Accuracy of a gas gauge in a 35 ford

[vetpenny]

The level in my red fluid gas gauge seems to vary when I am driving. I wonder how accurate are these gauges. What are your thoughts?

[Jeff/Illinois]

Not sure about a '35, but the 'newer' gas gauge in our '36 PU is actually very accurate! All my original gauges in the pickup are.

Well the speedo is off a bit, reads slow, but only because we are running 650-16's not the 600-16's A cop actually pulled me over a while back for speeding. It felt great!!

[vetpenny]

The 35 ford has a hydrostatic gas gauge and is not the same as the 36 gas gauge. When I add gas the red fluid rises to a level and remains constant. How-ever after driving the car a few miles, the level increases giving a false reading. Since the gas gauge was just installed does it require that I drive the car several times before it stabilizes? What are your thoughts?

[JimG]

I have been working on trying to improve the function of my hydrostatic gas gauge in my 34 for a last year or so. There is a lot of trial and error involved. The whole system from the tank to the copper line to the gauge needs to have no leaks. There is a copper or brass rod in the gauge that adjusts the fluid level in the gauge. My gauge always read about 1/2 to 5/8" full when the tank was filed. I have been playing with adjusting this rod by trying to add a second 24 gauge brass wire, which did seem to bring the level up to the F mark when full. Over the winter I lost some fluid somewhere and just added some more. My gauge does go down if the car is not driven, but then goes back up when you start driving. The gas sloshing around in the tank and when you go over bumps makes it go up. I am still experimenting. Deuce Lover on this form knows a lot about these gauges and I have been getting advice from him. Another issue is that the red color in the liquid available today seems to fade over time, so you have to redo the liquid over time. The gauge is basically a liquid filled manometer, so if all the components are good, there is no reason why it should not work accurately. My experience says it is a system that takes some degree of effort over time to get it working reasonably well.

[ndnchf]

A very timely discussion. Today I made a deal to buy a very nice '35 Fordor. Unfortunately, the gas gauge is not working. It has a new gas tank, but the gauge shows nothing. I look forward to learning about it.
Steve

[JimG]

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Enclosed are some service bulletins and other information on the hydrostatic fuel gauge that might be useful for you.

[Floyd]

When clean ,installed correctly and calibrated with the proper fluid and original calibration wire, they are totally accurate. They have to be. They are a manometer, no moving parts and depends only on gravity. In theory, they cannot be wrong if they were installed properly.

[vetpenny]

Thank you JimG and Floyd for the service bulletins and comments. Hopefully A&L in Canton, Conn will have the parts and red fluid if I need them.

[ndnchf]

Thanks for the service bulletins and info. My learning curve is steep here.

[Terry,OH]

Renners Corner sells red gauge fluid that they have used in their gauges for 6 years without any change in color. They also sell some repair parts. Look on their web site.

[ndnchf]

So studying the sending unit, there are no moving parts - right? So long as the holes are clear and there are no breaks, it should be good. My car has a new tank and the sending unit is installed. I've not yet traced the air line to confirm it is hooked up. I hurt my hand last week and am somewhat limited at the moment. Does the wire in the gauge unit simply adjust the level by displacing a little fluid? How hard is it to remove the gauge and check it out and fill it?

Thanks,
Steve

[deuce lover]

Its easier to remove the speedometer first to gain easy access the gas gauge. In looking at the rear of the gas gauge you will see a nut that secures the air line(to tank) on the brass hex.Carefully unscrew it and take off the line with it.There is a ferrule soldered to the air line. There are 2 screws that secure the gauge to the gauge housing.Remove the gauge and service it. Here are pics of the brushes I use to clean the sight glass and hex tube using acetone or lac thinner-the cleaner must pass thru from the hex to sight glass easily.They(brushes) are on Ebay for $6,after blowing out the cleaning fluid ,Refill it (using a syringe-I found on Amazon ,$3)with the fluid to the empty line.Reinstall the unit and air line.I use a light smear of non hardening sealer on cone of the ferrule to be sure of no air leaks when nut is tightened down just snugly . Fluid is currently available at Renner's Corner in MI.Here are pics of what your gauge looks like out of the housing.

[ndnchf]

Originally Posted by deuce lover

Its easier to remove the speedometer first to gain easy access the gas gauge. In looking at the rear of the gas gauge you will see a nut that secures the air line(to tank) on the brass hex.Carefully unscrew it and take off the line with it.There is a ferrule soldered to the air line. There are 2 screws that secure the gauge to the gauge housing.Remove the gauge and service it. Here are pics of the brushes I use to clean the sight glass and hex tube using acetone or lac thinner-the cleaner must pass thru from the hex to sight glass easily.They(brushes) are on Ebay for $6,after blowing out the cleaning fluid ,Refill it (using a syringe-I found on Amazon ,$3)with the fluid to the empty line.Reinstall the unit and air line.I use a light smear of non hardening sealer on cone of the ferrule to be sure of no air leaks when nut is tightened down just snugly . Fluid is currently available at Renner's Corner in MI.Here are pics of what your gauge looks like out of the housing.

Thank you, this is very helpful. I need to trace the air line from the tank and make sure it is in good shape. I'll order some fluid from Renners. I think I have a set of those little brushes. Maybe there is hope of getting it working 😀

[Terry,OH]

mdmchf: There appears to be something over the end of one of your copper lines coming from the sending unit, that does not appear to be as original. The crimped off end of the second line with the small vent hole on the top of the line is correct

[ndnchf]

Originally Posted by Terry,OH

mdmchf: There appears to be something over the end of one of your copper lines coming from the sending unit, that does not appear to be as original. The crimped off end of the second line with the small vent hole on the top of the line is correct

Yes, it has a rubber cover on the end. Is this another vent in addition to the one next to it with the small hole? It looks easy enough to remove.

[deuce lover]

Yes,they are both vents