Okay so I need a gauge and 1/8" threaded pipe. Thanks.

 

there's no inches on a volvo, the oil pressure sensor is going to be metric like everything else. only thing I can suggest is pulling it out and measuring it, also the thread pitch.

the B230 engines (1985+, I think?) use one like this, while the older b18-b23 engines used a smaller one.

 

OK sorry as I made some assumptions here. As Pierce mentioned you need to find the thread size of the low oil pressure sensor. Once you have that you need an adapter to fit into that hole. The adapter should have a 1/8" compression fitting for 1/8" plastic or copper tubing. You need to get/buy an oil pressure gauge from an auto parts store. Run the tubing to the rear of the OP gauge and tighten the fittings. Start up the car and see what the pressure gauge reads. With the engine cold and running at around 1000 rpm gauge should read between 20-40psi. As the engine warms up it should read about 15-20 psi at idle (700rpm). At 2000 rpm you should be running around 40 psi. Let us know what you do.

 

Thanks.

For reference, the parts!
Multipurpose Gauge, Plastic Case, 2" Dial, 1/4 NPT Bottom, 0-100 PSI
Multipurpose Copper Tubing, 1/8" Tube Size, 1/4" OD, .152" ID, .049" Wall, 10' Coil
Brass Yor-Lok Tube Fitting, Straight Adapter for 1/4" Tube OD x 1/4 NPT Female
Brass Yor-Lok Tube Fitting, Straight Adapter for 1/4" Tube OD x 1/4 NPT Male
1/4 NPT Female Adapter x M14 x 1.5 Metric Male

I just started it today and it sounded fine, but I didn't let it warm up. The other day I started it warm and it made the noise. I'm going to change the oil/filter and add some Lucas oil treatment to see if that helps quiet it down.

 

Went to change the oil and both front motor mounts are sheared. yay.