I tried it with ballons. It works I just blocked the overflow it works. some inflaction is from steam or hot water but a blown head gasket will really inflate the ballon.
Here's a really cool trick an old-timer taught me.
Disclaimer! I've never had the chance to try it yet, so I don't know if it works. But I can't see why not!
Basically I was told to wait until the engine is cold, then pull off the radiator cap. Place a balloon (condom may work better) over the filler. Slide the balloon over the vent spout or block the vent hose/spout.
Now start the engine and let it idle for a couple of minutes. If you see the balloon inflate then you have a head gasket leak. Keep in mind, that the balloon will inflate as the coolent gets hot even if there is no headgasket leak. So the idea is to only run this test until the coolent starts to get warm.
I tried it with ballons. It works I just blocked the overflow it works. some inflaction is from steam or hot water but a blown head gasket will really inflate the ballon.