I just got back from a 430 mile trip, 400 of those miles being nonstop and oil pressure is acting strange. I did not notice it until the trip back home. I was going a steady 75 MPH all the way around 2250 RPM and the pressure was reading 14-13 PSI and got as low as 10 PSI. Then a couple of times it jumped up to what you normally would expect the pressure to be for those RPM's, 20ish PSI. There are no awkward engine noises indicating a messed up bearing or anything like that. I drove it to school today and the pressure stayed just above the red on the freeway and plunged down to 5 PSI, which is halfway into the red, during idle in the city. So I picked up a new oil pressure sender unit from NAPA today and installed it only to see no difference. My next move is to put in a K&N oil filter which I know increases pressure, I have went with cheap regular filters the last two oil changes to save some coin, and add some Lucas Oil Stabalizer. If there are any clearance problems with the bearings I am hoping the stabilizer will help. Do you guys know of anything else that could be causing this problem besides what I've mentioned or a messed up oil pump/pickup tube. I have been having problems with the instrument panel as my voltage gauge mysteriously went out and I had to move around wiring to fix the temp gauge and the fuel guage halfway works (but I think its the sender in the tank), but maybe this is just writing on the wall. Any comments would be appreciated, thanks.

 

mine did that once so i changed the oil. Turns out i only had about 1-1.5 quarts in the whole damn thing. (needs about 5 w/ filter). after the oil change it read the correct pressure.

Good luck

 

I wish it was that. I changed the oil about a week ago for the trip and put in exactly 5 qts. and the car does not leak and hardly burns oil. I have been wondering if I got a messed up filter and it is causing a restriction.

 

Even though you changed the sender, I'd be suspicious of the reading. You might try a mechanical gauge.

 

Yea i have to say that sounds strangely similar to a car running with low oil and by similar i mean exactly lol. Now its possably like you said that youve been haveing problems with the instrument gauge it could be just a bad gauge. Also are your sure its the right weight oil and that you dont have any water mixing in the oil? Ide deffinetly check it with a mechanical guage but untill you figure out whats wrong the best piece of advise i could give you is...... STOP DRIVING IT! From experiance cars with low oil pressure will run quietly untill its far too late. Sadly no oil additive or oil filter will save you eather. I mean its possable maby you do just have a bad pump or a plugged pick up tube or even sludge built up you might be ok but if you run it like that damage beond repair will occure (if it hasnt already) and i can guarente it will sieze at the most inconvieniant moment possable. Ive seen cars run without oil and the bearing were fried to the point of knocking but the crank survived and it only needed one new rod simply because they stopped quickly. On the other hand ive seen motors run with the "i just gotta get it home" atitude with bearings split fractured into pieces (some gone all together) cranks wonr down to the point there visably out of spec cams ground down to nothing and cranks welded to rods due to the excessive heat and believe me thats not a bill you want to pay lol.

 

It cant be low oil I have checked that and re-checked that a million times. As far as coolant in the oil it did not look like it on the dipstick but I will look into it. My next step is to hook up a mechanical gauge to rule out the gauge on the instrument panel, which is right now what I suspect is the problem is. I mean the car drove 200 miles nonstop with supposed low oil pressure with out a hiccup. So I think something would of happened then. ????

 

This same thing happened to my car right before it spun a bearing and siezed up. I also had engine gunk built up like you would not believe. Once i pulled a valve cover off i could see why i was having the gauge act weird. Definatly try a mechanical gauge first though.

 

Yea you might be supprised how far motors will go with some problems. Some are worse than others but as long as theres some oil flowing things will be lubricated the better lubrication the longer it will go. Now because the motor works kinda on an "air hocky table effect" low oil pressure will cause things to make contact and will grind them down and you might not even hear it over the motor in the begging as the noise is being dampened by the fact there is some oil. To me its amazing how far a car can go even when everythings in good order just thinking of all thoes parts moving at 3 or 4 thousand rpms for hundreds of thousands of miles under 200 degree temps stressed with compressed explotions hitting the crank like hammer blows which shielded only by a thin layer of oil. Its really amazing when you think about it. So how long can you go befor youll notice something? Who knows it really depends on the the severity of the problem and what is causeing the problem. However even from reading your original post it dosnt sound good. You may not hear and knocking or feel a loss of power but originally when the problem started you had pressure that was all over the place but dropped as low as 10 PSI. Then later you said you drove it to school and you said that it just above the red and dropped as low as 5 PSI. Sounds to me like you oil pressure is getting worse which is an indication of the bearings getting thrashed and to for the oil pressure to drop that much in that short a period of time its at a pretty accelerated rate. Again it could always just be a bad guage or wireing which would be great but if its not that simple ever mile is one more nail in the coffin.

 

Sounds like you need a new oil pump. Cheap part....PITA to change.

I went through the same thing a couple of years ago, new sender, new gauge, fancy oil/filter.....but nothing changed until I swapped in the new pump.

 

I would expect a lot more PSI at that RPM. Spec is 30-55 PSI at approx. 2000 RPM. Both my '84 T/As run around 45 PSI past about 1500 RPM. I would hook up a mechanical PSI gauge and verify that the dash gauge is correct. If it really is that low, you are probably looking at a new oil pump at best or having to replace the crank and rod bearings.

 

Well I have yet to do anything to the car yet. It is starting to act normal now more than abnormal, which is confirming my belief that is is the gauge. If the instrument panel wasn't such a PITA to take off I would look into, but for right now I am going to keep an eye on it. I should double check it with a mechanical gauge, but hours at work just got cut and school books were expensive this semester. The Haynes manual says oil pressure should be a minimum of 15 PSI at 2200 RPM so right now I seem to be on the safe side of things.