I am fed up with the electric OP gauge (factory job) giving me variable readings, anywhere between zero and 50psi when the engine is running.

So, I have at hand a gauge that I can fit which uses the oil pipe similar to one fitted to my Mini Cooper. Originality will have to take a back seat.

My question is, does the air have to be bled out of the pipe until oil flows from the end that fits up to the gauge i.e. will any air in the pipe give an inaccurate reading?

Thanks for any advice.

 

You don't have to bleed the pipe, some pipes are not detachable from the gauge, so could not be bled.

The air will compress under pressure from the oil, the only thing that the air will do is to slow the response time of the gauge. The air compresses more than the oil, so the oil will have to move up the pipe further to compress the air. But at 50psi this won't make much difference.

The gauge will not show any difference, pressure is pressure no matter what medium you measure, it's just the amount that any material will compress under that pressure.

Unlike a brake system, the displacement is not an issue, on a brake system the master cylinder will only move a certain volume, this is a much higher pressure, and the air compresses more so there may not be enough displacement volume to compress the air and reach the pressure required.

The spongy brake pedal is the brake fluid compressing the air, if you pump the brakes, you shift more volume and you can compress any air further so the brake becomes harder.

 

I have a mechanical gauge from a Mini _ best thing I could have done.

 

If the gauge is working properly, which you can test with a variable power supply, the worst issues are with the sender units, they are mechanical internally and can be susceptible to vibration causing problems.

I will most likely fit a solid state sender instead of the mechanical/electrical sender and keep the original gauge, together with fitting a solid state voltage stabilizer.

Providing my gauge is working properly then this should provide a good solution whilst maintaining the original gauge.

This is just my thought process of course.

 

The original Jaguar chrome bezel fits on the mini one.
The numbers have smaller increments, but that's to be expected on a more accurate bourbon tube gauge.
Other then the numbers being smaller, it looks good.
You would get points knocked off of course in concours if you're into that.

 

Thanks for all the replies. Yes, the brake fluid situation (air in lines) sort of had me worried.
Similar perhaps to injecting air into human veins - not a good idea either!