Oil Pressure Problem!!!

90lxracer · 05-04-2003, 07:58 PM

Here it goes. Whenever i forst start my car my oil pressure readings are normal. After I drive it for about 20 minutes, everytime i stop and let the car idle the oil pressure bounces from 0 back to normal. Then whenever i raise the rpm's...the oil pressure stays up. What could be my problem????

RoadWarrior · 05-04-2003, 08:16 PM

It might just be your sender. I know ive talked to a few people who have had them go bad on them. That would be my first try.

aar0s · 05-04-2003, 08:41 PM

i havent looked at mine in a while but i think that you can hit it with a little sandpaper and clean it . what kind of oil filter do you use?

Sicy Stang · 05-04-2003, 09:25 PM

Quote:

Originally posted by 90lxracer
Here it goes. Whenever i forst start my car my oil pressure readings are normal. After I drive it for about 20 minutes, everytime i stop and let the car idle the oil pressure bounces from 0 back to normal. Then whenever i raise the rpm's...the oil pressure stays up. What could be my problem????

Mine is the same way. Is it stock? It just sits there at 0 when I'm at a stop/idle.. then when I start driving it raises again.

I thought maybe it was just the shitty gauge. I know I've changed the sending unit a few years ago.

What do you do with the sandpaper?

RoadWarrior · 05-05-2003, 12:28 AM

I use a Canadian tire formula 1 filter. Im assuming you would use the sandpaper to clean the contact where the wire goes to the sending unit. Sometimes the unit itself will start to read wrong. The only other possibility is if its only doing it when the engine is idling then you may really have low oil pressure and its just not reading much so it goes down to 0. What does it go to when you bring the rpms up. Usually you should check the oil pressure at about 2000 but it should never be below about 7psi

90lxracer · 05-05-2003, 09:06 PM

My first guess was the sending unit also. I just installed a high volume oil pump about 100 miles ago and didnt change out the sending unit. the rpm's go up as the throttle goes up. Around 2000 rpm's it goes up to the middle notch (im guessing around 50 or 60?) but it wont go up above that too much. Thanx for all the help!

horsesnake95 · 05-06-2003, 01:01 AM

Well my first thought would be too hook a mechanical gauge up to where the sending unit screws into the block and see what your pressure is. I just went through this with my 95 GTS and was hoping it was just the sending unit only to find out that it was not that but the fact that I have 164,000 very hard miles on the motor and the main bearings are pretty much shot. Best of luck to you.

Chevyguy · 05-06-2003, 08:18 AM

Low oil pressure means excessive clearence between the bearings and crank. When the motor heats up the clearence expands and the oil viscosity drops. This is not a good thing.

As for the gauge, there is a diaphram and a spring, the oil pressure forces the diaphram back this gives the voltage reading which is converted to PSI (sort of) The sender unit can get crapped up internally and give erratic readings.

Bouncing readings sound like a crappy sender to me, get a new one on there first.

The stock gauge is pretty good actually, most dont want to face the fact the engine needs a rebuild!!

My car reads 70 - 75 PSI cold. 50-55 psi while driving hot, 10- 20 psi at idle ( Very bottom of N) so I know the bearings are getting kinda thin at 150,000 miles.

My beat up 305 in my Chevy has a reground crank and new bearings and oil pump. Even when fully hot still gets over 40 psi idling in drive.

05-04-2003, 07:58 PM	#1
90lxracer Registered Member Join Date: Oct 2002 Location: houston, Texas Posts: 65	Oil Pressure Problem!!! Here it goes. Whenever i forst start my car my oil pressure readings are normal. After I drive it for about 20 minutes, everytime i stop and let the car idle the oil pressure bounces from 0 back to normal. Then whenever i raise the rpm's...the oil pressure stays up. What could be my problem???? __________________ 1990 lx 5.0L 5 spd. BBk Lt's/BBK o/r x-pipe/2 chamber flows/holley systemax upper intake/holley systemax lower intake/holley systemax heads/Lunati cam/timing chain/fms 1.6 rr's/ pro-m 80mm mass air/ 24# injectors/ 190lbh./fuel pressure regulator/BBK 70mm tb/BBK 70mm egr spcr/fms 3.73 gear/Fluidyne Aluminum Radiator/Ford Racing Water pump/Underdrive pulleys 1997 Chevy Silverado Z71 4x4 6'' Pro-comp triple shock lift / 35x12.5 Pro-comp x-terrains on 15x10 welds / 4.56 gear / hypertech power programmer / Flowmaster 40 series exhaust / 2 12'' Audiobahn subs powered by houston acoustic 900 watt amp / white face gauges

