Have had my '65 A100 for six years and the oil pressure gauge has always read 0. The 225 ran well so I wasn't worried (and there was plenty of things to fix). When I checked behind the gauge there was no line to the engine. The slant was from '76 and I just put a '65 engine into the truck which has a port tapped in passenger side. I have the appropriate oil line installed now and am about ready to fire up. Do I have to bleed the line for it to work properly? Thanks

Gary

I can't imagine why you'd need to bleed the line. I certainly never have. (I'm assuming you're talking about a mechanical gauge, that has a tube going all the way from source to destination.) Unlike other hydraulic control systems where air pockets are problematic, this is merely measuring pressure. Any air pockets will be squeezed by whatever pressure is presented, in which case they'll change in size slightly but I'll bet that effect is too small to notice... Long story short, regardless of the compressibility of any portion of the contents, there's nothing that would prevent pressure inside the tube from telegraphing all the way to the gauge.

- Erik

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.

Thanks Fanatic. First time in the category for me, and I was unsure how it worked. G

I have always bled my Mechanical Oil Pressure gauges Lines.

I thought if I bleed the brakes, and the coolant system then why not this too.

It's easy to do. I have never tested to see what if any error comes from having a `3foot line filled with air vs. one that was bled.

Greg

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http://www.youtube.com/hyperpack

The brakes matter because a bubble of compressible substance reduces total fluid movement.
The coolant matters because a bubble gets in the way of heat transfer.

There's nothing wrong with bleeding air bubbles in a pressure tester if you want to... but in this unique case, the volume (or volume change) inside the tube is irrelevant. As long as whatever substance in the tube is free to move (e.g. not blocking the tube), you can put ~50psi into one end of a tube and you get the same pressure out the other end, you've achieved your goal.

The original poster's question is understandable. I cannot think of any other system where having a mixture of stuff (compressible vs non-compressible) offers no detriment.

- Erik

_________________
Lots of early Valiants and Barracudas have crossed my path.

Also a handful of other toys for variety now and then.

I think the air in the line eventually disappears............

Not by leaking, but by being absorbed into the oil slowly.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes