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Oil Pressure Light/Switch


cetheri

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After short periods of driving at highway speeds (2200 RPM and higher), and then slowing to a stop (idle RPM), I noticed that my oil pressure light will flicker on and off, but will go off and stay off immediately when I get going again (add some RPM's). When the light comes on, I detect a very slight change in engine RPM (the tach needle will bounce downward just slightly) and then return to normal again once the light goes out. The car now has 97,000 miles on it. Could this be a faulty oil pressure switch that has aged to the point where it is no longer accurate, or is it more likely an oil pump issue? Also, looking at the oil pressure switch on my car, it does not look like it can be removed with a wrench. The fastener looks knurled rather than the conventional hexogonal shape. Suggestions?

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I forgot to mention that this does not happen very often on short trips where the RPM's are generally below 2200 RPM.

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  • 4 weeks later...
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I am glad I saw this post today. I have a 1989 Coupe Deville with a 4.5L engine and the exact same thing is happening. Almost every time after being on the freeway for a while, the engine oil light will start flickering. I am going to try and replace the engine oil temp. sensor and see if that fixes it.

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I am going to try and replace the engine oil temp. sensor and see if that fixes it.

You mean the "oil pressure switch", right?

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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  • 1 year later...

I went under my 98 Deville to replace the oil pressure switch. It appears to be tight against the front engine mount such that I can't get the clip on the electric plug to open enough to push the plug off the switch. Does this sound normal?

I just put a new left head gasket on this car (thanks for all your help on that!) with the engine in the car. We took this engine mount out and the exhaust piping. The electric plug clip is facing downward (we didn't move it at all) and seems to be in contact with that mount.

Ideas?

Thanks.

Claude

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Forget the last post. I managed to get the plug off by removing the oil filter and then turning the sensor a little bit.

The new sensor is installed and now the "low oil pressure -- stop engine" message is constant.

I am wondering if the sensor being tight against the engine mount, then in my fiddling to get it replaced, one of the wires broke? If the switch is open when there is no pressure, wouldn't a broken wire do the same thing?

Next question -- If the sensor and wires are OK, what would cause low pressure?

The oil pump looks like there is nothing to break or wear out. We had the pump out of the car when we pulled the left (front) head. Torqued the damper to specs.

Oil level is fine -- I keep checking that.

This is 4.6L engine in 98 Deville.

Any suggestions will be appreciated.

Claude

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OK, so forget the last two posts. After more thorough reading of Guru's information on this and the Cadillac Forums, I boiled it down to 3 possibilities:

1. Stuck check valve

2. Problem with the intake screen

3. Harmonic balancer bolt too loose.

#3 Seemed like it might be more consistent with the fact that the car ran 1500 miles before the problem surfaced. Then it surfaced gradually -- the indicator light would go off if I revved the engine. By the third day there didn't seem to be any pressure at all.

I put the wrench on the balancer bolt and it came loose almost immediately with very little effort.

Now my question is: What is the torque and angle to properly install this bolt?

Thanks

Claude

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