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Honda Civic Radiator Overflow Tank

How to Diagnose Problems with the Honda Civic Radiator Overflow Tank

The overflow tank is an important part of a car's cooling system. It stores any extra coolant overflowing from a hot radiator. As the radiator cools down, the coolant inside it will contract, creating a vacuum that sucks the coolant in the overflow tank back into the radiator. This ensures that no coolant is wasted and that your radiator won't be left dry. Unfortunately, problems may occur with the overflow tank, and they need to be fixed immediately. To help you out, here are some common Honda Civic radiator tank problems you should know of:

Significant decrease in coolant level

If you find yourself adding coolant to the overflow tank often, you may have a leak in the cooling system. Check the overflow tank first for any sign of damage. If the overflow tank is in excellent condition, the leak may be from the radiator, the coolant hoses, or within the engine. Survey the bottom of the Civic and check if there is any puddle of coolant. If you see such puddle, the source of the leak could be directly above it. Trace the source of the leak and apply the appropriate fix.

Damaged overflow tank

Damage to the overflow tank should be fixed immediately. Inspect the overflow tank before doing anything; if the damage is relatively small, trying using plastic or epoxy welds to seal it shut. Be sure to follow manufacturer instructions closely and give the epoxy time to cure and dry up before reinstalling the overflow tank. If the overflow tank is old, then the damage is probably caused by wear. Replace the whole tank in that case. Remember that any fix you might try on an old overflow tank will only be temporary; chances are, it will break again in the near future. For extensive damage, replacing the whole thing should be a no brainer.

Coolant not being sucked in from the overflow tank

You can check for this condition by inspecting the coolant level in the radiator. Be sure to check your radiator after the Civic's engine has thoroughly cooled down. If there is a decrease in the radiator's coolant level even if the coolant in the overflow tank is left untouched, then air must be getting in the radiator from some other point. The first thing you should check is the radiator cap. Replace it with a new one and see if that solves the problem. Check the hose connecting the overflow tank to the radiator and be sure that no leak is present. Other parts you should also check are the rest of the cooling system hoses and the radiator.

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  • Keep Cool With Honda Civic Radiator Overflow Tank Maintenance Tips

    Overflow tanks, or coolant recovery systems as they are known, store coolant that is ejected from a radiator. As the radiator cools down, the coolant gets sent back into it. This makes the overflow tank a rather important part of the Civic's cooling system. To ensure the smooth operation of this system, you will need to keep the overflow tank in working order. Here are some important Honda Civic radiator overflow tank maintenance tips to follow:


    Top off the overflow tank with the correct coolant and water mixture.


    With the invention of the overflow tank, opening the radiator has become unnecessary except during a complete radiator flush or other extraordinary circumstances. If you only need to add a small amount of coolant to the cooling system, add it to the overflow tank instead. Be sure the mix has the correct water/coolant ratio, which is usually about 1 part coolant and 1 part water. Manufacturer recommendations may vary a bit so be sure to read the appropriate instructions with regards to coolant use. The overflow tanks of your Honda Civic will have a level indicator in it showing the recommended minimum and maximum level of the coolant. Be sure you fill the coolant up to any point between both of those levels.


    Check the coolant level in the overflow tank frequently.


    Before driving off to work in the morning, take a look at the coolant level inside of your Honda's overflow tank. Such frequent inspections will allow you to find any problem with the overflow tank or the cooling system early on and allow you to fix them; this is a much better prospect than having your car overheat in the middle of the highway. The coolant level may decrease noticeably every few weeks or so but don't let that bother you. Just top off the coolant and you'll have no problem. If the coolant level starts to decrease more than normal, you will need to have the overflow tank or the other parts of the cooling system checked for possible leaks.


    Fix any leak you'll find in the overflow tank immediately.


    If you discover that coolant is leaking from your overflow tank, be sure to fix the situation immediately. Small holes and minor damage to the overflow tank can be fixed with a plastic mending kit or some epoxy. If the overflow tank is pretty old or if the damage to the overflow tank is big, it's better to replace the tank with a new one instead.