Actually before I go through the trouble of replacing the oil pump.

Recently my C5 with a ported oil pump reads really low pressure esp after driving for a while.

No shavings in the oil, no noises or sounds, the oil temps get pretty high to me though verified its about right 267 oil temp on a 99 degree day 208 was the ECT.

As long as the car sits for a while. I go crank it up. Oil pressure 36-39 at idle. I drive say cruising 2500 rpms 40-43psi. As the engine warms up and the oil temp warms up. It goes down slowly cruising the same RPMs into the mid 20s then idling at around 15psi at 880ish RPM.

Its like its fine when oil has drained down to the pan but when it gets up into the top, its not filtering back down. Because of the initial normal pressure I assume the pickup tube is not clogged. Mobil 1 is used I have 10w40 in there now. Because of this issue. My plan is to swap the oil pump week after next. If anyone has any insight on this please let me know. Oh yeah and I replaced the sending unit behind the intake this weekend. Same readings come about. I use the style with the spacer between the electronics.

 

i noticed this on my vette also, so i purchased a autometer oil pressure gauge. factory gauge is wrong. i used the port under the alternator.

 

If it's a 2000 or newer I'd pull the lower oil pan cover(takes 10 minutes once oil is drained) and look at the pickup tube screen

ported oil pump? shimmed? gotta be some other details in the motor?

 

Its a ported pump from TSP. Its a 1997. The weird thing is when i first start up my pressure is fine. I watched a shop pull the oil pump/pan from my Z28 LS1 that was a nightmare. The vette looks like a much easier job. I dont want to mess with it if its not the problem. I have heard of the sensors being bad out of the box but since both read the same... I doubt its the sensor this time. The last time the sensor went bad it would just goto Zero if under 3000 rpms then 4000 rpms.... this one works for like the first few minutes of running. I post here because just like above usually my problem was someone else's problem...lol.

 

Since oil pressure is good on cold start I have my doubts its the pump. How many miles on the car? What filter are you running?

The motor may just be getting tired and loose, and with oil that hot, the pressure is down. If its a modified motor, something may be wearing quicker.

 

About 17k on the TSP stroker. NO nitrous so far.

 

I agree with tom01ss, check the pressure with a known good mechanical gauge before going further.

 

Well, my car was doing the EXACT same thing. I even made a thread about it awhile back..But I JUST got mine a month ago. Was going to go ahead and change the oil pump when i decided to just do it in a few months when I am able to get my bike. till then I went ahead and chaned the oil. Well...have to say my problem is GONE! Seems the dealer who had the car HAD changed the oil yes..but there was a cheap **** filter on there and even though th eoil was clean when I first checked, I believe he did NOT have full synthtic in it.

Here's what i did..

Went to the parts store, and got some valve medic. Poored that in the engine about three days or so BEFORE i changed the oil..let her have some time to get the crap out of the engine. Doing so for only 3 days has turned good clear oil to dark black oil! I know..I drained it. So good news is all the crap that was in the oil WAS in my engine.. Now its not. Then I changed the oil with full syntec, whats listed on the cap ..not 10w30 or anything like that..but what she actually called for. then of course a good high quality filter, not cheap crap. And now..she idle's at 30psi! And as soon as I give her ANY gas she runs all the way up to 55psi or so..no matter how warm she is or how long I have been driving her. BTW, my engine..she's JUST broken in at only 190k now..Everyone was telling me the same as you..and worse, engine rebuild time...now, she runs just as great as always and the oil pressure works as it should. No more oil pump worries! Good luck!

 

OK I dont mind doing that. Just hit the parts store I assume and I read there is a port behind the alternator? If someone could verify this I can stop by autozone or advance or orileys before I get back to the car.
This started shortly after I changed the oil. I put 5w20 in there mobile 1 synthetic. I have dropped that oil but not the filter this second time and put thicker oil in. The current filter probably had 60 miles on it. I dont know what filter I used I know it was from walmart. I have never heard of valve magic but I can ask for it. I was told to get some mystery oil would that work the same I know they have that mystery oil at autozone.

Guys thanks for all of your recommendations. Like I mentioned earlier most of my problems have already been had by SOMEBODY....

If I can install the guage easily I will definitely do that if the pressure shows good then I know that NEW sensor is bad. After this I will try the oil flush again and definitely a new filter.

Also could the fact that my oil dip stick is not mounted and slides up and down cause enough of a vacuum leak that it causes it to drop? I am looking for a dipstick and tube for my vette as we speak. It seems GM doesnt make them anymore or something because the parts places I usually use dont carry the part number I have for the stick. Which I am not sure is from a 6.0 or not. I had no engine in my car for years and then I put a TSP stroker and who knows what stick is in there. I know it reads hella high when I change the oil so im thinking its from a truck.

 

Oil dipstick would not cause an issue like your having.

It's Valve MEDIC..Avalible at most parts stores. Not valve magic..

