Oil Pressure Dropping When Engine is Heated

[Matt G]

This just started happening this week and it has me worried now... When my car starts and it is cold I have no problems with the oil pressure.. at idle it stays at 30 and during acceleration it goes up to 60.

But as the motor heats up the oil pressure goes down during acceleration. When my car is fully heated the oil pressure stays at a constant 34-40. Whats wrong with my car??

Could it be from increasing the timing of my car with my HP Tuner? I am going to re-load the stock tune to see if it helps.

[98Camaro3.8]

I don't know the answer, but it's not abnormal for oil pressure to drop once it's warmed up. It thins out and becomes easier to pump, so pressure drops. Should still stay at the required 60 psi during driving, though.

Changing the timing with HP Tuners will have no effect on this. Gotta be something mechanical.

What type/weight of oil are you using?

[Matt G]

10w30.. what it says on my oil cap.. btw i checked oil level and it is okay


Also.. before this week it has never given me this problem. I am going to have my brother take a look at it and see if he can figure out whats wrong with it tomorrow.

I have been babying it.. keeping it below 3k rpms until I can have it checked out. What kind of damage could come from driving it while it is below 60 psi?

[ January 19, 2006, 07:18 PM: Message edited by: Matt G ]

[BobbyZ72]

do you change your the oil or does someone else? Sounds like the oil it too thin. As long as you have oil pressure, you shouldnt do any damage. Maybe the sending unit got clogged and is putting out wrong readings.

[Matt G]

I change my own oil every 3k miles... it was done approx. 2000 miles ago. I havn't changed anything about my oil when this started to happen.

Has anybody ever heard of oil pressure just dropping out of no where? What could this possibly be?

[Marty85]

Actually Matt im having the same problem. Over the past couple of months my oil pressure has seemed to steadily fall from where it used to run around 40 psi hot at about 1200+ rpm's and about 20 psi 700 idle, to about 37psi at 1200+ and 18psi at idle. And if I rev the motor over 4 grand like wide open throttle it goes down even worse seems like for a few minutes. Im starting to think ive got a bad sending unit because its so unstable it seems like and next oil change im going to put in 10-30 instead of 5-30 like I believe I put in this last oil change...thank goodness the next oil change is only 500 miles away.

And im like you worried to death about it. Im starting to think something is trying to let go in the bottom end like a rod bearing or crank bearing but it doesnt knock, tick or anything, even when its first started up.

['94 Camaro RS]

i dont have a problem with my 3.4 liter. when its cold outside and i first start it its around 60psi until it warms up to running temp then it stays around 30-40 psi. if i get on the highway it will go back up to 50-60 psi then once i get off it will drop to 20-30 psi.............from what i read from your original post the oil pressure drops under acceleration meaning your pump or sender unit is going bad.

[Marty85]

Well it doesnt really drop during acceleration but its nowhere near what it used to be when cruising. Used to sit at 40 psi at anything above 1200 rpm's and at 20 below that. Now its about 35-37 to 17 idle. Im really starting to think its my sending unit now however because I just got through driving my maro all over the place tonight through town and its acting normally as it once did. The only time min will actually read anywhere near 50 psi is when its cold.

[terminaldegree]

The 3800 series II motor is supposed to make at least 60psi at 2,000 rpms. Hopefully there's something wrong in the sender/sensor end of things. It's cheaper than the possible alternative...

There's NO way that 10w-30 is too thin and would cause that kind of change in pressure in our cars.

If it were mine, I'd stop driving the car NOW until it is diagnosed. Good luck.

[Marty85]

3800's usually do keep good oil pressure. I havent seen on yet that didnt hold 50-60psi oil pressure. 3400's are different however. Ive seen alot of them where the norm is 40-45 psi and 20-25psi idle.

[Loochy88]

Originally posted by Marty85:
3800's usually do keep good oil pressure. I havent seen on yet that didnt hold 50-60psi oil pressure. 3400's are different however. Ive seen alot of them where the norm is 40-45 psi and 20-25psi idle.

my 3.8 looses some pressure whenever it warms up a bit, but its really only noticable at idle. the lowest ive ever seen mine is the 1/4th mark on the gauge (hot summer days at idle).

[zlexiss]

I notice mine drop at idle when hot, especially road racing in the summer where I've got the car basically floored for 1/2 hour at a time in 95*+ heat.

Always comes right back up to 60 as soon as I give it any gas at all, so it doesn't worry me.

Aside from thinner oil when hot, anyone else with idle pressure drop using the oversize PF-52 filter? Wonder if reduced backpressure from the increased filter area contributes to this - if so, then you're still probably getting the volume flow you need, esp at idle.

[Matt G]

from what i read from your original post the oil pressure drops under acceleration meaning your pump or sender unit is going bad. [/QB]

So either my pump(please be specific as to what kind of pump) or sender unit(not sure what that is either) is going bad. My pressure dropped significantly within the past 2 weeks. I will explain it a little better then my orignal post.


At idle (warmed up) my oil pressure drops below the 1/4 mark.. a little bit.. not much. Then once it reaches 2k rpms the oil pressue only goes up to about 35-40 psi.

About 3-4 weeks ago I had no problem with my oil PSI. At idle it stayed at 30 PSI(1/4 mark). above 2k it stayed at 60 PSI(1/2 mark).

Does any one know how I can test the sender unit or pump to see which is giving me this problem?

[Matt G]

I went over to my brothers and had him check it out.. he told me its either a clogged oil filter or an oil pump. I bought an oil filter because its been about 2400 miles since I changed my oil and it sounds like the clogged oil filter might be it.

I will keep everyone posted.

[notsonic]

my oil pressure redlines when im idle after its hot.

havent had any problems [img]redface.gif[/img]

im sure i should so something about it but where would i begin [img]tongue.gif[/img]