Low oil pressure during idle

rzibilske77

Registered User
title expains it all
When the car ides the oil pressure drops very low and sets off the check gauges light?
when driving the pressure is norm with the need le pointing approx. staight up or a tad to the left.
any ideas it just started, new headgaskets last week, new cam sensor too
 
More than likely the wire that connects to oil sender is loose. This is a very common thing as the connections get corroded after time. Pull it off and clean it out along with the sender connection. That should solve the problem. The sender is located on the front behing the stupid bracket the goes from your power steering pump to the water pump.
 
First don't trust the guage/switch on board. Replace the sensor or plug in a real guage and verify..

Then.. if still shows a problem,

I had this problem on an earlier vehicle. You may not want to hear what I discovered...


I found the pressure relief spring was broken in the oil pump.. Replaced the oil pump and problem solved. but what a pain...
 
You didn't say if you changed the sender when you did the head gaskets. Or how many miles are on the odometer. Before doing the heads, how was the oil pressure then?
I would start by changing the sending unit.
Is your pressure normal when the engine is cold, drops as it warms up? If it does and how you discribe how it is "low" at idle, then returns to more normal readings at higher RPM's , then I would have to say the main bearings are showing some wear.
 
35th sc
94k
no new sending unit, actually all the gauges art acting a bit funny...the tach is not right seems to go down slower, i just changed out my dis module, but thinking the other was not bad.





Cobra85 said:
You didn't say if you changed the sender when you did the head gaskets. Or how many miles are on the odometer. Before doing the heads, how was the oil pressure then?
I would start by changing the sending unit.
Is your pressure normal when the engine is cold, drops as it warms up? If it does and how you discribe how it is "low" at idle, then returns to more normal readings at higher RPM's , then I would have to say the main bearings are showing some wear.
 
kpatton said:
First don't trust the guage/switch on board. Replace the sensor or plug in a real guage and verify..

Then.. if still shows a problem,

I had this problem on an earlier vehicle. You may not want to hear what I discovered...


I found the pressure relief spring was broken in the oil pump.. Replaced the oil pump and problem solved. but what a pain...

This is good advice. Get a mechanical gauge from AZ or wherever ($15) and mount it under the hood. If oil pressure is in fact dropping that low on idle, then you have issues. You can replace the oil pump with a high volume unit, and you can run heavier oil. I recommend 15w50 Mobil 1. My engine is abused regularly and has over 190K miles on it. It maintains 40psi hot idle oil pressure which gives me warm fuzzies. :)
 
keep in mind that the oil pressure gauge is based on voltage, so its not going to read 100% or be fully accurate, but if its dropping down to nothing, its probably the sensor itself, or a fray in the wiring somewhere or worse case, the pump
 
i believe u r correct as maybe a sensor or wire issue, because when it was doing this, the cars mechanical running condition did not change at all...still very strong...idle would still sit at 600 or so..normal, so i figure if it was truthfully that low it would idle rough and possibly die.





Fireman_In_A_SC said:
keep in mind that the oil pressure gauge is based on voltage, so its not going to read 100% or be fully accurate, but if its dropping down to nothing, its probably the sensor itself, or a fray in the wiring somewhere or worse case, the pump
 
You guys are cracking me up.

Yes, wiring and sensors give trouble.

However the bottom line is that if it is NOT a sensor, then every moment you continue to drive the car with low oil pressure is causing permanent damage. Is that worth the risk to you? Would you like to add your name to the list of people who said "yep, I was driving along one day and the rods just went....".

Because there is a long list of people who have said that very thing if you care to search the boards and find out. If as you say, the gauge drops at idle, that is a pretty darn strong indicator that there just might be a more serious problem than a loose wire.

And no, low oil pressure will not cause the motor to run rough or die. Well, maybe after the bearings spin it will run rough, but not necessarily and by then it is WAAAYYY too late. :)
 
The car is not being driving till i can find out whats going on for one, maybe you took it wrong that i don't care that it is doing this...its that i am hoping for the best.
Now what worse case scenerio that is wrong beside pump, sending unit..sensor etc...thats minor as far as i am concerned.









XR7 Dave said:
You guys are cracking me up.

Yes, wiring and sensors give trouble.

However the bottom line is that if it is NOT a sensor, then every moment you continue to drive the car with low oil pressure is causing permanent damage. Is that worth the risk to you? Would you like to add your name to the list of people who said "yep, I was driving along one day and the rods just went....".