05-04-2003, 08:16 PM	#2
RoadWarrior Registered Member Join Date: Apr 2000 Location: Edmonton,Alberta,Canada Posts: 317	It might just be your sender. I know ive talked to a few people who have had them go bad on them. That would be my first try. __________________ Fast Company

05-04-2003, 08:41 PM	#3
aar0s Registered Member Join Date: Nov 1998 Location: southern Illinois Posts: 312	i havent looked at mine in a while but i think that you can hit it with a little sandpaper and clean it . what kind of oil filter do you use? __________________ 88 gt convertable =-= cobra intake, accufab 65 mm tb headers alum underdrives steeda alum.lca's, springs, c/c plates kyb struts 230 hp to da wheels http://www.cybersteed.freeservers.com

05-05-2003, 12:28 AM	#5
RoadWarrior Registered Member Join Date: Apr 2000 Location: Edmonton,Alberta,Canada Posts: 317	I use a Canadian tire formula 1 filter. Im assuming you would use the sandpaper to clean the contact where the wire goes to the sending unit. Sometimes the unit itself will start to read wrong. The only other possibility is if its only doing it when the engine is idling then you may really have low oil pressure and its just not reading much so it goes down to 0. What does it go to when you bring the rpms up. Usually you should check the oil pressure at about 2000 but it should never be below about 7psi __________________ Fast Company

05-05-2003, 09:06 PM	#6
90lxracer Registered Member Join Date: Oct 2002 Location: houston, Texas Posts: 65	My first guess was the sending unit also. I just installed a high volume oil pump about 100 miles ago and didnt change out the sending unit. the rpm's go up as the throttle goes up. Around 2000 rpm's it goes up to the middle notch (im guessing around 50 or 60?) but it wont go up above that too much. Thanx for all the help! __________________ 1990 lx 5.0L 5 spd. BBk Lt's/BBK o/r x-pipe/2 chamber flows/holley systemax upper intake/holley systemax lower intake/holley systemax heads/Lunati cam/timing chain/fms 1.6 rr's/ pro-m 80mm mass air/ 24# injectors/ 190lbh./fuel pressure regulator/BBK 70mm tb/BBK 70mm egr spcr/fms 3.73 gear/Fluidyne Aluminum Radiator/Ford Racing Water pump/Underdrive pulleys 1997 Chevy Silverado Z71 4x4 6'' Pro-comp triple shock lift / 35x12.5 Pro-comp x-terrains on 15x10 welds / 4.56 gear / hypertech power programmer / Flowmaster 40 series exhaust / 2 12'' Audiobahn subs powered by houston acoustic 900 watt amp / white face gauges

05-06-2003, 01:01 AM	#7
horsesnake95 Registered Member Join Date: Oct 2002 Location: illinois Posts: 26	Well my first thought would be too hook a mechanical gauge up to where the sending unit screws into the block and see what your pressure is. I just went through this with my 95 GTS and was hoping it was just the sending unit only to find out that it was not that but the fact that I have 164,000 very hard miles on the motor and the main bearings are pretty much shot. Best of luck to you.

05-06-2003, 08:18 AM	#8
Chevyguy Backyard Mechanic/Chemist Join Date: Feb 2001 Location: Acton MA USA Posts: 435	Low oil pressure means excessive clearence between the bearings and crank. When the motor heats up the clearence expands and the oil viscosity drops. This is not a good thing. As for the gauge, there is a diaphram and a spring, the oil pressure forces the diaphram back this gives the voltage reading which is converted to PSI (sort of) The sender unit can get crapped up internally and give erratic readings. Bouncing readings sound like a crappy sender to me, get a new one on there first. The stock gauge is pretty good actually, most dont want to face the fact the engine needs a rebuild!! My car reads 70 - 75 PSI cold. 50-55 psi while driving hot, 10- 20 psi at idle ( Very bottom of N) so I know the bearings are getting kinda thin at 150,000 miles. My beat up 305 in my Chevy has a reground crank and new bearings and oil pump. Even when fully hot still gets over 40 psi idling in drive. __________________ 2001 Crown Vic Maurader Airbox/MAF, DR chip Edel IAS shocks Single exhaust :wtf: 93 P-71 Vic interceptor Backup car now 90 5.0 LX Notch SOLD 74 Chevy Laguna type S-3 454 under construction Currently apart undergoing bodywork.

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