Need help troubleshooting an overheating indication. Does anyone know what the correct temperature sender resistance range is supposed to be to work with a stock temperature gauge? I suspect I might have the wrong sender unit installed in my restored engine but have no specs to follow. I found a 25 kOhm resistor wired to the temperature gauge but do not see this in any of the wiring diagrams, but when I remove it indicates even hotter (full scale hot). My 1958 Chevy Apache 3100 has its stock 235 engine which was recently restored but it shows that it runs hot whenever I stop at a couple of traffic lights or let idle for any length of time, runs in the middle of the indicator range whenever I'm moving. I have added a shroud, checked the thermostat and water pump and correct coolant levels, all checks good. Also, it does not port anti-freeze, so I am not sure I am actually overheating. Any tips, data or suggestions would be greatly appreciated.
RE: Stock temperature gauge/sender You can still buy a temp sending unit for your truck and if you have the correct unit the resistance should be correct. Since it heats after idling it should be easy to check the actual temp with any thermometer that goes to 212 degrees. Stant used to make a thermometer that fit where the radiator cap goes, even had a little chain that you picked it up with after it got hot. Be sure to leave the cap off during heat up time so you won't have to remove it from a hot radiator. For checking when driving you could get a "cheapo" under dash mechanical guage and temporarily clamp it under the dash. I sure wouldn't leave it cause they look like crap. I still like the 55 guage-- they went to electric in 56 but they interchange. Good Luck
RE: Stock temperature gauge/sender Thanks for the great tips. I happen to have bought an old instrument cluster from eBay that has a mechanical water temperature gauge. I will try to get the sender and capillary tube for it and install. In the meantime I will try the temporary gauge route. Will post once I figure out what was really happening!
RE: Stock temperature gauge/sender I had a simuler problem with my new overhauled 235 I bought a sending unit form Chevy Duty and one from NAPA and both peged out after a few minutes of running, after several changes of sending units and dash units combo's I found a used sending unit in an old 283 engine and it solved my problem, so you might try the junk yards for an old engine?? please excuse the spelling. Billy Gibson
RE: Stock temperature gauge/sender One should always check the accuracy of the temperature gauge. Here is a good article (link) about how to check. This is as true for new in the box gauges as for old or salvaged gauges. http://www.madelectrical.com/workshop/water-temp-gauge.shtml John
RE: Stock temperature gauge/sender 1958 Chevy Apache 3100 Thank you for the information. The page you provided was very informative and will try some of the techniques mentioned. I have been busy for a while and have not gotten back to the forum, but since my post I have added a shroud, replaced the original fan with a flex fan and spacer to put fan closer to radiator retuned engine and added an after market Sun temperature gauge with a new matched sender. Unfortunately I still get a large temperature rise after 5-10 minutes at idle or in sto and go traffic! I will verify the accuracy of the gauge before any additional work and let all know what my progress is.
RE: Stock temperature gauge/sender This may sound really weird,but my 383 stroker would peg out the temperature gauge as I watched after 3 minutes of driving.It would rise to the top and fall after the thermostat opened.the solution I got from a radiator specialist,who told me that my problem was air in the system that didn't let the hot water touch the thermostat so that it would open. He then told me to drill a 1/16 in hole in the thermostat so that the air in the system would easily bleed by the thermostat-and presto-no problem!I was also told that such a thermostat with a bleed hole exists,so it may not be necessary to make one!
