So I just recently started getting my coolant to boil over. My temp gauge never overheats, and I just had the radiator, clutch, and thermostat changed to possibly fix it. The coolant has been tested for a blown head gasket, and it passed. Threw on a new coolant cap, and just about got all the air out of it. It’ll start to boil when I’m driving, and when I’m done driving, it’ll overflow. What else could I be missing?
I’m still betting it’s a bad head gasket, the coolant isn’t boiling, it’s bubbling as the exhaust gasses are pushed through it. Or it’s air trapped. Did you have the system pressure checked?
You can get a kit like this:
to rule out HG exhaust leak into the coolant.
If it has an automatic transmission, check the color/smell of the fluid.