Q: Frozen water in the reservoir instead of antifreeze

Hi there:

Most of the time, when the coolant overflow reservoir freezes up due to water being put inside, it can cause cracking; since they are typically made of plastic. The best thing to do is to remove the bottom return line from the reservoir and flush it with room temperature water until the ice is completely removed. Once that’s been done, replace the overflow hose, fill up with water first to check if there are any leaks. If it does not leak, flush all water from the reservoir, and completely flush the radiator fluid from the system. Refill with 50/50 ratio of coolant to distilled water. If the reservoir leaks, you’ll have to replace the coolant overflow reservoir.