Hi all, I've searched this topic thoroughly and have thus far found many contradictory answers (mostly on 7+ year old threads), so I'm posting this one hoping that perhaps as time has passed, there's been a consensus that I can't find for some reason - apologies in advance if it's here somewhere and I missed it.

My 2008 6spd base model has ~120k miles on it and is in otherwise perfect working order. However, towards the end of last summer it started having 0 PSI oil pressure at startup. Easily verified it is not the sending unit - can hear the tell tale engine noises that mean no oil pressure. A quick rev to 3k RPM fixes it, oil pressure pops back up to normal and behaves properly through entire RPM range/all driving conditions. Seems to be temperature sensitive as well. If outdoor temp is ~70F or above, the rev fixes it. If outdoor temp is below 55F, the rev brings the oil pressure up for a second, but it drops back to zero quickly thereafter; won't hold proper pressure at all like it does when warmer. Note: I only did the rev thing a few different times to test knowing it was bad for the motor - no flaming required Temp-sensitive nature of the problem further verified by the condition not occurring if the motor is shut off for a short time after coming to normal operating temperature - for ex, if I took the car to a lunch meeting, it wouldn't require the rev to regain oil pressure after lunch.

So far I've tried oil + filter change 3x times w/mobile 1 everything - no change. Car has always been meticulously maintained, has no codes, and no other issues. In other threads, I've seen everything from sludge in the oil pan blocking the pick up tube, to the oil pressure relief valve sticking open/failing oil pump. Posting this query now as I'm de-winterizing the car and don't want to continue doing the rev thing just to enjoy it for the summer. IF it's for sure the oil pump, I'm not interested in ripping the front suspension apart to get to/replace it and will probably just trade the car in for something else. But if anyone has a suggestion with a less involved remedy, I'd prefer to fix/keep it - absolutely love the car and enjoy moderate level wrenching - replacing the oil pump is just way too involved/not a project I want to tackle in the driveway/without a lift. Thanks in advance for your suggestions/wisdom.

 

Welcome to the forums. I wonder if your sending is slow to read, before getting drastic with anything if you could hookup a mechanical oil pressure gauge and see if you get the same readings. A antisiphon oil filter would help some, Maybe using a higher weight oil 5w-20 to a 5w-30 or 40 worth a shot.

 

Thanks Thomas - funny enough, I've been a member here for many years...potentially up to 22 years if this is the same corvette forum I joined when building my very first car (a 1977 L48)...just hadn't had a reason to sign in for a while, forgot my old password and no longer had access to the old email to do the reset thing, so had to make a new account lol.

Appreciate your thoughts - just looked up the mobile 1 extended performance filter I'm using and all the google results say they include the anti drain back/antisiphon valve, but please correct me if I'm/they're wrong about that. Sending unit-wise, there's no doubt it's working properly. These motors make a very specific type of noise when they're not getting oil - very easy to hear the difference when she first fires up with 0 psi OP, then gets it after the rev - literally a night and day difference that corresponds directly to what the needle is doing in real time. It's actually how i noticed the first time it happened - had started it to warm up and immediately starting taking the top off without looking at the gauges - i heard the motor's unique no oil pressure sound first, then saw the gauge at zero and couldn't shut it off fast enough...not a fun feeling when that happens lol.

The oil weight idea is interesting and I'm certainly willing to try it...but if she can't run her OEM oil weight properly, wouldn't that indicate a more serious problem all by itself?

 

OEM oil should be good unless it being driven hard. I have had several LS engines and they popped up oil pressure once started, never an issue. it almost sounds like the oil pump lost its prime, O ring on the pick up tube could be failing, which could be serviced with the oil pan off.

 

There is a possibility there is a problem with the oil pump by-pass valve sticking and by-passing on start up. A oil type cleaner might be something to try to free that valve. You wouldn't have good oil pressure with a broken relief spring.

 

Good call - I ran an oil system cleaner through it on the 2nd oil change/followed all instructions on the bottle - no change. Think I should repeat the process? If so, how many times to be confident it wasn't going to work?

 

Is it possible to leave the cleaner in the engine oil for a while? Valvoline makes a clean and restore oil that's good at getting any gunk out. Tearing into an engine is always my last resort. Years ago there was a guy that brought his late 50's Lincoln to me with very low oil pressure, 100k car. Installed a new pump and it worked great, tore the old pump down and couldn't see anything wrong with it, no visible signs of anything wrong with it. Normal wear, good relief spring, I had no Idea just wouldn't pump.

 

The mysteries are part of what makes the greaser life fun. My guess would be that Lincoln's pump had a tolerance worn too far down somewhere you couldn't see/feel, or something as simple as the pickup tube o-ring like u said above which i'm sure you replaced - we'll never know lol. Also likewise on tearing into an engine - that's y I really don't wanna have to do the pump. I enjoyed that type of major suspension/engine surgery much more 10+ years ago - there would've been a melling pump in that thing last summer just for the hell of it. but a decade and a couple shoulder surgeries later...much less appealing. that said, the car's at an age where i know the plastic bladders on the radiator are going to fail soon, it just started seeping the tiniest bit of oil from the valve cover gaskets, and I know the AC delco harmonic balancers on these things don't last long and is likely to go anytime too, so part of me says...just do it all the same time, save yourself a truck load o loot on shop labor, give yourself all kinds of room with everything taken apart, do both belt tensioners, a timing chain kit and the front main seal while you're in there, and if necessary call in a favor from one of your many gearhead friends to help drop the subframe and pull the rack...maybe one last monster project to ensure my knees will wear out before this wonderful car does...we'll see lol. but i really appreciate your help in trying to think of/try anything short of that - if I can kick the can down the road a bit, that would be ideal; last surgery was 4 months ago.

The flush I did before was one of the 'idle for 10 or 15 min" before oil change ones. Don't remember the brand now, but def one of the big guys (lucas, valvoline, sea foam, etc). They make cleaners that range from that to a few hundred miles, to 1000 mi. My problem with leaving it in is that means I have to drive the car like this - can't imagine it'd do its job if mostly idling for a long time. And while I'd like to convince myself the 3k rev at startup isn't doing "that" much damage to the motor due to the good synthetic coating/sticking to the bearings, cylinder walls, etc, the gearhead in me still can't quite get there...makes me cringe every time lol. Suppose I could arrange a 300+mi nonstop joyride if it's the last option prior to replacing the pump though, so if you think that could free up something important, lemme know. If so, where do you come down on the great Kreen vs sea foam vs MMO vs everything else debate?

 

Burdman I would say you have a unique problem but like all mechanical issues there is a reason for everything. Not a big fan of oil additives, but in your case it's always worth a try. There are people that swear by Marvel Mystery oil. No one seams to know what's in it. I know changing oil often flushes out contaminnates that can stick sliding mechanisms. You might have to bite the bullet and pull the oil pump. This is my opinion only. From what you describe it sounds like the oil pump has a priming issue, O ring, relief valve, excessive worn gears, leaky pump. But the fact you do the 3K rev to make oil pressure forcing it to prime is not normal. The oil guys claim most of engine wear is from the time it starts until it reaches operating temperature, that is conserning. I wish I had an easy fix but I don't have one except to pull the oil pan and start exploring if the oil tricks don't work.