FueledSoul

iTrader: (18)

My oil PSI is about 30 to 35 when the car is frist started up the car idle is around 900rpms and once it starts getting warm it drops to 600rpms and the oil is about 10psi at idle. heres a video below.
anyone have an idea whats going on?

jv9999

iTrader: (1)

Assuming the gauge is accurate (probably not...), it means your bearings are getting loose. Not really a big problem yet. When it's 5 psi or less at a hot idle, it's time to to tear it down.

FueledSoul

iTrader: (18)

you sure?

FueledSoul

iTrader: (18)

could it be a oil sending unit? anything else that could cuase this
?

kens86

i had this problem twice before. what oil filter are you using? i had a fram sure grip. they are junk. i would maybe try a filter first.

fleetmgr

First thing is to put a real gauge on it. Dash gauges are notoriously inaccurate. If a mechanical gauge shows the same thing, I'd agee that the bearings are about done.

RED_DRAGON_85

your oil pump is engine driven.
if the RPMs are lower once it warms up, guess what, the pump is pumping less oil.
if you rev the engine back up to 900 it should go back to where it was, minus a few PSI.
the oil pressure will always be less on a hot engine because the oil's viscosity changes with temperature.

edit:
ok, just watched your video.
i didnt realize how much you would have to rev it to get the oil pressure back up.
mine has a high volume pump and a few hundred rpms will change the pressure by a lot more than yours.
i still think its the oil, but you might be due for a rebuild

IROCtheThird

iTrader: (15)

My gauge does the same thing, it did it with the old 305, I just put a fresh 355 in it and the gauge does the same thing, it will shoot up to almost 60psi on cold starts and once it warms up it stays at 30ish and at idle it drops down to right around the first line, so I assume its my gauge.

FueledSoul

iTrader: (18)

So iv been thinking about this would running a longer smaller gauge wire cause a problem like this?

8t2 z-chev

longer,smaller gauge wire would not matter-there is only
a few milliamps of current going to the gauge,cluster
does need a good ground for accurate readings though.
i would verify that the oil gauge is accurate with a mech.
oil gauge,i've heard 10 psi per 1000 rpm is ok oil press
my '69 camaro used to have about 5 psi oil press at
hot idle in gear(had worn cam bearings+oil pump)
never had any problems

FueledSoul

iTrader: (18)

how about swapping out gauges clusters? i swapped from a 115 to 145.

FueledSoul

iTrader: (18)

?

scooter500

iTrader: (1)

Heated oil will make less pressure. I tried various grades and now use castrol syntec blend 5/30; car starts @ ~45 and drops to 30's when heated. before full synthetic 5/30 gave me numbers like yours.

FueledSoul

iTrader: (18)

hmmm might have to try that. but im trying to pin point the problem. would swapping in a different cluster be? i went from a 115mph cluster to a 145mph cluster, i changed the wiring. engine was out of the car got a new oil pan and a 360* rubber gasket. i also cleaned the oil pump, added rear pan baffle and crank scraper torqued everything to specs, i put on a micron filter i normally run pure1's before any of this happned the oil PSI read over 25 / 30 idle. car doesnt leak at all so just trying to think or see what it might be

ploegi

Your best bet, and the ONLY way to be sure, is to screw in a mechanical gauge, and see what it has to say.

I don't think there are any differences in the oil pressure gauges between clusters. (other than the difference between an idiot light, or a gauge......)

Robb Knight

I had a similar problem for awhile and just recently fixed it. It ended up being the Oil Pressure Switch. It was giving me a bad reading on my Oil Pressure. It started out doing what yours does, but over time the pressure would give me lower readings until one day it would drop to zero whenever I wasnt pressing the gas. This lasted a day or two until it completely went. Then it would be at 30 when the car was cool. After about driving for 15 minutes it would drop to zero and no matter what not move unless I was doing like 120mph. I knew the car was still getting pressure so it was the pump. I did some research asked some questions on here and I found it was the oil pressure switch. On my car 350TPI Firebird Formula its located above the Oil Filter. Changed the oil/ filter/ and the Oil Pressure Switch (I believe thats what its called) and the pressure reading was back to normal. The part was only like 35$ if I remember correctly.

matthufham

iTrader: (5)

not to scare you but my old motor really did have that oil pressure, and i burned the rod bearings twice and burned the main bearings before i had to scrap the motor. i assume the oil pump was bad.

FueledSoul

iTrader: (18)

?

t-top havoc

iTrader: (3)

FueledSoul- IDK if swapping gauge clusters would lead to the low pressure reading.

That's your main question for now??--swapped cluster cause the low pressure reading??

FueledSoul

iTrader: (18)

im just trying to pin point the problem if you read the above you can see all that was done simultaneously before that i had 25 / 30 idle psi

ploegi

Have you put a mechanical gauge on it yet?

t-top havoc

iTrader: (3)

Can you plug into the 1st cluster and compare?
Also, I would do as ploegi mentioned.

FueledSoul

iTrader: (18)

the cars stored for winter. im going to have to pick up a mechanical gauge i know this is going to be the only way to tell for sure whats going on but man this is driving me nuts

92RS_Ttop

iTrader: (3)

My GMC truck was doing the exact same thing. Turned out to be the main bearings were almost gone and needed to be replaced. Just got the engine back in the truck a couple weeks ago actually. Definitely try a mechanical gauge, its the only way to check your Oil Pressure Switch accurately. Swapping gauge clusters should not affect it as the gauges are the same between all the clusters. The only way a cluster swap would affect it is if you put in a cluster with a bad gauge.

You said you had the bottom of the engine opened up earlier, so that brings to mind a few things:

Did you check the clearance between the oil pump gears and between the gears and the base plate?

How much gunk did you clean out of the oil pump housing?

Did you replace the nylon shaft sleeve or reuse the old one?

Did you replace the pressure bypass spring in the pump's base plate?

Did you replace the gears in the oil pump?

Is the pickup screen at the proper depth(ie is the new rubber gasket thicker than your old one thus putting the bottom of the pan slightly farther away from the pump pickup)?

FueledSoul

iTrader: (18)

Can i get a good reading using a oil pump primmer to turn the pump and then check it with a mechanical gauge?

92RS_Ttop

iTrader: (3)

Should be able to. As long as you are using a drill capable of high enough rpm.

FueledSoul

iTrader: (18)

So i bought a mechanical gauge and oil pump primmer. the drill i was using is adjustable from 0 to 550rpms. i had it set to as high as the **** would turn with the drag on the drill from turing the oil pump id bet it was was turing under 500rpms but at that speed the gauge was showing a constant 13psi. i didn't have a high speed drill handy at the time. i don't know what that that means but . . .


500 rpms got me 13psi

AlkyIROC

Camshaft turns at 1/2 the crankshaft speed so a drill turning at 500 rpm would be an engine running at 1000 rpm.

FueledSoul

iTrader: (18)

i did this in 25 degree weather im sure the engine it self and oil where much much colder.... what a disappoint

92RS_Ttop

iTrader: (3)

Yeah, that's not good. Have you tried changing the filter? If its clogged the bypass will open and your pressure can drop. The only other choices would be a new oil pump or a rebuild.

Personally, I would pull the pan off and remove a few rod bearing caps and #4 main bearing cap and check the bearings for wear/scoring. If they look ok, then replace/rebuild the oil pump and check your pressure again.