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I have an oil sending unit problem, getting false reads,oil light on when stopped & in gear, oil is full, how do I change it out or should I?1997 Chrysler T & C minivan, 3.3L. I am mechanically inclined
 

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I have an oil sending unit problem, getting false reads,oil light on when stopped & in gear, oil is full, how do I change it out or should I?1997 Chrysler T & C minivan, 3.3L. I am mechanically inclined
To be perfectly honest, it sounds like your oil sending unit is working correctly.

In my experience, if you are ONLY getting an oil light when the car is warmed up, in gear and idling, you have (most likely) very worn main and/or rod bearings, a clogged intake screen (less likely), or even a failing oil pump (least likely of the three).

Given that you are "mechanically inclined", I'd say drop the pan (very easy to do on these vans), check the screen and plastigauge (http://www.plastigaugeusa.com/how.html) the bearings. Let us know what you find out.
 

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Plastigauge is a good idea, but first check out the actual oil pressure. Get a pressure gauge and attach it in place of the sensor. That will tell you the REAL situation. If you do have low oil pressure at idle, then plastigauge. But note this: If you do a plastigauge test from the bottom with the engine in the vehicle, you have to support the crankshaft with a floor jack at each end. If you don't support the crank, you will get erroneous readings.
 

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I get the false light once every few months. Turning off the engine and restarting akways makes it go away.
 

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It is a problem with the oil pressure switch. The oil pressure at warm idle is normally very low...usually 5-10 psi. This is normal, but over time, the oil pressure switch can "lose calibration" and be off by just .5 or 1 psi. That's often enough to trip the light, because the warm idle pressures are low to begin with.

Best advice is buy a new switch at the dealer. Don't bother with the cheap electrical stuff (Standard or GP Sorsenson) at Advance or AutoZone -- they'll likely have the same problem. The Mopar part from the dealer will be calibrated correctly and your problem will likely go away.

A co-worker had this very same problem on a '99 SWB 3.0 van. I suggested the switch and that was the cure.
 

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False Oil Light With Chime

First Append alert:
I have '98 Caravan 3.0 L with 74k original well maintained miles.
Problem occurs at idle after warmup. Generally after 20 minutes or so of stop & go. First indication is usually on slight upslope. After that always at idle.
Car does not have a Tach or oil pressure guage. Tried several different pressure sending units. Factory unit was worst. Immediately and always at idle. Borge-Warner unit from Autozone was best. Current symptoms as described. Shop tried test drive with gauge but never saw less than 10 PSI.
Every gauge that I looked at for installation had very poor resolution at low PSI. Any increase in engine RPM solves the problem. The two things done that seemed to help the most were changing the idle position sensor. Prob went away for four months. Recently changed oil from 10W/30 to straight
40W and that along with cooler Texas weather has eliminated problem for now. Reviewing the Internet indicates that this is a common problem with several Chrysler products. Does anyone have a simple solution for this? Is there a way to somehow set the idle speed slightly higher. I've thought of putting a tie wrap device on the accelerator cable to prevent it from idling so low.
Incidentally idle is never so low that the engine shows any signs of laboring.
Sorry for the long append but details are important. Anybody have any ideas?
 

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Reviewing the Internet indicates that this is a common problem with several Chrysler products.
Really? Other than the Mitsubishi built engine that you have in your van I've never heard of another Chrysler engine with this problem (unless your talking about a sludged 2.7, but that's another story).

Does anyone have a simple solution for this?
Yeah, new main and rod bearings.

Is there a way to somehow set the idle speed slightly higher. I've thought of putting a tie wrap device on the accelerator cable to prevent it from idling so low.
As most engines these days have an idle speed that is set electronically (not sure about your Mitsubishi engine), I'm thinking that this is a very bad idea.
 

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Current symptoms as described. Shop tried test drive with gauge but never saw less than 10 PSI.
Every gauge that I looked at for installation had very poor resolution at low PSI. Any increase in engine RPM solves the problem.
First off, what is the spec for oil pressure at idle? Your reading of 10 PSI at idle sounds PLENTY high for a modern engine. Many idle with less PSI than that, even when new. I continue to think you don't have a problem with the engine at all, and the problem is in the oil pressure sender circuit.

The answer will come if we can find out the correct oil pressure for a Mitsubishi 3.0L engine at idle. Without knowing that, I don't think there's any way we can make an informed recommendation.
 

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FYI - From a 1997 Chrysler manual for the 3.0 Engine.
Using a gauge at the pressure switch location.
Engine warm (thermostat open).
Oil pressure at idle 6 PSI.
35-75 PSI at 3000 RPM.
 

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Trying a lower pressure switch.

I appreciate the ideas. They got me to doing further research.
The 1998 Chrysler Caravan Service manual says on page 9-90:
For 3.0L engine.
Oil pressure at curb idle speed = 10 psi.
At 3000 rpm = 45 to 75 psi.
On page 9-125 for the 3.3/3.8L engine it says:
Min oil pressure at idle fully warmed up = 5 psi.
At 3000 rpm = 30 to 80 psi. Oil pressure switch actuating pressure min =
2-4 psi.
Checking parts stores, most Caravan 4 cyl and 6 cyl with the exception of the 3.0L use either an SPM PS287 or a Duralast PS278 pressure switch.
The 3.0L uses either an SPM PS302 or a Duralast PS279 pressure switch.
Physically the two switches look interchangable. Thread and connector.

It seems that I can probably use the lower pressure actuating switch from the 3.3L engine. I am going to check this out at the parts store today.

Incidentally I need to add that I have been driving the car for about a year with this sensitive switch problem. There has never been any nasty noises from the engine even after idling for an hour or so with the light on and chiming. Oil pressure at 3000 rpm is a steady 55 to 60 psi.

I could of course just disconnect the sensor, plug the oil port and ignore the problem as I have been told by two different service shops to do.
 

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I could of course just disconnect the sensor, plug the oil port and ignore the problem as I have been told by two different service shops to do.
Are these the same shops that sell and install new/rebuilt engines? Sounds like they are trying to drum up some business. :rolleyes:
 

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With 10 PSI of pressure at idle, you have PLENTY of oil pressure. Exactly what is specified, apparently. I like the idea of using the 3.3L pressure switch. The switches from the parts stores aren't always all that accurate (in terms of their calibration), so false oil pressure warnings can be common. You should have plenty of "wiggle room" if the 3.3L switch is supposed to close at 2-4 PSI...because you have a verified 10 PSI.
 

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Sending units not same thread size

Well, so much for that idea.
The two types of sending units are electrical connecter identical. The problem is that the 1998 3.0L unit is a straight (not tapered) thread close to 1/4" diameter. The 3.3L unit is a straight (not tapered) thread close to 3/8" diameter. A search of hardware and automotive brass did not come up with a suitable reduction 3/8" to 1/4" brass coupler.

Also the 3.0L engine (on another page 9-62) says oil pressure should be 6psi at idle (presumably after warm up).

Theory follows:
The switch is shorted to ground at zero psi with the oil pressure light on.
When the engine speed is greater than about 420 rpm, and that should equate with greater than about 5 psi , the switch opens and the oil pressure light goes out. The switch remains open with the light off while engine is running.

Unless the engine computer polls the oil pressure switch at ignition on, then all one would have to do is disconnect the wire from the switch to fool the system. I guess I will try that next.
 

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How easy/difficult will it be to get the old sensor out of a 10 year old 3.8l engine with 160K miles"? Any tips, tricks?
The oil sensor? Should be a piece of cake.
 
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