Radiator issues

Several years ago my '63 Valiant had some overheating issues, which I resolved with some stop-leak. This weekend, feeling neglectful, I washed her, added a quart of oil, and added some premixed coolant. That evening when I drove it, it overheated. I know, if it ain’t broke, don’t fix it, but now what do I do? It’s obviously lost coolant. I’m leaning towards putting more stop leak and more coolant, but I don’t want to make things worse. I’d rather not have to replace the radiator right now, but I will if I have to. Any suggestions?

Nice thing about those old radiators was that you could solder them up yourself. You need to pinpoint the leak first though. Could it be a heater hose?

No more stop leak.
Too much will stop the flow where it’s supposed to be going.
Now it’s time to fix the leak or replace.
Have you seen the actual leak ?

Fair warning, I’m kind of a dolt when it comes to cars, even one as simple as mine. Could my putting extra coolant in have put too much pressure on it and overloaded the system? When it was overheating a few years ago, I was told that the radiator was too far gone and I needed a new radiator but could try stop leak first, which worked beautifully. I could have someone look at the heater hose also. I’m just not sure what to do first.

First, the additional coolant didn’t hurt. Second, you may not have a leak. At least, you never mentioned actually seeing a leak.

Overheating can be caused by a number of factors such as a bad thermostat or water pump. But if you find a visible leak, then that something needs to be replaced.

Check it yourself. If you don’t see anything obviously wrong, it’s off to the shop you go.