The Stovebolt Site Forums The Shop Area Engine Shop Oil pressure gauge dumb question

I've got a '46 1/2 ton with a '54 Powerglide engine in it. I've been using the old OEM 30lb oil pressure gauge for more than 30 years. It worked fine, coming up to peg as the truck got OP up. If I drove the truck on a hot day at speed, it might drop down to about 25lbs when I came to a stop, so it was working fine. Now it always reads about 25 lbs with truck turned off. When I start the truck it pegs up to 30, so it works, but it won't return to zero anymore. I think I banged it when I had the dash out to repair my sticky temp and ammeter gauges.

My question is this: How does the pressure tube work off the engine to make the gauge read pressure? Is it a tube? It's not kinked anywhere, so I think the problem is in the gauge itself. I can see how it's attached at the block, obviously, but how is it attached at the back of the gauge? I'm afraid to pull on it too hard, since I don't want to mess th gauge up anymore than I (apparently) already have. Frankly, I'm trying to avoid pulling the dash again unless it's a last resort - just can't get at the screws to take the plate out that holds ammeter and OP gauge.

Any suggestions welcome. ...and I proudly accept the nomination for dumb question of the day.

A Bourdon tube pressure gauge is a flattened piece of tubing that makes about a 270 degree arc inside the gauge housing. As pressure is applied the tube tries to straighten out. That motion is transmitted to a geared spindle that the needle is attached to, which turns and makes the needle move. It sounds like the gear has slipped a few teeth. Try taking the gauge out of the dash and see if you can reposition the spindle gear to make the needle read zero again, or close to it. You can use air pressure and an adjustable regulator to test the gauge for accuracy. Yes, the line from the engine to the gauge is a hollow tube, about 1/8" outside diameter.
Jerry

Here's a good tutorial video:



Jerry

Also you could swap it out for a GMC ga from '39-'46 and have your full 60 psi. Good luck

Thanks very much. Was going to tear into this past weekend, but got sidetracked by other things. Might be a good thing - I feel like I've got a better understanding now. Much appreciated.

All fixed. Thanks for the suggestions. The Youtube video was a great explanation, so when I got it apart I knew exactly what I was looking at. Thanks, Jerry. Put the repair details in another thread dealing with this problem.