quote Garry in Tampa:
It will foul plugs if the thermostat sticks open and the engine runs too cold. This can happen if the water pump fails and the thermostat gets hot enough to blow out the expansion jell that it uses to regulate the opening. It should normally run around 145 degrees Fahrenheit. The thermostat used opens around 140 …
Garry makes an excellent point! Once again, don’t skip over the basics, simple stuff!