1992 Oldsmobile Toronado Fluctuating/High Oil Pressure

Tiny
DJBOCK
  • MEMBER
  • 1992 OLDSMOBILE TORONADO
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 11,600 MILES
1992 Olds Toronado Trofeo, 3.8l with 116,000 miles. Am experiencing fluctuating to high oil pressure. At idle getting a good pressure around 38psi. At highway speed/RPM the oil pressure will fluctuate between the low 60's to mid 90's sometimes even into the hundreds. No reason for the fluctuating as the RPM's are pretty much constant but will be in the 60's for a few miles then up to the 90's for a few miles and everything in between.

Car is only driven in the summer and had the same problem last year where pressure readings were in the 200's. Replaced the oil pressure sending unit when I did my oil change for winter storage and this year it is better but still fluctuating more than I would like.
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Tuesday, May 11th, 2010 AT 8:36 AM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Hi djbock. Welcome to the forum. Run the engine for a bit with the sending unit disconnected and see what the gauge reads. I would hope you find it's still high due to a wire rubbed through making a high resistance short to ground. 200 psi should explode the oil filter, so I would like to think the pressure isn't really that high. As an alternative, what does the gauge read with the engine stopped and the ignition switch on? Naturally it SHOULD be 0 psi.

If the reading goes to 0 psi with the engine off or sending unit disconnected, that would rule out a grounded wire. Normally I'd suggest having the pressure checked with a mechanical gauge, but the likelihood of two sending units being defective is unlikely so they will probably be in agreement with the mechanical gauge.

If everything points to the pressure really being that high, suspect a blocked pressure relief valve in the oil pump, either from debris blocking the port or corrosion causing the valve to stick.

Caradiodoc
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Tuesday, May 11th, 2010 AT 1:15 PM
Tiny
DJBOCK
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Sending unit disconnected the dash gauge reads 0psi, but the MDI digital readout reads 255psi when car is running.

With car off and ignition on both dash gauge and MID digital readout are 0.

So not really sure. I am assuming that the oil pump is located inside of the oil pan? I am fairly mechanically inclined as in brakes, struts/shocks, water pump replacement, exhaust and such, so do you think that I could handle this myself?
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Tuesday, May 11th, 2010 AT 8:03 PM
Tiny
CARADIODOC
  • EXPERT
Suspect a problem with the digital display. There's no way the pressure can go that high. Plus, that much pressure would flood the cylinder walls with oil and overload the piston rings. You would see a lot of blue smoke from the tail pipe. I think your engine is fine.

Caradiodoc
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Tuesday, May 11th, 2010 AT 9:27 PM
Tiny
DJBOCK
  • MEMBER
That could be but during normal driving when it is fluctuating both the dash gauge and digital display are in sync and showing the same high/fluctuating pressures.
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Wednesday, May 12th, 2010 AT 7:57 AM
Tiny
CARADIODOC
  • EXPERT
There's something I'm missing here. How can the digital unit read 255 psi with the sending unit disconnected unless there's a second one? There is most likely a Body Computer involved. If so, the gauge could be getting its reading from the digital unit, but the numbers don't really agree with that either. The place to start is by having the actual pressure measured with a mechanical gauge so we know exactly what the gauge should be reading. You might be able to borrow a gauge from a parts store. A lot of them are borrowing or renting tools now. The hose will screw into the port where you remove the sending unit from.

Caradiodoc
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Wednesday, May 12th, 2010 AT 2:05 PM

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