With the help and advice of several members and a bypass kit from Walt, I finally got my '51 up and running. It purrs like a kitten. However, the temp gauge goes up almost to the H when driving at highway speeds. I checked the temp using a non-contact temp reader and it shows, when the gauge reads the highest, at 175 at the sender and about 10 degrees cooler nearer the thermostat. there is about a 10 degree difference between the upper and lower radiator hoses. At idle or around town ,the temp gauge rides just about at the 3/4 mark...sometimes lower but when measured with the non-contact temp reader, it shows 162 degrees. My question is...what was the temp that the factory calibrated the gauges to? I had everything flushed before I put in the bypass kit and it has a newer water pump. At 175 degrees, I'm not overly concerned but it's a little unnerving looking at the gauge. I got the gauge cluster from a car I parted and the fuel gauge works just fine. Terry
To help clarify my question, I get the following readings: at the quarter hash-128 degrees ....at the half hash mark-about 135 degrees....a hair under the 3/4 mark is 150. All readings are taken at the sender. I have another sending unit and it reads the same. Does anyone know what their gauge reads at the different hash marks? Terry
By Hudson,1/4 mark is 140, 1/2 mark is 160, 3/4 mark is 180 and top mark is 212. Check your temp with a good heated engine, top radiator tank, then the lower hose, this is water going in and water leaving the radiator. Also make sure you have a coil spring in your lower hose to keep it being sucked close over 30 MPH. Walt
Thanks Walt- I have the 3 piece lower hose(s) and metal tube setup and the two hoses are pretty beefy so I know that isn't the problem...I've come to the conclusion its an out of whack gauge. If I can dig up a different gauge , I'll hook it up right at the sender and see what happens. I know it isn't hot because it is not pushing anything out the overflow tube on the radiator. Terry
Might it not also be the sender?
I have tried both sending units that I have with the same result. They are both from 308 heads and there is that possibility that they are both bad. Then I thought, maybe the new wire I used from the sender to the gauge has more resistance creating a different reading. Or maybe I'm overthinking the problem. Getting under that dash isn't an easy task....especially with everything freshly painted and polished. I'll keep at it though. Terry
Here's what I came up with. I measured the resistance through the sending unit at Ambien temperature and got 176 Ohms. I then calculated the ratio between the temp differences I was getting and what it should be( I was getting 148 degrees at the center hash mark- it should be 160) and turned that ratio into the amount of resistance at the sender that I should have....I added a 10w 10 Ohm resistor and it works great- dead center at 158 degrees (as measured with the IR temp reader) at the sender. I had the resistor because I thought I needed it to excite the alternator when the tell-tale light wouldn't go out.( from information sent to me by Park W.) That turned out to be a bad alternator. For whatever reason, the resistance from the sender was slightly low or the gauge needed more resistance because of age...I have no idea...I just know it works. Terry
Terry, I did a very similar thing to get the Pacemaker gauge to read more accurately. At cruising it sits now just above the half way mark which gives reassurance all is OK. I did have to try two different resistors to get the result I now have and could try for more accuracy but it is close enough for now - I may revisit it when I have less on my to-do list.
Alistair, NZ
Alistair- I got my resistor through a company here in Minnesota called Digi-key for about two and a half bucks- you can get any type resistor/capacitor or any other electronic device through them. The one I had got me as close to spec as I think I could get without a whole lot of fuss. I gave it a good shakedown cruise today at 60 mph for about 50 miles and the temp needle stayed almost dead center the whole time. Terry
Alistair- I got my resistor through a company here in Minnesota called Digi-key for about two and a half bucks- you can get any type resistor/capacitor or any other electronic device through them. The one I had got me as close to spec as I think I could get without a whole lot of fuss. I gave it a good shakedown cruise today at 60 mph for about 50 miles and the temp needle stayed almost dead center the whole time. Terry
Leave a reply
