Oil pressure drops to zero when engine starts then goes to 60,while driving after warm,pressure drops down 4.3 V6 vortec engine

Did the mechanic drive the truck with a mechanical gauge to check the pressure ? The engine bearings or oil pump could be worn enough to allow pressure to drop at idle after it warms up.

Oil Pump or cam bearings

check oil pump,vacum leaks,oil pressure line leaks or air in line,etc.

ur oil sending sensor is bad it reeds the oil pressure

Hi,
you need to find out why the engine oil press drops so quickly to zero. If you continue to operate it in this condition, you will require an engine rebuild / replacem,ent!

You don't mention the year of the vehicle. If it is a late model, when the oil pressure drops to zero, a sensor sends a signal to the ECU of the event and the ECU shuts the engine down.

Good luck.

When the oil is cold it is thinner or watery and the pump moves more oil as it turns making the pressure go up. As the oil warms up it thickens and the pump moves less oil letting the pressure go down. Increasing the engine speed makes the pump turn faster, therefore it moves more oil and the pressure goes up. Changing oil grades will change the numbers somewhat, for example 10W40 will give you different readings than 5W30. I don't see any problem with the readings you put in your posting. I wouldn't be concerned until the warm idle pressure gets down to about 30 or a little lower. Hope this helps.

Two things...when it reads zero, is there any engine noise (tapping or knocking)? After you rev the engine does the pressure read normal at idle and function normally, or does it go back down? Either way, you should not drive the vehicle 'till you have a mechanical gauge (yours is electro-mechanical) put on there and the actual pressure is tested. The condition may be a bad sending unit, a bad bearing or possible obstructed oil pump screen. The repair is obviously different for each one and the price is as well.

Check the oil pressure with a test guage, if the finding are the same, the look at your oil filter, pump, pickup, or pressure relief valve.....

nothing ..normal low pressure at idle while hot ...but really should be thinking fresh oil change and filter soon..also what are the RPM's at idle hot in gear with A/C radio and other accessories running?

your oil pump is either weak or there is sludge i9n the oil pan. my adives is to have the oil pan dropped . chances are sludge is the culprit. as the oil get's warm the pressure should only drop slightly but pressure is generally dictated by engine rpm. pumps are gear driven so if it was a bad pump your oil pressure would start out very low at start up.