The oil pressure on my 98 just started dropping to 0 when stopping. it recovers when under load. Anybody have any idea what would cause this?

 

No oil in there will cause that. An oil pump going too.

 

How many miles are on the truck? Are there any unusual noises coming from the engine? Does it stay running? Does the gauge move smoothly or does it just quickly drop to zero at idle?

According to GM, the oil pressure should never drop below 6psi at 1000rpm, 18psi at 2000rpm, and 24psi at 4000rpm. The only real way to verify what the gauge is displaying is to install a mechanical gauge at the back of the block...

 

Truck literally just broke 100K mileage. Runs fine no unusual sounds, not drop in rpm at idle just the drop in oil pressure. it is a sudden drop to zero at idle (although not always - maybe 50% of the time at a stop light though i don't have a lot of data to go on. i only drove it about 8 miles home once i saw the problem.

 

Well, from that it sounds like a faulty sensor. The sensor should be located to the drivers side of the distributor off of a standoff w/ 90* fitting on it. My book says something about a special socket to use... Never done this so I don't know if it is necessary or not.

Chances are that if your pressure were dropping that low, your engine would have been toast. It really should have shut the engine down if it were truely that low. You would start to hear the lifters tapping before the bottom end would go.

 

Any idea what the part number is? My Haynes manual doesn't even list an oil pressure sensor or pressure regulator for topics??? (Glad i invested in that!)

 

Get on the web and punch up autozone or advance auto or whoever and look up the part . If you can buy it, it exists?? Picture might help too. Yes the location mentioned is the correct one as far as I know.