3 cyl diesel tractor

Tractor JD, is forcing coolant past radiator cap and out over flow tube. I suspect head gasket. Have changed cap, etc. Engine does not run hot in cooler fall temperatures , but will get very near the hot indicator in hot summer months. Thermostat is not the problem.

I know the correct repair is replace head gasket, but is any of the pour in head gasket sealers any good, Blue Devil is one that I have heard was a favorite.

Really appreciate comments. Don't want to make matters worse.

I wouldn't use any pour in sealer. My cousin had also heard good things about Blue Devil and followed the instructions to a tee. He ended up replacing his entire cooling system as well as his head gasket as a result.

Thanks