Looking at a low mile 2009 5.3 engine from a Silverado. The engine runs and is in the truck still. The motor looks like it just rolled off the assembly line, and other than the expected dirt and dust, it is nice and clean. There are no oil or coolant leaks but the oil pressure gauge inside the truck will read about 40 at idle and then slowly drop to 0 and trigger the "Low oil pressure/stop engine" message. The needle on the pressure gauge will drop even when reving it a bit.

The guy said the truck runs fine but just started displaying that message. I have no reason to believe the oil pressure is bad because the engine idles silky smooth and doesn't make a sound that it shouldn't.

So where on this engine can I hook a mechanical oil pressure gauge to so I can tell if the pressure is fine and its just the sender that is going? I know I could use the oil pressure sender hole, but that is buried at the back of the engine pretty much under the cowl. Is that the only place?

Use the hole for the oil pressure sender. If the pressure remains good with the mechanical gauge, you're already halfway there for replacing the bad sender. If the pressure drops off with the mechanical gauge, you are still halfway there for removing and cleaning or replacing the filter that sits under the oil pressure sender that feeds the DOD oil manifold, which is where I would suspect the problem is.

It looks like I can get to the oil pressure sender, but will I be able to get to the oil screen under it with the intake manifold still on the motor and in the truck?

Also when looking at the engine today we started it up and it had 40psi at idle and after it warming up the gauge slowly dropped to 0 and the "low oil pressure/stop engine" message came on. Shut the engine off and instantly re-started it and it showed about 40spi again.

Does this sound like the oil pressure sender/oil passage screen or a internal engine problem?

Is the deep socket to take out the sensor a 1 1/16" or is it special gm tool?

You need the special socket to remove the sensor. You can probably get it at most parts stores, its called gm/chrysler oil pressure sensor socket. The 2 most probable causes are either the sensor or clogged filter, it's very tight, but you can pull both of them with the intake on.

Thanks, I'll give it a go tomorrow morning. Is the filter inside the cast riser that is bolted to the block/intake valley? Is there a gasket under that riser? You wouldn't happen to know what size of threads the oil pressure sensor are so that I can get a fitting for my mechanical gauge? I just use a old autometer mechanical oil gauge and plastic tube for temporary installs/checking pressures.

There is another choice, but an '09 engine may not have this type of turn-around on it.





This is a 2000 LS1. Not sure when they changed the turn-around, but the GM "Muscle Car" pan kit I got for the '57 has the later type without the nub on it.

I got the sender unit and oil screen out, but am having a hard time finding a fitting that will thread in place of the sender so I can hook up the mechanical gauge.

The screen did seem fairly dirty, it even had some gritty grains almost like sand stuck to it. Its nice and clean now, but as I posted above I can't find a fitting to thread in place of the oil pressure sender so I can check the pressure with a mechanical gauge.

It is such a pain to get to while in the truck I don't want to put the sender back in and see what the dash gauge says, I would rather confirm with a mechanical gauge.

I think it's 1/8 npt, but not 100% sure. I forgot to look at work today to see what fitting it is. I don't remember the size, I just know which one in my set it is lol. If you had the correct fitting, it would have been nice to run it before pulling and cleaning the screen, just to confirm. The senders are cheap enough, honestly I would just grab a carquest brand, standard brand or ac delco sender to stick in and be done with it if you can't find a fitting. If it's not bad now, it will be eventually....

Whatever the fitting is, it is not included in the standard oil pressure gauge plumbing kit. I think I found a fitting that will work and will try in the morning.

In my city in Canada even a generic oil pressure sender is $80+tax. So before I shell out almost $100 I will at least try the mechanical gauge.

Here is the fitting/size.

Your other option is to look right above the oil filter. If there is an oil cooler on the truck there may be another port to hook a sender to. If it doesnt have a cooler it has a block off plate with a nipple coming off it. Simply drill/tap it for 1/8 NPT. Thats where I hooked in for turbo feed/autometer gauge on my old LS swap (pic attached)

http://www.summitracing.com/int/part...2268/overview/

If it is a big fitting its 3/8-18 npt, if it is small, it's 1/8-27. You probably have the large one since the small size is pretty universal and should be in about any oil pressure test kit.

Well I found a brass fitting that fit and I could adapt my gauge to.

Happy to report that the engine holds 37psi hot idle.

But, do you know if the sender is bad or if you corrected it by cleaning the screen?

So what ended up being the problem? DOD AFM delete?