1961 Overheating Problems

[Greg Woods]

Hello everyone. My father and I are trying desperately to get out 1961 ready for a parade this Saturday. Problem after problem has arisen setting us back constantly, but we finally thought we were ready to go a few days ago. We were letting the car run, though, and we noticed it was getting very warm. Of course, the temp gauge does not work despite us sending the car to a wiring specialist (and me, prior to that, hooking a black resistor cable between the gauge and the wire that hooks to it [not sure of the name, but can anyone offer advice to get the gauge working again?]) so we had no idea what the engine running temp was, but the block was warmer than it should have been.

My dad and I had noticed a while ago that we had some leaks in the radiator, so we've since replaced that. Also, we've replaced the water pump and bought and installed a 160 thermostat. Despite this all, after 12 minutes of running (idling) it still shoots coolant from the fill tank. What could be some possible reasons for all of this? Moreover, how can we fix this and get the car to where it'll run in a four-mile parade (at parade speeds) by Saturday? (If the parade thing cannot be done, I'm fine with that, I just want the car to work.)

Thank you all!

[John H.]

Re: 1961 Overheating Problems

Greg -

I'd forget about the 4-mile parade until you have the cooling issue diagnosed, repaired, and verified. Go to the link below, scroll down to "cooling", and click on "cooling.pdf" (left-click to read, right-click to download) to understand your Corvette cooling system operation and diagnostics with facts, not misinformation.

Beyond the cooling issue, there's no duty cycle harder on clutches and throwout bearings than a parade; I gave up parade duty many years ago - changing clutches and throwout bearings gets old in a hurry.




Corvette Cooling System Facts

[Jim T.]

Re: 1961 Overheating Problems

First check for getting hot at idle rpms with all the changes you have done is to insure that all the air in the coolant system has been replaced with coolant. Next insure that your vacuum advance is advancing the timing 100% of the time, full time vacuum will help keep engine temp down in a parade. Vacuum advance units do fail.

[Jack H.]

Put science to work...

First, get a handle on the engine's actual temperature. Most widely recommended is to buy or borrow an IR, hand held, thermometer and shoot the bottom side of the upper radiator hose. Barring that, you can use the 'good ole boyo, roadside emergency check'...grab the upper rad hose with your hand.

It WILL be warm! But, since the human body is mostly water, anything hotter than 190-195F will cause your auto-response system to kick in and you'll release naturally. IF you can gut it out and hold the upper rad hose for a count of 3-5 without flinching, you can pretty much conclude the coolant temp is below that range (good!).

Next, if she really IS hot, it's time to put science to work and find out why. Most mechanics have a Stant pressure meter in their tool crib. There's an adaptor that allows you to remove and attach the radiator cap to the pressure meter. You hand pump it and watch/see how the cap holds pressure and at what point relative to the cap's rating it overloads and releases pressure.

Last, you remove the rad cap adaptor and put the pressure meter on the radiator in place of the cap. Fire up the engine and let it come up to temp watching the system pressure. If you have leak(s) in the system (pinholes in the radiator, poor hose connections, blown engine gaskets), you'll see pressure climb above normal operating level(s). It's time to go find/fix your cooling system leak(s)....