I have a 1996 LT4. The analog oil pressure guage drops to zero and
the "check guages" light comes on when the car is idling. The needle
moves when the car is under acceleration and the light goes away.
I've owned the car since 1999 and this is a recent "feature".
There is plenty of fresh 10W-30 Mobil 1 and the oil pressure sensor
was replaced and didn't get rid of the problem. The dealer doesn't
have any suggestions. Anyone seen anything similar or have any ideas?
On cold start up do you hear any rattling or thumping from the engine?
Rod/main knock is very distinctive. If you don't, that's good. What
happens if you drain the 10W-30 (5W-30?) and replace it with 20W-50 or else
put a can or two of STP in the crankcase? If the oil pressure comes up and
stays up, loose bearings are looking good as a cause. With the viscosity
modifier in the oil, and on cold start, does the oil pressure go to the peg
or almost so? This would suggest the pump is okay if it does and point at
the bearings again. If the oil pressure doesn't go to the peg on a
relatively cool day, it points at the oil pump.
Whichever it is - bearings or pump, drop the pan on this bad boy sooner than
later and swap out both. Zero oil pressure for even a few seconds is bad
news. I have not tried this on a late model small block but on early small
blocks it was possible to change out rod and main bearings without pulling
the engine. The one-piece rear seal may make this impossible. Has anyone
reading this swapped bearings in an L98 or LT-1 without pulling the engine
or dropping the crank completely?
When the oil pressure drops, do you hear any lifter tapping??
It might be a bitch but if you could get one valve cover off
and start the engine, let idle and see if you can see streams
of oil coming out of the tops of the pushrods at the rocker arms.
You can also put a mechanical oil pressure testing gauge on
the oil pressure port to double check the in-car gauge.
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