High Oil Pressure (indication)

[fjmuurling]

Almost all oil pressure problems are low oil pressure (indication).

I have the opposite namely a high oil pressure (indication), when the engine is idling the needle  of the dash gauge goes completely to the rightside past the 7 mark.

I have done the following in order to try to solve the problem:

• Replaced the oil pressure sender however it didn't solve the problem
• Measured the oil pressure with a gauge. (T junction made at the oilfeed line coupling at the turbo). Measured 4.5 bar engine idling 1200 RPM, measured 5.0 bar at 3000 RPM (engine / oil was cold), indication in the dash was 7+
• Checked dash gauge indication. removed the "WN" (White - Brown stripe) wire from the sensor and connected a potentiometer to it. See table below. No obvious misreadings / indications. The gauge indications in relation with the resistor values match (almost) the 0 - 184 Ohm curve of a 0 - 10 bar VDO pressure sender. (end point is different).

Gauge Mark	Resistor value (Ohm)
0 - Red	8.23
1st white stripe	48.7
2nd white stripe	70.9
3rd white stripe	86.8
4th white stripe	110.9
5th white stripe	128
6th white stripe - 7	145.5

 

• Measured the resistance between the sender housing and the engine block, almost 0 Ohms (0.1 Ohm), so no problem there
• Disconnected the Oil pressure warning switch wire and started the engine, no joy needle goes to the max.

 

Some other things:

• The Oil in use is Castrol Edge 10W 60, engine filled in may 2019 from unopened/sealed "containers", these have been sitting on the shelf for about 4 years before being used.
• The standard oilcooler flange between the oilfilter and the oilpumphousing is replaced by a thermostatic version (Mocal IIRC).
• I saw the the dash gauge indication drop 1 or 2 times during a testdrive on the highway, everything nice and warm. After a very short time the needle went into the corner again.

 

If anybody got some ideas / info etc for solving the problem I would be more than gratefull.

Freek

 

 

[Erikl]

Wow if the gauge checks out and the pressure from the motor is right - it has to be the sender???  Can you check the out put from the sender at different pressures and see if it matches to your gauge test roughly?

[fjmuurling]

The car was of the road for about 5 years after a headgasket failure.

Since june this year it is running again (okay some very minor problems but all solved except the high oil pressure (indication)).

The above problem manifested itself after the first starts so after eliminating a couple of things I changed the sender for a new one but this did not solve it.

Your suggestion of testing the sender is a good idea. (easer said than done, one of the joys of working on a Lotus), however an old and a new sensor having the same failure/problem seems unlikely but ........................

 

[Escape]

Your findings point to a bad connection somewhere, as a higher resistance will give a higer reading. Did you check the wire from the sender to the gauge? Or the connector to the sender?

Filip

[fjmuurling]

The measurements were taken with the whole cabling. I removed the connectors from the sender and hooked the potentiometer up to the connector and the ground to the engine. With me sitting in the back and adjusting the potentiometer, my girlfriend was sitting in the front reading the gauge and writing down the corresponding resistance value which I measured after setting the needle on each whit / red stripe on the gauge.

So the cabling looks ok. 

[drdoom]

Is there a voltage stabilizer for the power feed to the gauges?

[fjmuurling]

No voltage stabilizer and all other gauges work normal.  

[Escape]

Maybe a bad fit of the connector to the sender? Seems to be the only item left...