What causes coolant to back up in reservoir?

Coolant, or antifreeze, is essential to regulating the temperature of your vehicle. It’s also extremely toxic and designed to stay inside a closed system. If you’re seeing an overflow, it could be due to a radiator cap, thermostat, water pump, or radiator malfunction.

Why do you need to fill the radiator if you have a blown head gasket?

It’s not out of the question at all @ 125K that you have a blown head gasket. You need to fill the radiator because (as has been explained) gases from the engine are getting into the coolant system, which’ll cause bubbles.

Why does a bad head gasket cause the coolant reservoir to?

Your head gasket is allowing high pressure combustion gasses into the low pressure cooling system. These gasses are displacing the water in the cooling system. There isn’t room for the gasses and the water, so the water gets pushed out. It’s as simple as that.

Can a faulty radiator cap cause coolant to overflow?

A faulty radiator cap can cause the coolant reservoir to overflow and overheating the vehicle’s engine system. If the radiator hoses are always transporting hot fluid, then the hoses will wear out and will finally tear.

What does it mean when your Radiator reservoir is full?

Suppose you notice that your radiator is empty, but your coolant reservoir tank is full. In that case, it might mean that there is or there are few damages in the components of the engine cooling system, which means that there is possibly a faulty radiator or radiator hose, a damaged gasket, or a radiator cap, or some other faulty components.

Your head gasket is allowing high pressure combustion gasses into the low pressure cooling system. These gasses are displacing the water in the cooling system. There isn’t room for the gasses and the water, so the water gets pushed out. It’s as simple as that.

It’s not out of the question at all @ 125K that you have a blown head gasket. You need to fill the radiator because (as has been explained) gases from the engine are getting into the coolant system, which’ll cause bubbles.

Suppose you notice that your radiator is empty, but your coolant reservoir tank is full. In that case, it might mean that there is or there are few damages in the components of the engine cooling system, which means that there is possibly a faulty radiator or radiator hose, a damaged gasket, or a radiator cap, or some other faulty components.

A faulty radiator cap can cause the coolant reservoir to overflow and overheating the vehicle’s engine system. If the radiator hoses are always transporting hot fluid, then the hoses will wear out and will finally tear.