soccer794

I'm not sure if this is a common thing, the way its supposed to be, or means that somethings messed up...when I first start the engine the oil pressure is very high, often topping out the gauge...after running for a while and getting up to temperature SOMETIMES...not sure if all the time or not just notice it when I happen to glance that way...but anyways sometimes the oil pressure will drop way down it will sit about a quarter of the way on the gauge when I'm driving and then when I come to a stoplight and idle the oil pressure will drop way down often to zero or at least close enough that it looks like its reading zero. I assume that this would contribute to some overheating, cause if I rev the engine up some and the oil pressure rises the temperature will start going down, or at least stop rising....any help appreciated.

kdf1986

I would like to see what responses you get, because I have the same problem on a 73 454. At startup the oil pressure gauge is in the upper 3/4 range. After about 30 minutes of driving the gauge will go to an estimated 5 psi if I can calculate the pressure divisions. Just a little north of 0. If I keep the revs at idle around 1000 rpm I can get 10-15psi at idle, when I am at stop lights.

I plan on replacing the oil pan soon, since it is dented, and then putting in a new oil pump to see if that fixes the problem.

I would like to see what responses you get for your problem.

kdf

Mr Fanuc

Same here.........I figured that the bearings are shot since my engine is very tired and needs rebuilding. I even put a new pump and sending unit on but still get the same thing. I hope to make it through the summer before pulling the engine.

1971corvette

why don't you all try a known good reading oil pressure gage,before tearing oil pans off,replacing oil pumps.I have noticed air bubbles in my oil pressure line,when I had the plastic line,I had always bleed out the air,and never had any issues.

I have a 1990 chevy van with 248 thousand miles,oil pressure was getting to about 10 lbs. at idle,I put some of that lucas oil additive in,now 30 lbs. pressure,this should get me by untill I replace the motor. If 7 dollars will make this thing last another few thosand miles I will be a happy camper.

Ybnormal

I just rebuilt my top end of my engine and put a new oil pump in while I was at it. I too had the same problem. I'm running 40 psi at start up and cruse speed, but once hot and at a stop light at idle I'm at 20 psi. The same as before the new oil pump. It is a combination of bearing wear and oil viscosity being thinner at operation temps. Try some 20-50 or straight 50 weight oil for summer high temp operations and it should increase your oil pressure when hot.

YBnormal...drive a vette

StickShiftCorvette

The symptoms described indicate worn rod bearings, main bearings, or lifter bores.

There are two ways to deal with the problem. You can rebuild the entire engine to specification, or you can adequately treat the problem by installing a high VOLUME oil pump. Changing the oil pan or pickup won't do a thing.

As long as there is no severe knocking your engine can be maintained with adequate oil pressure.

Volume is needed to make up for the more than designed for losses occurring in a worn engine.

As long as you have 10 psi at hot idle you should not suffer engine damage or accelerated bearing wear. If you have 35 psi at hot running speeds (over 1500 rpm by my tastes/experience) you should be fine - although I wouldn't lug (pull heavy load at low engine speeds) your engine between idle and 1500 RPM- in other words when you had less than 35 psi oil pressure.

2th farmer

I don't want to hijack but, what is a "normal" oil pressure thru the range of driving. One of my cars stays way right ALL the time (recent rebuild) One of my cars starts out good but, at operating temp and driving speeds falls to 35 psi.

StickShiftCorvette

If your car has the same oil pressure all of the time it means your oil pump has the volume required to keep the pump in relief ALL of the time. That just costs you some power - basically your system is dumping oil ALL of the time to sump. There is a valve in the pump that limits the pressure at the pump.

dwe

I understand the low oil preasure after warmed up due to wear in the engine but why would preasure be very high at cold start?

rihwoods

What oil you running ?? Heavier viscosity oil can increase pressure thru system....I read somewhere GM states having 40 PSI at 2000 RPM is ok....guess that is a benchmark....I have that with 120,000 miles on original engine...about 20 PSI at 1000 RPM (idle)...and 45-50 at cold start...
Rich

mandm1200

I don't know what you mean by very high. Oil pressure is typicall higher when the oil is not up to temperature. This is because it's thicker and does not flow as well. That's one of the reasons for running a littler thinner oil in the winter. Having more oil flow (volume) to the top of the engine is what's is needed.
Oil presusre is a measument of resistance to the flow. Using the same pump, the more flow the lower the pressure. When the oil pressure drops it means more oil is flowing out of something like rod/crank bearings.

dwe

Thanks for the reply. It seems that a number of us are having the oil preasure reading very high when the engine is cold. In my case the reading drops to normal when things warm up. Just wondering if this could be the guage, sending unit , a normal situation or something scary. Your response has givien me the idea to try experimenting with thinner oil to see if there is any effect.

79 vette

I heard somewhere that 10psi per 1000rpm is ok usually oil idiot lights dont come on unless it drops to 3 psi

rihwoods

soccer794...????????

grybdn

mine reads about 17 at idle, 35 while driving at normal speeds 75mph

Techno

The engine cooling when you increase the rpm isn't the oil but airflow past the radiator, thats what that funny wax vacuum switch does on AC cars

vttedrm

My Stingray's oil gauge reads zero when the car is off and it's off the scale when it's running. It doesn't matter if it's hot or cold, it's maxed out while the car runs. It does have a high volume oil pump (according to the last owner) if that makes a difference.

My 442 reads between 40-60 when operating normally. If it reads lower than that, then I know to add oil.

Perhaps the first thing to do is to check your oil level. Then go on to the next probable cause.

memLT-1

Ditto on my 72 LT-1.Running 20w-50w Castrol

RC73

I belive between 30-60 when operating is safe with 35-40 being the norm. Mine never falls below 30 or goes above 60. Gauge goes up to 70 or 75 psi on my 73.

7d2 vette

if the pressure is to high its called bearing wash not lubricated and thats no good ethier so dont chase them high numbers if your worried go to full synthetic oil it will gain you 10 psi and hold higher pressure longer my2cents