Hi all,
It is probably a general question about 4.3 engine.
I have 98' Astro with 200000 miles on it. It was developing a tapping noise that could be heard on transition from high revs to idle. A few days ago I started it in the morning and I heard this didtinct tapping noise, which sounded like a lifter to me. It desappeared as engine warmed up. I drove the van for couple of days and that noise never came back. Yesterday I was driving it as usual and after one stop that noise came back when I started it hot. It would disappear after a few minutes of driving. also I noticed that when it knocks the oil pressure is all over the map - low at low rpms, and tops up at higher rpms. When noise stops - the pressure is in the middle at all rpms. Any suggestions before I rip it apart to change the lifters?
Thanks in advance.
Also my coolant disappears, oil level is OK though, and no traces under the vehicle.

 

Oil is clean, will do rad test today, thanks.

 

No bubbles in the rad, and no white smoke. This morning was cold and that tapping noice was really pronounced, it muffled down quite a bit after motor warmed up. But comes back if I shut down for a while or idle it for a while.