As far as wal mart..Do NOT get a filter there buddy. Odd's are you got some cheap crap deal that's already clogged...Get a Mobil 1 filter or otherwise good quality filter. Basically have the guy at the parts store hand you the cheapest one he has, and a mobil 1 filter and you will FEEL the difference in weight! that's quality..no paper cardboard end caps there for ya.. then go back to the oil thats supposed to be used in your car..not something thicker. you CAN get OIL from wal mart..nut please, do yoruself a favor and use auto parts stores to get parts not wal mart.

 

If the problem started shortly after changing the oil, then yes, definitely do another oil and filter change. Get a quality filter this time, and see if the problem persists. I have heard the napa/wix filters are very good also.

 

OK update. I used the valve medic. Idled for about 10 minutes. Changed the oil (no shavings but boy did some golden brown oil turn dark brown. 10w30 Mobile 1 synthetic (what I always use) then added mystery oil. I let it idle for about 10 minutes but from the instructions I will need to drive it for 150-200 miles then change again. I havent had time to do that yet. So I cant tell if this will work.

The next thing I want to do in the near future is to install a manual guage. If someone could point me where to screw the gauge in on this block with a pic would be GREAT!!

Ill update later in the week when I get a few miles on the car. Idling is still on the lower side so I know its not fixed yet. After the guage install the pan is coming down for the pickup tube... after that a new ported pump will be ordered.

 

What filter did you install during this last round of changing oil?

 

BOSCH 7 bux at autozone. I didnt get the WIX the last one was an AC Delco. Honestly I doubt its my filter. Even the AC Delco should not have pressure that low.

I drove today with the mystery oil in there. at first an all time high in pressure. 43ish at idle and up to 58psi driving around 2500rpms. After about 15 minutes it started to drop and dropped all the way down to 14-17psi.

New oil pan pickup tube, and tsp's ported pump were installed with the engine.

I did some reading and it appears I will have to yank that intake again and put the manual gauge where the sensor is. My question is wont the car read zero pressure without the sensor in there? And wont the computer shut down at that point?

 

No you don't, as others have suggested, there is a screw in plug in the left /front part of the block, below the alternator. I believe it is the same thread as the oil pressure sensor under the intake. I know you don't want to throw parts at the problem, but throwing oil additives at the problem, is not going to do anything.....except overfill your crankcase....

http://forums.corvetteforum.com/1558574892-post59.html

 

The oil filter is NOT the problem. Every Chevrolet built since the 1960's has something called an oil filter bypass. It's purpose is to allow oil to bypass the filter when the restriction in the filter is too high. This can be due to a clogged filter - cold oil etc. etc. Even if the filter were completely plugged - the engine would have oil pressure (after all dirty oil is better than no oil).

The service manual does not mention an oil pressure test port - GM tells their techs to remove the filter - and use a special tool that screws on the engine in place of the filter and has a port in it that allows oil pressure measurement.

 

Thanks thats JUST what I was looking for I am about to go grab a manual gauge now and try it.

 

Ok sorry buddy, not been on for awhile..

Here's the deal. The better oil filter is NOT for better flow, its simply a BETTER filter. Get's more dirt out, and has a METAL end cap instead of some kind of crap cardboard one...

Now, as for your temp oil pressure boost, thats because the oil passages are not fully cleaned out yet. BUT are getting there. You left the valve medic in there for not nearly long enough! Go back up to the store..get another can. throw it in there and drive it for around a week! NO shorter, no longer.. THEN change the oil and I promise you the oil pressure will be up! At idle you should see around 25-28psi. Your car is doing the EXACT same thing mine did, because i did the EXACT same thing you did. And this time, do NOT put in any other additive till AFTER you see how this is going to work. Only AFTER seeing that this has fixed your engine oil pressure problems should you even consider the additive. Like i said before, it ADDS to whatever is there already, so basically all you did was to pick off some of the crap, but then go straight back with something that builds up on whats left! You need to get it ALL OFF before thinking of going back and doing that.. Good luck!

 

So you are suggesting, that a motor with 17k miles, has clogged oil passages?

 

OK guys. I havent done another round of valve medic yet. I havent done the gauge because the threads on the guages I can find around here are different. I dont have a way to tap a fitting. Is there a guage I can order that will screw right into that bolt with the torx head behind the alternator? Any link to one would be appreciated. Everything I find consists of tapping the oil pressure sending unit. Which I have an extra one to tap but im pretty sure my car would shut off without it plugged up no?
Update probably another 70 miles driven.
Oil pressure at first startup cold engine is now around 46 at idle..62ish at around 3500 rpms.
Still no knock no sounds.
After driving around 10-15 minutes. Pressure at idle 13psi I have seen 10 at LONG idle. I gave it a little throttle to get it back to 17 when I saw that... when it gets like this the idle is there and then its about 26psi at 2200 rpms.

The main thing is a way to tap that hole behind the alternator at this point. Then open up the front and drop the oil pan.