How to Fix a Leaky Radiator Expansion Tank

car Radiator
  • 2-3 hours
  • Beginner
  • 35-75
What You'll Need
Replacement Expansion Tank
Socket Set
New Coolant
What You'll Need
Replacement Expansion Tank
Socket Set
New Coolant

The radiator expansion tank is an important part of your car's cooling system. This is a vessel that allows the water and air inside the sealed system to expand due to an increase in temperature. Over time, these expansion tanks can leak. It might be better to replace the leaky radiator expansion tank with a newer tank.

Step 1 - Checking for Leaks

You should be checking the level of coolant in the expansion tank every other time you fill up with gas. If you notice that the level of coolant is significantly dropping very quickly, there is probably a leak. A leak can affect the cooling systems ability to cool down your engine.

Step 2 - Allowing the Engine to Cool

First you need to give your engine plenty of time to cool down so that it's safe to work on. The radiator and expansion tank in your car can get very hot and not allowing them to cool before working on them can be very dangerous.

Step 3 - Draining the Coolant

Before removing the radiator expansion tank it's a good idea to empty the coolant out of the system. You should be able to find out how to do this by looking in your car owners manual. It's normally a matter of opening a drain valve or disconnecting one of the pipes from the tank and allowing the coolant to flow out.

You may as well use the opportunity to replace all of the coolant in your system. Make sure that the coolant is disposed of carefully: pour it into a plastic bottle and throw it away. Never tip it down the drain as it can contaminate ground water supplies.

Step 4 - Disconnecting the Tank

The radiator expansion tank will be connected with a series of pipes. If you haven't already disconnected these to drain the tank, do so now.

Step 5 - Removing the Tank

The radiator expansion tank is normally bolted into the space under your hood. Use the socket set to undo the bolts so you can lift the tank out of the car.

Step 6 - Replacing the Tank

Now you can fit the new tank into the same place. Make sure that you use the same type of expansion tank to make this very easy. Once you have fitted it into the space, bolt it back into place.

Reconnect the hoses and fill up the expansion tank with new coolant. Once everything is connected, check for leaks. Then turn your engine on and check that the radiator is keeping the engine at the correct temperature.