oil pressure...

[Alfisti2b]

I know this topic has been discussed at length, but a search of the forum didn't give me the answer I was looking for.

Even though I am considering selling my Alfa, I have been driving it quite a bit lately and enjoying every second of it. Today, after about 45 minutes of mostly highway driving followed by some stop and start, I noticed that my oil pressure gauge had dropped to zero at idle. In the past it was always right at about 25 psi at hot idle. The temperature gauge never exceeded its normal range of just north of 175F at which time the fan engages. When I lightly revved the engine the gauge did perk up to about 20 psi, but not to its normal range. Luckily I was close to home and turned the car off immediately. The oil pressure light never went on. No irregular noises. The dipstick showed no loss of oil. I know sender failure is common, but I wanted to verify a couple of things. With the engine off and the key turned to the accessory position, the oil pressure still shows zero even though the engine has cooled considerably and the red oil pressure light is on. Out of caution, I didn't restart the car. When the key is turned to the accessory position with the engine off, does the oil pressure gauge usually give a reading? Does the oil light normally come on? I can't remember.

I am happy to replace a bad sender, but don't want to take any chances with spun bearings etc.

Thanks for your help.

[Alfisto Steve]

There is no accessory position on the key it is off - on - start. Do you mean on?

In on position but engine not running red light should be on and needle 0. Once started in on position red light should go out but needle may not move much if hot or sender going bad.

If oil level up as you indicate it is probably a bad sender. I usualy get 55 psi cold and after running awhile about halfway and then hot may drop to zero at idle and only go up partway when driving but goes lower as engine gets hotter.

[Michael Smith]

The oil pressure gauge sender is notoriously poor quality. The unit does not hold a reading. With the engine off the oil pressure drops to zero.

If the sender goes bad it reads low when the engine is warm. At idle the displayed pressure approaches zero but revving the engine will show some pressure.

If the oil pressure warning light goes on when the ignition is switched on and turns off when the engine starts then the oil pressure is fine.

Oil pressure gauges are a waste of time with modern multi grades. Not much oil pressure is required to provide adequate protection. What is useful is an oil temperature gauge to allow you to see when the oil is warm so that you can drive the engine hard.

Looked at as an oil temperature gauge (the pressure drops as the engine oil warms up due to viscosity effects) the oil pressure gauge in the 164 is still useful even when not working correctly. It can be used as an oil temperature guide. The gauge needle drops as the engine oil gets warmer!

[Alfisti2b]

Thanks guys, that's very good news. I was worried that the loss of oil pressure (or at least the gauge indicating loss of oil pressure) may be indicative of major problems. As I mentioned, I am looking to sell the car and obviously would not do so if I thought the car was on the verge of major mechanical issues.