What to know about the Coolant Reservoir:

 Cooling systems on vehicles are intended to remove heat from critical engine parts. The fluid or coolant that circulates through the system carries the heat out of the engine to the radiator, where air flow dispels the heat it contains. A natural reaction to the heat which the fluid experiences is expansion. If the fluid in the cooling system is at the full mark when the engine is cold, the volume will be greater when the fluid is hot due to expansion. Because the cooling system is closed and pressurized when hot, the excess hot coolant needs to go somewhere. It is pushed into a surge tank, or an overflow tank, where it remains until the engine cools down. When the engine cools, the contraction from the fluid still in the system generates a vacuum and the surge tank’s hose draws the coolant back into the system. If the coolant surge tank is cracked or broken, the coolant will leak onto the ground. An airlock will form in the cooling system when the surge tank hose only draws in air instead of coolant.


Facts to Note:

Engine coolant is extremely hot when the engine is at operating temperature. By no means open the cooling system when the engine is hot.

The surge tank should be flushed when the coolant is being changed out.

How to Fix:

The coolant is drained into a suitable container and the coolant recovery reservoir cap is detached.


The old coolant recovery reservoir is disconnected from all of the hoses and pulled free of the vehicle.


The new coolant recovery reservoir is fixed into the vehicle and secured. The coolant hoses are fixed and secured using new clamps.


The coolant is refilled and purged of air as per manufacturer recommendation.


The vehicle coolant recovery reservoir is checked for leaks and proper operation.


Our Proposal:

The surge tank itself should never need attention unless it is spoiled or broken. Excess engine heat may also warp the container, though it is not common. If your coolant surge tank is broken or leaking, have one of your expert mechanics change it.


Common symptoms indicating you may need to change Coolant Reservoir:

Coolant leaking onto the ground when engine is hot.

Engine overheats due to an airlock.

Importance of this service:


The surge tank is part of the cooling system. It may seem to be auxiliary, but it is vital to proper operation. If the surge tank leaks coolant out, an airlock will form in the engine and it could overheat, causing damage. If your surge tank is damaged, have it changed as soon as possible to avoid further issues.