noahkb80

morning everyone new to forum. Will complete profile here in a bit but wanted to get this question out there. Drive an 08 silverado LT1 crew cab. 200k miles . Had an issue for a while of no oil pressure on guage. Engine drove fine, got a little noise now and then but nothing to cause alarm. Finally replaced the oil pressure sensor and now the oil pressure rises and falls with the rpms of truck. If the nose is downhill its less prone to give warning chime and message on dash, most times coming to complete stop , the engine warns to shut off. Im not losing any oil. No leaks. I do get a little more noise though, but its inconsistent. Sometimes it taps really loud, sometimes not at all. Engine temp and drive time dont seem to have a specific effect. Its completely random. So looking for advice on where to look next. Oil pick up tube o ring? Maybe a bad sensor(got a cheap on off Amazon &#128533 or perhaps wiring ? I'm a DIY mechanic with limited knowledge so just trying to get as much guidance as possible before I do more complex work.

Oh and I did replace that little filter as well. I use Pennzoil High Mileage Full Synthetic & Wix premium filter
Thanks

Gumby22

It’s normal for the oil pressure to change with RPM. You want to see at least 10 PSI per 1,000 RPM. At operating temperature, typical pressure for these engines is +/- 20 psi at idle and +/- 40 psi at highway cruising speed.

The warning being triggered if facing downhill could be due to the sump getting partially exposed as the oil fills the front of the oil pan. If you’re gonna remove the pan to replace the o-ring, I’d suggest going ahead with the pump change. At 200k it could probably use replacing anyway.

noahkb80

my apologies. Didn't realize how vague my initial post was. The current situation is once i replaced the sensor , i went from. Always reading zero on guage no matter what ,but no warning, to the pressure guage following the rpms with at speed getting up to maybe 30 at the most , and falling to zero at idle. Occasionally, moreso if im pointing downhill, i will not get a warning and it will stop at what I would guess is 5, but majority of the time if at idle with no movement, it falls to zero and dings.
It does this every drive


I've had new sensor for a month check oil before each crank. No leaks. No loss. Sometimes it taps like hell, sometimes its dead quiet and drives like its absolutely brand new. And the symptoms don't correlate with cold or hit engine or weather or driving habits , it's completely random.

Again, I am no mechanic. My tools consist of a little pink bag with a few basic tools in it. I stole it from my ex wife..But im a fast learner and I do have access to probably the best mechanic alive today. He builds showcars for rich guys he finds out in the woods and in fields and restores them to values over $100K. He knows his stuff but i avoid him if possible because he's a raging a hole . So. Hopefully i can solve this on my own

kevinkpk

If you hear tapping, and low oil pressure on the gauge, I'd consider dropping the oil pan, and if you have to go through the effort, replace the oil pump. Sorry to say you will need more than your tool bag.

Rednucleus

What weight oil are you running?

noahkb80

Lol yeah. I know. Probably will just take it over the the family's house. I did notice the other day it seems to be causing,or be the cause of, a voltage drop. I think anyways. I thought it was my AC causing it , but I ruled that out. At idle, in gear, rpms sit almost to 600 and drop to 400 repeatedly like the truck is going to die. Light comes on. Dinging sounds. It will get worse the longer I leave it like it would eventually stall. I put it in neutral and throttle it up to 1000rpm. That's the lowest I can with my foot. It chills right out then and is smooth and quiet as can be.
I had been running 5w30 Pennzoil full synthetic high mileage. Just this past weekend I decided to try 10w30 just for the hell of it. It helped some , but not fully. Im in Texas so its ridiculously hot. Heat seems to worsen it also. The longer I drive, louder it gets. Last few evenings its been a little cooler, and if I baby the hell out of it and granny it around, it'll stay mostly quiet. But once I ever get on it or out on the highway over 50 or so, itll usually start to get louder

noahkb80

About to get under it today and clean everything. Oil all over the place underneath. I check it multiple times a day but notice no loss of oil, but clearly that isn't the case. Changed the plugs today and that eliminated my rough idle and hesitation on acceleration. Had some wet oil on the threads of #5 and #7 (drivers side , closest two to steering wheel) but none on the porcelain side. The whole bottom is dripping and dripping off cross member. Its dry back around the oil pressure sensor. The area inside that round chrome plate that pops out, cant remember the name, but its dry inside there. Again, im no mechanic by any stretch of the imagination. Im no dummy, just ignorant with engines. But I can manage. Only other thing in within the scope of my abilities is change the valve cover. After that, its looking like it's gonna go pay a visit to the fam and drop the oil pan and do the afm deflector shield and o ring and whatever else he says.
Sorry for slow responses. Fighting for custody of my 3 kids , so dealing with my 3 ring circus of an ex is a full time job.