C1 RADIATOR CAP

[Joe D.]

I have a top tank radiator in my 61. I bought an original style cap from Dewitts. My car is running very hot. Replaced sending unit, thermostat. Temp gauge is pegged after five minutes. Can I use any type of 13lb GM cap? The replacement cap seems kind of cheap. It is very thin. Thanks for the help, Joe

[Stephen B.]

Re: C1 RADIATOR CAP

I do not believe the cap has anything to do with an overheat in 5 minutes of running . is this stopped in your driveway . could be a clutch fan problem .5 minutes seems awful quick for an overheat condition , is it burpping coolant on the ground ? maybe a check with an infared thermometer is in order just my 2 cents Steve

[Joe D.]

Re: C1 RADIATOR CAP

I just got my car back from paint last week. They started it up and told me about the heating problem.It was towed back to me. I have not driven the car for fear of getting stuck. It does not puke. He put a thermometer in it and said it was around 190, but the gauge was pegged. He did not sound too sure that it was safe to drive. I was hoping to get the gauge to read correct before I drove it. Thanks

[Wayne P.]

Re: C1 RADIATOR CAP

It's not TOO hot at 190. Sounds like a sending unit gauge mis-match. Did you have this problem before it went to the shop?

[Harry Sadlock]

Re: C1 RADIATOR CAP

Joe, if it's easy with your C1, remove the gage and the sending unit and have them tuned together. Meaning, you can set the temp at the sending unit, say 180, them move the needle on the gage to 180. Then change the temp of the sending unit and ensure the gage follows. I know JR of Joe Ray Parts provides the service if you can't do it. It could be a combination of a bad sending unit and an offset needle on the gage.

This is what I did on my C2, I just assume a C1 is the same with respect to the temp, gage.

Harry

[Joe D.]

Re: C1 RADIATOR CAP

Not befor the engine was rebuilt.I have a new radiator also. Thanks, Joe

[Joe D.]

Re: C1 RADIATOR CAP

I just replaced the sending unit with one from Corvette Central which is suppose to be corectly calibrated. In a matter of minutes the ghauge was burried. Thanks, Joe

[Michael K.]

Re: C1 RADIATOR CAP

I put a new aluminum radiator from Dewitts in my 57, so I thought I would replace the temp sending unit. I purchased one from Doc Rebuild. It buried the temp guage in a matter of minutes. The engine was not overheating! I put the original sender back in, problem solved. CC sells a variable resistor so that you can adjust the voltage to the guage.

[Joe D.]

Re: C1 RADIATOR CAP

Rick, I think I will try that. Thanks,Joe

[John H.]

Re: C1 RADIATOR CAP

Joe -

Note that the variable resistor inserted in the sender circuit at the gauge will ONLY calibrate the gauge for accuracy at the engine temperature you choose as your calibration point (using an I.R. gun on the radiator hose just above the thermostat housing), and the gauge will be inaccurate above and below the calibration point you select; the response curve for the thermistor in the sending unit isn't linear to begin with, and adding resistance to that circuit just makes it less so.