Morris Minor Owners Club

May seem to be elementary to those with more experience than me but when connecting up the capillary pipe to a smiths oil pressure gauge do you need to 'prime' the pipe with oil and then connect up to the guage to ensure carefully that no air bubbles are in it for a more accurate reading? (it seems a very tiny bore pipe anyway)
Thanks in anticipation for any feedback as always

How are you going to prime it? You will have to turn the engine over to pump the oil up the pipe and it will then squirt out of the top end - messy. As soon as you stop pumping the oil will flow back down the pipe before you have connected it to the gauge. Just connect the pipe and ignore the air, it will not make any difference to the reading.

Thanks - It was an "expert" that certainly confused me in saying you leave the union slightly loose on the back of the guage until oil just oozes after starting the engine then tighten ??
Yes - will just connect it up as you explained - ! .

I would have 'wondered' the same as you, the 'expert you mention is not necessarily wrong, his method is a recognized way of priming so to speak, and I'd have done the same but do as Mike says first, I'm sure you'll be ok, you can always loosen the union if there is a doubt.

If you get a very jerky reading from the gauge, loosen the gauge end tube nut very slightly while the engine is running to remove the air - makes the gauge respond instantly, if it didn't already before.

Does the response of an oil pressure gauge really matter? I - suspect it will actually respond faster with air in the pipe - after all - air flows much more easily than cold sticky oil! Just connect the pipe and enjoy the readings.

air compresses easily compared to oil,and will expand again when the pressure is off,after the initial squash , I'm not sure if it will make a great deal of difference

my brain is hurting

It's an oil gauge not an air gauge, why not crack the union nut see a bit of oil, tighten and have done with it!!