Oil pressure drop! is it the pump?

[jmalaney]

As it turns out I guess I had a faulty gauge. I went to the local parts house, and purchased a $25 nice chrome manual gauge. I installed mine just behind the distributor cap, drilled a small hole in the firewall behind the dash, and mounted the new gauge on the bottom of the dash in plain view. I still had 40 - 60 psi while running down the highway and over 20 at idle. However, even with my old oem dash gauge unhooked it still is giving me a read of 20 psi on start and dropping down to 0 after about 5 minutes. I can't figure out how to make it stop but my oil pressure is fine. You can also take the oil cap off and look inside the valve cover with a light to see if you see oil being pumped but a manual gauge is the only true way to know what your pressure is.

Hope this helps.

Jason

[72 rs]

my 87 has 224,000 plus miles on it and my psi stays at 55-60 psi at all times -hot....cold....thicker oil....thinner oil it dosent make a diff. , and its been like this for 4 1/2 years ( as long as ive owned the truck).

[mbumgua]

Your 89 has a sending unit behind the distributer for the computer. It has another one for the gauge on the drivers side at the rear of the engine above the oil filter behind the exhaust manifold. It usually has a black cage or heat sheild covering it. I have replaced these on several of my 88 chevy trucks.

[liftgate]

j-ri is most likly correct. the press. relief valve is
probably stuck. try 3qts. of rizlone with 2qts. of
5w30. run it at a high idle (1800rpm) & block the
radiator with cardboard to warm it up to 210deg.
NO HOTTER. Remove the cardboard while it is
still running & bring it down to normal temp.
You may need to do it several times. If you
keep an eye on the guage you MAY see the
valve un-stick. Change the oil using 5qts.
If that doesn't work you'll have to remove the
pump & either fix the valve (part of the pump)
or replace the pump. While you have it apart
ck the screen, it may be clogged causing your
problem. Either way replace both, they're
real cheap when you are lying on your back.
please post back & let us know how you
made out.

[jdr2008]

I may be a little late on this one, I have an 89 K1500, Im the original owner, about 10 years ago I was having the same problem with my oil pressure, when it was cold it was ok, as it warmed up it would drop, and if I come to a stop it would drop to zero, Thought it was the oil pump, so I went and bought one and got everything ready, dropped the oil pan and guess what was in the bottom of it, the oil pickup tube, needless to say I was pissed, anyway I went ahead and installed the new pump with a new (oil pickup), but that was causing my problem, and I havent had any more problems with it, with no pickup in the pump it will still be able to pump oil and give you pressure but as it warms up and you move or stop, the oil will move about in the pan and the pressure will drop. you may have the same problem.

[Cadillakin'98]

I believe oil pressure should be @ 60 psi when you start the motor (cold). I want to add something kinda off topic right here.....when I start my truck up, I watch my oil pressure gauge AND WILL NOT drive until my oil pressure drops down to about 45 (atleast). When the motor is at normal operating tempreture, I belive oil pressure should be @ 30 psi and should never go below this. Now, it is normal for the oil pressure to rise as you accelerate and will range anywhere from 30 to 60 psi depending on the RPM's your running at. Now when you start to slow down, say for a light, pressure should begin to drop as the RPMs are decreasing. Thus at a red light, should read 30psi.
This is to my understanding. If I'm wrong, please correct me so that I may learn something as well. But, if I'm right, this should be the normal behavior of oil pressure, As for what I was noting "kinda off topic", waiting for motor to warm up when you first start it until your oil pressure guage to drop down atleast 15 psi is VERY crucial to your engine life and the need for premature maintenance. By no means should you ever start it up, pop it in gear, and go. I understand people are in a hurry first thing in the mornings but how about waking up 10 min later to let your mode of transportation that you rely on "wake up" as well?? If your running late already, whats 5 or 10 more minutes??

[mbumgua]

GM says 10 pounds of pressure per 1000 rpm is sufficient for a chevy 350.

[Cadillakin'98]

do u know what itsays about a 262(?) aka 4.3 v6?

[mbumgua]

A 4.3 is a 350 with two cylinders chopped off -10 pounds per 1000 rpm would be sufficient for it. Also 72 rs you probably need a new sending unit for your truck if you have never repaced it. What you said about the pressure always being the same is generally a sign that the sending unit has gone kaput.

[94bigblazer]

"A 4.3 is a 350 with two cylinders chopped off" haha, i never get tired of hearing that phrase.