- Home
- About Us
- Join/Renew
- Member Benefits
- Member Pages
- Log In
- Help
- Museum Store
Gents,
I have a spare Oil Pressure Gauge for my Series 80 and the needle does not sit on the resting peg (at – 0 pounds).
Instead, it hovers at +/- 20 pounds.
I fooled with it a bit to no avail, and I do not wish to break it.
Does any one have a suggestion on how to properly calibrate the gauge?
Peter
Was that a Borden Tube type gauge? Maybe you could pull a vacuum on it and recurve the tube. Jim
Jim,
I just did an internet search for a Borden Tube type gauge.
The answer is, YES!
So what I think is a circular spring is actually a tube, correct?
If i put a hand operated vacuum pump on it, should it move and adjust the pointer?
I guess that i will see.
I hope that I didn’t already mess it up.
I’ll study the internet info.
Thanks,
Peter
Peter,
I believe it’s an oval brass tube in a circular shape. It might need a vac pump that can draw down to 28″ and hold it. Jim”
If the back of the gauge is exposed, there is a ‘U’ shaped part of the gear ‘rack’ that moves the ‘pinion’ on the shaft of the needle. Using a pair of needle nose pliers to pinch the ‘U’ narrower, or using a small screwdriver to wedge into he ‘U’ to widen it will move the gear rack and move the needle to the zero position.
I’ve done this quite a few times. it’s tedious work, but doable.
Greg Long
Gents,
I got the needle to rest at ZERO after a bit of fooling around.
Thank you.
Does this unit work on vacuum pressure, or positive pressure?
I suspect the latter.
The original oil pressure gauge installed in my Series 80 pretty much stays at 20-psi on startup and I believe that is should be substantially higher until the engine oil warms.
Would it be useful to first check the lines to see if they are plugged and then consider fooling with the oil pressure adjustment on the driver’s side of the engine?
I could swap out the gauge sets after I check the oil lines and then I could see if that spare gauge shows different numbers.
What do you think?
Peter
Gents,
BTW, it is a BOURDON type gauge.
Eugene Bourdon (1808 – 1884) was a brilliant French watchmaker and engineer who invented the Bourdon gauge in 1849.
Peter
Your S.80 engine should peg [>100psi] the gauge when it is first started, as the oil warms it will drop to normal pressures.
Normal HOT oil S80 pressures: 0-10 psi at dead-slow idle, 20-40 psi at 40mph.
The pressure regulator is primitive and not able to handle the high pressures with cold, thick oil.
Change to a known good oil pressure gauge, or just any other gauge and compare readings.
I would recommend removing the oil line from the ‘T’ on the engine side of the firewall, and at that location try different gauges. This location is much easier to access than under the dash inside the car. And any oil spills or leaks are wiped up, instead of staining upholstery.
I would also suggest testing the gauges from an air hose with a given pressure, something like 40-50 psi is safe and easy to use.
Greg Long
Peter,
It was 50 years ago when I heard of Bourdon tube gauges, I’m lucky to remember Borden let alone how to spell it. I wasn’t paying that much attention then since I knew it all, now I realize how much I don’t know. I just thought a vacuum might be able to nudge the tube back into shape and not have to deal with the adjusting. Jim
Greg,
Thanks for your input.
I did review the Series 80 Owner’s Manual and noted the operating oil pressures, both Hot & Cold.
I had some recollection that one of the Series 80 Boys told me that their Series 80 ran 50 to 80-psi when cold, but that it dropped as the engine got to normal operating temperature.
I was going on that recollection.
Currently, at an ambient temperature of about 75-degrees F, the engine pumps out 15 to 20-psi at start up.
I have yet to have the opportunity to drive it a bit to get the engine to operating temperature.
The good news in all of this is that the gauge about which I was writing is a SPARE unit!
Again, thanks for your input.
Peter
Jim,
HA!
A memory is a terrible thing to lose, and mine is floating around here somewhere.
Your recollection caused me to find the Bourden type gauge and to understand its operation.
Applying a vacuum does indeed pull back the needle.
It’s just too bad that I did not do that FIRST, as it might have saved me a bit of fussing with the mechanics.
After fussing, I tried your solution an it works well.
Thank you.
Peter
With the initial start-up oil pressures capable of being in excess of 100psi, overpressure of the Bourdon tube tends to try to straighten it out. Our Pierce gauges are made to register up to 100psi. But revving up a cold engine can damage the gauge.
Pulling a vacuum on the gauge WILL pull the Gauge back, BUT, pulling a perfect vacuum will be only a -14.7psi at sea level. Pulling a perfect vacuum is difficult, probably using an air conditioning vacuum pump would be the most effective.
I’ve not used a vacuum to attempt to re-calibrate a pressure gauge, but it seems unlikely that a negative 14psi would correct the mechanical distortion in the Bourdon Tube when it’s designed to operate at up to 100psi? I’ll have to look at one when I’m home later this week.
I’ve used an air pressure source, like an air compressor with an adjustable pressure regulator to create a 40-60 psi pressure source to check oil pressure gauge readings. Being exact is not critical. Just knowing your gauge is indicating within say +/- 5 or 10 psi will be accurate enough. The oil pressure developed in our engines varies with rpm, temperature. and the internal engine temperatures created by engine load.
You can have an engine with a good cooling system not show a rise in temperature when the car is climbing a grade, but the internal temperatures will rise considerably. The engine oil is an important part of cooling the internal parts of an engine. So oil temperature can climb considerably resulting in low viscosity and lower pressure. Just knowing that the pressure is lower than normal is enough information.
Greg Long