2003 Intrepid: Oil pressure light comes on as engine warms up


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Old 11-04-09, 11:48 PM
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2003 Intrepid: Oil pressure light comes on as engine warms up

I took my car in for it's regular oil change. Beginning exactly since that time, after the engine has been running for about 7 or 8 minutes, the oil pressure light comes on when the car idles at a traffic light.

The oil pressure light goes out when the engine revs are high enough.

Before the engine gets too hot, keeping the revs at about 1000 rpm is enough to keep the light off.

But as it gets hotter, the revs have to be kept at 1500 to keep the oil pressure light off.

Ideas? Bad oil? Bad oil filter?

Thanks
Greg
 
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Old 11-05-09, 04:45 AM
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Also possible it's simply an indicator problem. Only way to be sure would be to get a pressure gauge on it or you could gamble on replacing the oil pressure sender.

Curious it started right at the oil change. I suppose they could conceivably have filled it with a lighter weight oil than your car calls for. In that case you might try a botttle of STP or other oil treatment; it will increase the viscosity some.

Silly question, but you've pulled the dipstick and made sure the level was up to the mark?
 
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Old 11-05-09, 05:37 AM
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If I had a Dodge that was that old, I would take it to a real garage and not just a Jiffy Lube and have it checked by a Trained Mechanic.

It could be that the crankcase is not full of oil. Did you pull the dipstick and read it with the car on the flat and level to confirm that the engine is full of oil - to the mark on the dip stick.

Oil pressure is dependent on two things. A certain amount of viscosity - thickness of the oil, which modern engines only calls for 5 w 30 oil in most cases, and a certain clearance between the moving parts inside of the engine and the bearings.

If you had a bad bearing, or a spun bearing, your oil pressure would change, as would it if you had a worn oil pump.

More and more people, who normally would only change their oil once a year if ever, is going to these Jiffy Lube places and pampering their vehicle to regular interval oil changes due to the fact that they can no longer afford to buy a used vehicle every couple of years and are trying to hold on to and prolong the life of the vehicle they presently own.

I have seen used cars that did not have their oil changed for thousands of miles and when we pulled the plug, the oil came out like Molasses.

If someone put off changing the oil for a prolonged period of time and then decided to change the oil, might find out that the parts inside of the engine have worn and and now you have no more oil pressure.

I am a firm believer in changing my oil every 3,000 miles, regardless of what type of oil you are using. Oil does not wear out, it merely gets dirty. The dirt circulating through the oil acts like a scouring pad and wears out the bearings and moving parts. The carbon blow by from the combustion of fuel is what causes the oil to get black.
 

Last edited by the_tow_guy; 11-05-09 at 02:19 PM. Reason: No need to bash anyone.
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Old 11-05-09, 09:26 AM
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Thanks for the quick responses. And I should have mentioned that the oil is filled to the correct level, and I asked them to put in the same brand and weight of oil (Castrol 5W30) that I've put in the car with every 5000km oil change since I bought it brand new. In fact, I'm very religious on the frequency of my oil changes; I rarely go more than 100km past the 5000km target before it gets changed.

I suppose it's POSSIBLE they put in the wrong weight of oil, but would putting in a 20W50 or something really make the oil pressure light come on after 7 or 8 minutes?

The sensor problem sounds like not an awful thing, but to me it doesn't seem to take into account the fact that I need to rev the engine even HIGHER as the engine temperature increases (to avoid the light coming on). The sensor seems to not read any pressure problems when the oil is colder.

BTW, this has all been happening with quite pleasant weather (20c/70f daytime and 10c/50f low overnight).
 
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Old 11-05-09, 01:41 PM
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20W 50 is a very heavy oil and would cause the oil pressure to go up, not down.

Just think about oil like this.

Take a bottle of maple syrup and pour it down the drain when inside of a house that is 70*. At 70* - the syrup will pour out of the jug as fast as you can pour it and there is little resistance.

