Please help me 98 6.5 diesel 200000 miles runs great no noise but at hot idle oil pressure drops really fast to zero and stays there until you give it gas. cold start at 60 -70 psi hot driving 60 mph around 40 psi but hit brakes its drops to zero at stop light but no noise and runs smooth this is with a new GM ops. Can I check it with a T fitting at turbo line or at ops.

 

Leave the turbo line alone there is a port though near top of the oil filter housing on the engine block 1/4 inch NTP use copper line
Check and clean all grounds especially the one on the back of the passenger side head not making any noise at 0 PSI sounds like a ground issue.

 

Mine does something similar, also with a new OPS. Except mine bottoms out at 10 psi.

Once the oil heats up the PSI nosedives. While some drop is understandable with lower viscosity, but 10 psi is right on the line. When it hits 9 psi the "Check Gauges" light comes on.

 

Another thing to do along with checking and cleaning the grounds is Google battery terminal mod for G.M. this will make a big difference on these trucks.

 

Thanks checked grounds and then installing oil pressure gauge but if the gauge says zero wouldn't the ECM kill the engine?

 

No but it would shut off lift pump.

 

Ok guys I put an mechanical gauge on it ran it in drive way didn't take for spin but at cold idle it had 50 psi and would drop as it got warmer lowest it got when themest temp opened was about 15 psi. Rev it up alittle goes past 40. Gona take for spin in a couple days and see how it is then but what would make it have low psi at idle and good at speed. Truck idles at about 700 rpm so even if it drops to 10 that's still ok right? Any more ideas ?

 

Yeah that is fine as long as it doesn't drop below 7psi truck will be fine.

 

ok took for spin and the oil pre. drops at idle as it gets hotter but still no noise and not rough like no oil pre would be. no shavings on mag plug. hot idle pre. was a round 7 psi and 30 at 2000rpm. Anymore ideas would be very appreciated don't wana pull it out with out trying everything .

 

As long as you can drive it and the oil pressure never goes to zero you should be okay.

Might just be a piece of garbage or some sludge in the oil sender unit orifice.