Because there is a long list of people who have said that very thing if you care to search the boards and find out. If as you say, the gauge drops at idle, that is a pretty darn strong indicator that there just might be a more serious problem than a loose wire.

And no, low oil pressure will not cause the motor to run rough or die. Well, maybe after the bearings spin it will run rough, but not necessarily and by then it is WAAAYYY too late. :)
 
oil pressure readings

gauge reading

idle 25psi in park
idle 20psi in gear
2500 rpm 45-50 psi

sending unit looked fine, so is my pump on the way out or what my next move?
I hear alot about putting on the newer model pump on the older models...
I have a 90 so should i go with a 95..will it bolt right on?
thanks guys :)
 
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If my memory is correct, those readings seem to be about the same as what I get at idle, maybe a little lower at 2500rpm, but that could just be differences in the oil.

Get somebody to help you and sit in the car while you watch the real pressure gauge from the engine compartment. Now wiggle the wires and the sender around and they can see if the dash gauge drops out. If you see the real pressure gauge drop, cut the engine immediately of course...
 
Was the car completely warmed up? Idling will not get the oil up to operating temperature so if you hadn't driven the vehicle (I assume not) then oil pressure readings would drop lower after the car has been driven.

First thing I would recommend is to replace the oil with 20w50. If pressure comes up to 60-70 above 2000rpm, then your pressure relief valves are ok and the motor simply has excessive clearances. If pressure does not rise then oil pump relief valves may be suspect.

In either case, I'd seriously consider a high volume oil pump (melling M246) and the heavier weight oil. SC's are known for wearing out the bearings badly and the heavier oil will help.

For example, my engine with 190K+ miles on it pulls 35-40psi hot idle and 65psi hot cruise (above 2000rpm) with 15w50 oil in it. I would consider this minimum oil pressure for safety.
 
i did let the car warm up.....the oil pressure doesn't drop till the motor is good and warm and only in gear..if i put it in park idling will be 30 psi or so.
As for this new pump melling 246...where did i find this one, and will i have to make any adjustments?
Oil wise i have been using full synthetic mobile 1 10-40, so u think i should go to reg. 15-50...also i'm no expert here and you see my location is Houston and the temp are about 95 degrees avg..with tons humidity so with all consideration a heavier weight oil is what i need correct?
thanks for all info guys.

Btw....anyone know where i can get purple ice(coolant additive) made by royal purple, its amazing how the company is right down the road from me(5 miles) but can't seem to get ahold of this .....lol :)
 
You can get the pump from Summit and it bolts right in. Yes, I most definitely would switch to 15/50 regardless.

After you drive the car the oil will get hotter and oil pressure will drop further. For the check gauges light to come on it has to drop to about 11-15psi I believe which is completely possible after you've driven the car. For example, mine idles cold at almost 70psi.
 
Sorta on the same track here....possible oil pressure issues...

92 SC, 112k miles
5-30 oil, changed religiously every 3k miles.

Sometime in the past week, the oil pressure gauge needle has dropped, hot running or idle..makes no difference, from running between the R and the M in NORM to running between the O and the R. Again...makes no difference if at idle or at speed.

It has never varied since it was new....(Yes, I bought it new in '92).

So....reading the previous posts in this topic, I need to actually install a real gauge (test) and read what it says. I just did the head gaskets in November and ever since, the car has had a heating problem..(*That* is being discussed in another thread.)

I was just curious because I get no variation in pressure from cold to hot or low RPM to high...never have.

I am going to get the oil tested by BlackStone Labs....that will tell me the condition inside the engine.

Thoughts anyone?
 
Found my problem, it wasn't the pump, it was the crappy oil that was put in it after hg's job. Cheap oil that was so thin it was foaming..it poured out almost like water...no it wasn't water.
i put in new mobile 1 15-50 synthetic and no more issues with low pressure.
 
MCharlie said:
Sorta on the same track here....possible oil pressure issues...

92 SC, 112k miles
5-30 oil, changed religiously every 3k miles.

Sometime in the past week, the oil pressure gauge needle has dropped, hot running or idle..makes no difference, from running between the R and the M in NORM to running between the O and the R. Again...makes no difference if at idle or at speed.

Welp..Whatever the problem was, it is gone now. Oil pressure back up where it has always run.

Go figger!
 
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