after the engine warms up a bit and the idle drops back to normal. it is difficult to hear at highway speeds, but idling at a stop you can very well hear it outside the vehicle. I hope someone can point me in the right direction soon, as this noise becomes more prevalent every day. Incidentally, there does not seem to be any lack of performance, but there is some vibration, nothing severe though. Thank you.

[rezzle]

Might be worth removing the belts and running it.

No noise wth no belts means something other than crank and cam. IE) waterpump or alternator etc.

EDIT: don't run it more thank 30-40 seconds .. remember you have no water circulation with no belts.

[lloydjv]

Thanks for the help on that one. I forgot to men tion that I had already removed the belts, and the noise remained. I did raise the front end and listened with various objects around block until I narrowed it doen to the area directly behind the crankshaft pulley, but I don't know yet what is causing it.