[Richard]

The original simple green was very caustic. I havent looked at the “citrus” based simple green. I would not use simple green, purple power, or any big box store branded degreaser. Most are powerful caustics .

Clint is spot on. Use Dawn at about 25% dilution and let it soak.

Degreasers like Gunk have strong petroleum solvents. They wont hurt your radiator but they will kill allnthe rubber hoses