Instrument Pod

Oil Pressure Gauge Always Pegged High

Something is wrong with my oil pressure gauge. When the car is turned off the needle sits at the bottom off the scale (below 1 bar). When the ignition is turned on (engine still off) the needle jumps to a point over 5 bar. Start the engine and the needle stays over 5 bar and remains at this spot when driving with no discernable movement from idle thru to WOT. Is this normal? I don't believe so as I have read posts talking about the pressure being around 2.5 bar at idle and moving up to 5 bar at WOT. What should my normal oil pressure be? I am currently using Castrol 20 W 50.

Just spoke with my mechanic, his first thought is that it is the oil pressure switch (cost cdn$100/US$65, plus 1/2 hour labour for re & re) but might be sticky gauge ( few 100 $, plus couple hours labour). My mechanic has a good reputation so I do not feel that he is leading me astray. however I have only had the car for a month and a half and would like to be armed with as much knowledge as possible when I bring the car in to the shop next Wednesday. Do these sound like fair assessment of the problem? Because the needle does move, I am inclined to believe that the switch is the likely problem. Is there anything else that it may be that I should be aware of?

TIA
Rob Sneek
'87 928 S4 5spd. Marineblau Metallic



Robert,

Does the pressure drop after the engine warms up? It is normal for the oil pressure to be pegged at idle when the engine is cold. As the oil thins during warm up, the idle pressure will drop to the 1.5 - 3 bar range.

Before changing sensors and gauges, check the electrical connections both at the sensor and to the instrument pannel. Bad connections at either end will yield bad readings. There are two connectors to the instrument pannel that should be checked. The 928 uses a flexible printed circuit board between the connectors and guages. Use an eraser and electrical contact cleaner (not the tuner cleaner /lubricant) to clean the PCB connector "fingers." There are also cases where the PCB goes bad and the gauges are good, so if you yank the pod to replace the gauge also consider changing the PCB.

Rich
'93 GTS
'83S



First off thanks for the help. I will check the contacts this weekend before I take the car to the shop next week. Any thing special I need to be aware of when taking off the instrument pod?

Regarding the pressure dropping after warm up, no it does not drop after the car has reached operating temp. Needle stays pegged over 5 bar.

Thanks again,
Rob Sneek
'87 928 S4 5spd. Marineblau Metallic


No need to remove the instrument pod, the connectors can be removed and cleaned without removal.

BTW PCB means Printed Circuit Board.

Rich


Like Bill Cosby said, "you need to burn the gunk out". Mine did the same thing for a few months. You need to remove the pod, and clean up the unit. My wrench told me that because of the angle of the circuit back there, it's prone to collecting schumtz. Cleaned my up and now works perfectly. Hope this helps.

-PJ



I had a similar situation after doing some engine work on my 84. The oil pressure gauge was pegged high at all times after starting the engine, this after putting in a NEW sender. I was rebuilding the engine and had it out of the car, so I had installed a new sender. It turns out the electrical design of the sensor circuit is such that reversing the two connections at the sender will cause the stated problem. Swapping the connections of the two wires at the sensor corrected my problem. There are doubtless other possible causes, but mine was simple.

Jeff Herhold
84S