Oil pressure fluctuations at steady hwy speed and rpm. Ok?

[OR VietVet]

I'll double check part numbers. Ya know, I had a bad leak before I got the new trans and they fixed rear main, I overfilled (3/4 quart or so) when I went on long trips because it was losing a ton. I don't recall it doing it then actually. Im about to change oil probably this weekend or early next week. I will add a bit extra and see.

By little bit, I hope you mean 2 quarts and do the "park on a downhill" and report what happens. I was surprised that you stated this problem had been happening before the work. Info like that is important to this back and forth process.

 

[olliec420]

By little bit, I hope you mean 2 quarts and do the "park on a downhill" and report what happens. I was surprised that you stated this problem had been happening before the work. Info like that is important to this back and forth process.

So whole story... Its been fluctuating since I got it in Aug 21. So this Yukon, I bought new in 09. I traded in in 11 for a new. The guy who bought this car from the dealer worked near me and I told him I wanted it back when he was finished with it. One time when I went to get an oil change in 2010 sometime, the guy said, "there's no oil in this thing, you been drag racing it?" It was at express oil change where you don't have to get out of the car. And I had been flooring it from every stop at that time (I was about 28 and with everything under warranty I didn't care) but I laughed it off. Traded in about 35k miles. The other guy got an extended warranty with it and around 55k miles ran low on oil and rings got stuck. They overhauled the whole thing under warranty at the dealer. All 8 pistons. I have the records. The paperwork states the codes and "customer states oil pressure fluctuating."

When I bought it back from him in Aug 21 I intended for it to be a toy and turn up the power and do burnouts etc. Then my 21 Sierra got hit and the 09 became daily. It took 3 months for them to fix Sierra and then when I got it back it still had some weird things in the steering (hit in drivers wheel dead center). I sold it to the dealership (they bought out my lease) and just decided to use the 09 as my daily since it had been running so well and I bought a mint 98 (my avatar) that popped up on craigslist as a backup and "classic" & "collectible."

Before I did the oil pan gasket and pick up o-ring and all that I had a wicked rear main leak. The previous owner had a hunting camp down a washboard dirt road so it got shaken and beaten to shit. I had been misreading the dip stick when I was checking oil often due to the leak. And consequently over filling up to a quart for about the first year I had it. I saw the fluctuating sometimes and then I would think it was low and add a bit but it really wasn't. I was over filing and it would stop. Pressure would also be higher in general when I was doing about 7 instead of 6 qts. So now that the leak is fixed I have filled it with 6 qts and have been seeing this fluctuation consistently. So I think starting out I'll put one more in and see what it does when I change oil here later this weekend.

It also has to go back to the trans shop this week. Getting some hard shifts and jerkiness when stuck in slow highway traffic on the interstate in backups. Like between 10-20 mph gear changes. So Im gonna change oil and let them look at it next week and then get it back on the road to see how the pressure looks. Its happened so long that Im not really worried about it, I just want to know if its a problem and if so what causes. Sucking air makes sense but I replaced the o-ring and the old one was shot and the new one fit nice and was good and round.

 

[olliec420]

By little bit, I hope you mean 2 quarts and do the "park on a downhill" and report what happens. I was surprised that you stated this problem had been happening before the work. Info like that is important to this back and forth process.

Oh and also, I don't know if that will help because it doesn't do it all the time. It does it steady RPM highway cruising for a while. So if I park it down hill right now, it's fine. Its kinda of an intermittent.

 

[OR VietVet]

Better understanding now. I am one of those guys/techs that only trusts my rebuilding prowess. Dealer techs take short cuts to beat flag time. The rebuild at the dealer, is suspect in my mind. If I need an engine or engine work, I either do it myself or get a Jasper engine. Have been involved with Jasper for close to 30 years and never had one problem with them. I hope you figure your problem out.

 

[olliec420]

Better understanding now. I am one of those guys/techs that only trusts my rebuilding prowess. Dealer techs take short cuts to beat flag time. The rebuild at the dealer, is suspect in my mind. If I need an engine or engine work, I either do it myself or get a Jasper engine. Have been involved with Jasper for close to 30 years and never had one problem with them. I hope you figure your problem out.

I would like to get a texas speed brawler series 5.3 and put in but that's not in the budget at this moment.

