So I have a 1990 Yota Pickup with the 3.0 V6 5speed. The engine was replaced before I bought it with one that now has about 80-90,000 miles on it. The frame has closer to 190,000 on it.

Basically I'm getting this strange rattle/gurgle noise from about 1800rpm to 2200 rmp. It usually happens when I'm cruising in 4th or 5th gear and doing about 45-50mph. It happens whether there is a load on the engine or not. If I punch the gas and get the the rpms out of that range then the noise stops. It does leak coolant when sitting overnight but I don't think its coming from the water pump area. I'd have to look closer to be sure.
This is the 2nd Yota pickup I have owned that made this noise and the 1st one blew a head gasket so I'm pretty nervous about it.

I'll post a video ASAP which I think will make things clearer.

Any advice would be sweet!