Why does my oil pressure go down when the temperature goes up? the temp goes to like 220 and then the pressure will drop to 3 when i let go of the gas. yesterday the car turned off on me at a stop sign. Do i need another oil pump? My car is a 1989 RS with a rebuilt 305 tbi. This happens when the AC is on most of the time.

 

Oil thins out as it gets warmer, so.. the pressure will drop.

However, 3psi is wayyyyyyyyyyy too low for our engines. Something's wrong.

On the up side, if your engine hasn't seized yet, chances are it's NOT the pump, but rather the pressure sender. Either replace the sender, or buy a pressure gauge to check the validity of your dash-mounted oil pressure gauge.

------------------
89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

My pressure at idle is about 8-11. Lower than a lot of folks but the engine is still and will be going strong. I think the general rule is 10 psi for every 1000 rpm. Yours is rather low. I'd bet its the sender. Check it out.
bsa

 

RSS2K,

As Enkil points out, the viscosity of oils decreases as its temperature increases. This viscosity breakdown occurs a lot less with synthetic oils, and is just another reason to use them.

# PSIG is too low for adequate protection even at idle - unless you've retrofit a Briggs & Stratton splash oiler between the fenders. Your oil pressure gauge is the first suspect, as they are notoriously unreliable and inaccurate. Verify the actual oil pressure with a mechanical gauge connected in place of the oil pressure sending unit. If the mechanical gauge indicates something significantly different, replace the sending unit. If the mechanical gauge verifies the dash instrument, start shopping for gaskets, bearings, and a new oil pump at the least.

------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

check the sender first,but, my guess is that its been rebiult and the bearings are ****ed,please trust me on this one check the sender if thats it,... fine! but, then take off the oil pan if its not and take loose a few main caps...if they(the bearings) are screwed then so is the engine if its killed the bearings then the entire engine must be broke down and re-done top to bottom .even the distributor!!!

------------------
89 firebird formula


360 10:1compression (350 .060 over)/fully balnced and blueprinted
comp cams xe262 cam
performer rpm intake/port matched to heads
#1405edlebrock 600
sportsman 2 heads 64cc 2.02/1.60 valves 200cc intake runner/cnc pocket ported
msd 6al/msd8.5 super condutor wires
h.e.i. proform 50,000 volt vac. advance ditributor
700r-4 with 3.08 first gear and 3.23 posi 7 5/8 rear end.
b trans shift kit(will kill shifts...suck dong!!)
shorty heddman hedders with custom 3" pipe y-pipe back(no damn cat!) with 40 series flowmaster!
griffin daul1" core rad.cutom fabrication to fit(but no cutting )


future mods: 406 roller REALLY REALLY REALLY RADICAL!!!!!

 

Try making sure you have changed the oil recently, I am sure you have and also the type of oil is important. I am sure you already knew, but I had to mention it. I put a good bet on the oil sending unit being bad, but it could be the gauge as well. Also if the car has a electric sender the wire could be messed up, considering you have more of a problem with it when the air is on.




------------------
1987 Firebird Formula
305 LG-4
GM Vortec heads 2.02x1.6 valves
Crane CompuCam 2030
700-R4 Trans
4 barrel quadrajunk remained by holley (this carb stinks!!!)
edelbrock performer intake
Hypertech Thermomaster Chip
Open Element Air Filter
No Cat with Straight pipe (Dynomax muffler rusted apart and fell off probably could not stand the heat )
Accel H/P Coil

- Soon to be installed
383 stroker (built and ready)
NO MORE COMPUTER CRAP
700R4 Lockup kit
Edelbrock TES
True Dual exhaust or 4 inch single pipe to dual 2 1/4"
Stall convertor