2001 V70XC - Noticeable loud pop before ignition

[xHeart]

There were similar but random, infrequent, one loud pop nanoseconds before ignition last winter.

Two suggestions were made to remedy the issue: 1) possible frost at the condenser drain; 2) low oil pressure.

It is fall weather, but it will root out the condenser drain - where is it located for access.

Is it then oil pressure sensor, oil pump? ...thoughts?

[regent]

If you suspect that low oil pressure may be affecting the VVT, have you checked for related codes (may find some pending that will not always set the MIL).

To rule out oil pressure and sensor, I would just use a direct reading pressure gauge in the sensor port.
Not exactly sure I understand how the frosted drain may cause the pops right before ignition...

[xHeart]

If you suspect that low oil pressure may be affecting the VVT, have you checked for related codes (may find some pending that will not always set the MIL).

To rule out oil pressure and sensor, I would just use a direct reading pressure gauge in the sensor port.
...

No code at this time.
The oil lamp stays on at POS II, but then goes away at ignition. Is this normal?

Picking up a loaner gauge from local O'Reilly.

[regent]

...The oil lamp stays on at POS II, but then goes away at ignition...

Let's clarify ignition key positions:

Pos. II = Ignition ON (all trouble lights in general come on for an operational self-test; the oil lamp should remain steady ON)

Pos. III = Starter ON.

The oil lamp should go off as soon as the pressure switch detects sufficient pressure, normally upon successful engine start

[xHeart]

...The oil lamp stays on at POS II, but then goes away at ignition...

Let's clarify ignition key positions:

Pos. II = Ignition ON (all trouble lights in general come on for an operational self-test; the oil lamp should remain steady ON)

Pos. III = Starter ON.

The oil lamp should go off as soon as the pressure switch detects sufficient pressure, normally upon successful engine start

Helpful.
Oil lamp is working as normal.
Does it mean oil pressure sensor is reading the oil pressure correctly too?
Would the direct gauge test verify or otherwise?

[regent]

With a gauge, you can read the actual oil pressure at different engine RPM and compare it with the specified values for your engine; a good Oil P-sensor and trouble light can only alert you that the pressure is below minimum.

[xHeart]

With a gauge, you can read the actual oil pressure at different engine RPM and compare it with the specified values for your engine; a good Oil P-sensor and trouble light can only alert you that the pressure is below minimum.

Thank you regent.

The loud pop is random.
The oil level appears safe between the dipstick markers.
Should it be assumed that Oil P-sensor malfunctioned, and the oil pressure is indeed low?

Why would the oil pressure drop -- is oil pump failing?

[oragex]

I had this when I bought mine. It did a 'clunk' right when after cranking the engine would fire up. I remember I was worried about rod bearings or a sticking oil ring. After I switched to synthetic and a better filter, I haven't heard it any long . I also poured some top engine cleaner inside the cylinders and let them overnight, but I don't remember exactly if this was afterthe noise had solved or before. What I remember is that it took my O2 sensor but it was old anyway.

[xHeart]

The oil and filter change occurs every 4 months since several daily trips are 3-6 miles.

Now running on fresh Mann and Pennzoil 5W30. I will have time next weekend for a gauge to check for oil pressure.

Asking myself, if the pop was due to cold weather, then it should not happen while parked in heated garage overnight -- !!??

[xHeart]

I ask Volvo service if anyone there may know about the metal-to-metal pop before engine starts. They say it is hard to diagnose since it is a random event, but recommends looking closely for clues around engine and transmission mounts. It could be as simple as using new bolts. That is what they would do first.