Its been running fine since (with exception of transmission issues and normal wear and cosmetics) since the rebuild. 55k to now 173k. I have been seeing this fluctuation but was never able to capture it on video til riding home the other day. Had a 6 hour drive and saw it right as it was starting to do it. I assume it's fine. Maybe oil pump. But if I get in to the front end, Im going to do it all. But if I start doing that I might as well rebuild and turn up this one instead of getting a brawler. Maybe I should try to find a junkyard LC9 and do it up as I want and then swap and rework this one too. I don't know. My neighbor had an incredible shop with every tool imaginable. He built several trucks and mustangs over there but a wild fire 3 years ago took it out. And now he/we have to rebuy every tool and that sucks because now prices are outrageous and the quality is shit and he's getting old so he doesn't know how much he wants to get back in to.

So I'm keeping an eye on it and making plans for the future unless someone says "STOP NOW, you're going to blow that engine up if you don't address that fluctuation right now!" But I don't see how that's the case if its been doing it for almost 2 years that I have witnessed and put 25k miles on it in 2 years.

 

[j91z28d1]

after reading all that.. I got nothing haha.

yeah it would be interesting to see what adding some oil does. do that before the oil change and test drive not after. it's kinda messy to try and get it back out.

my own curiosity I'd put a mechanical gauge on it and see what it's doing right off the pump. if it still does it, and you are sure it's not sucking air. the factory oil pressure spec is super low and it's lasted this long. I'd probably just drive and not worry about it much unless something changed.

does make me wonder if it's a oil pressure bypass spring that's kinda sticky

 

[olliec420]

I have a question... so I was just reading a web page about oil pressure fluctuations (generic and not specific to 5.3) and says quote...

"So, the first few seconds after starting the engine the gauge reads very low. It’s probably accompanied by some loud ticking noises from inside the engine. Then, the gauge suddenly shoots upward to normal and the ticking noise stops. You have the wrong oil filter installed. Many engines require their oil filter to have an anti-drain back valve that prevents oil from draining downward, away from critical engine components when the engine is not running. If the valve is absent, the oil supply passages inside the engine lose their oil. It will take a few seconds for the oil pump to fill the supply passages back up after the engine starts. Expect that problem to be worse in the mornings, after the car sits overnight. Install the correct oil filter and the problem should be fixed. Simple."

So I do experience this tick/knock when starting up after a while. By the time the gauges become active the pressure is already there but the tick/knock is right when I start. I'll add a video later next time I think to record. It was present when I first got the car back and a quick search said "welcome to the world of the high mileage 5.3." Ok no biggie. I know I have the right oil filter on and am about to change oil again this coming week and going to be using acdelco filter and mobil1 high mileage full syn 5w-30. But now Im thinking is there a possibility theres somewhere in the oil pathways that could potentially be sucking air (besides the pick up o-ring which I have already replaced). And while I had it in the trans shop, they replaced the oil galley plug for me so I'm not worried about that. Anywhere else? OR am I barking up wrong tree?

 

[j91z28d1]

I think the general idea that article is talking about is engines that mount their oil. filters either sideways or even upside down. the oil drains out and has to be refilled on startup, so that delay is the valve rattle. the ls the oil doesn't really have anything to go, all the ls filters I've seen list a drain back anyways.

video for the other guys would be good, since they have more experience hearing afm and lifter failures. but I'm thinking you're just hearing a loose high mileage ls.

 

[olliec420]

video for the other guys would be good, since they have more experience hearing afm and lifter failures. but I'm thinking you're just hearing a loose high mileage ls.

Yeah you're probably right. Here is the video for grins. If anyone knows anything about it, I'd be interested to know.

 

[Geotrash]

Yeah you're probably right. Here is the video for grins. If anyone knows anything about it, I'd be interested to know.

That’s a lifter knock - usually caused by bleed down in a lifter until it gets oil pressure again. If it makes the same noise every time you start it, it’s likely telling you that it’s time to replace it.

As to your oil pressure fluctuations, we’re all chasing a ghost until you get a mechanical gauge on that thing and ride around with it for a while. Could just as easily be an electrical/indication problem as a mechanical one but I can’t think of anything mechanical that would cause a fluctuation like that except for the pickup tube o-ring.