Take the same bottle of Maple syrup and put it in the refrigerator until it gets down to 34* or what ever you keep your refrigerator then try to pour it down the drain.

Now it will not pour as fast and is harder to squeeze out of the bottle.

Now put it in the freezer overnight and then try to pour it.

The reason for the numbers is to tell you how this oil will pour when it is warm and how it will pour when it is cold.

Hence when the oil is hot, it will pour like a 5 weight oil.
When the oil is cold, it will pour like a straight 30 weight old.

That is where the 5 w 30 number comes from.

The 5 weight is like the syrup at room temperature and the 20 weight is like the syrup at 45*

90 weight gear oil is kind of like the syrup at 36* inside of your refrigerator.

I would suspect that you have some sort of problem with something on your car and you need to have a mechanic look at it. It could be as simple as a bad sending unit or as bad as worn bearings or a leaking seal or a bad oil pump.
 
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Old 11-05-09, 03:45 PM
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Since you're pinpointing the time this started as at the oil change, I would pick up a filter at a parts store and put it on yourself. With your frequency of oil change the new oil wouldn't drop the pressure if you normally run a 5w low end viscosity.
 
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Old 11-05-09, 08:21 PM
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Originally Posted by Claw Hammer
I would suspect that you have some sort of problem with something on your car and you need to have a mechanic look at it. .
Sorry. I couldn't help myself.

More specifically, my Haynes manual for my Dodge says one cause of low pressure at idle is the idle could be too slow. Maybe not in your case from what you are saying, but something for anyone to remember.

Another cause, besides already suggested catastrophic engine/bearings wear, is if the engine is hotter than normal. That coupled with 5W could put it over the top.

At idle, at traffic lights, the fan needs to come on when it is supposed to. If you have an engine coolant issue.....you losing any?.....even a tiny bit over time? Do you happen to know if coolant level rises in the reservoir when hot, then returns to the lower level when cool, as it should? Or, does it stay the same no matter what (indication of real low level or that it is taking in air from somewheres it should not)?

Or air pocket in the system, that can wreak havoc as to when the stat opens or the fan comes on.

I realize that you did not say that your engine indicates it is extra warm. But because the gauges sense temp best when submersed in coolant, you might confirm what temp your engine actually is, by shining an infrared thermometer at the engine. With mine, I get the highest exterior readings around the spark plugs.

You do not ever notice the engine try to ping or run-on after you shut off the key, do you?
 
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Old 11-06-09, 01:17 PM
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I would rule out the oil pressure sensor
I know the 2.7 liter engines had a problem with them.
There is a factory fix.
I forget what it is. I will post it if I find it.
I would find the problem.
My brother in law lost oil pressure from the oil sensor malfunction and it lost all oil in minutes.
 
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Old 11-06-09, 02:42 PM
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tsb # is 08-36-99

That is the Technical Service Bulletin you could research
I would still get a gauge on it and find oil pressure.
Could be coincidence that it started after the oil change.
Different properties between new and old oil could have been the straw that broke the camels (sensors) back.
 
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Old 11-09-09, 06:31 AM
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It sounds like your oil pressure sensor is still working predictably in conjunction with your oil temp sensor.
When your engine is cold your pressure sensor looks for a certain pressure that isn't as specific as the pressure it expects to see when your engine reaches operating temperature. It then looks for the pressure it's programed to expect based on the 2nd weight rating of oil your engine requires.

Caution - Opinion coming up: The fact that you can consistantly shut that warning off at by boosting it with relatively low RPMs indicates such a narrow threshold between right and wrong that it could very well be attributed to the wrong operating weight. But, of course, you don't want to be at any such threshold! So If this was my car, I'd just make sure that I had the right grade of oil in it as step one. Heck, I might even redo everything the oil shop did and put on a another filter as well. Maybe the anti drainback on the filter gets screwy at operating temp?
 
 

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