How to Fix Coolant Reservoir Tank Leaks

by Jody L. Campbell

A coolant reservoir is a dual-purpose component. It provides the extra coolant the radiator and cooling system need in the event of a leak and prevents overheating. Usually filled to one-third of it's capacity, the coolant reservoir provides storage for coolant when the radiator purges coolant as it heats up. When the system cools down, the radiator pressure reverses and coolant is siphoned from the reservoir back into the radiator. A cracked or leaking reservoir can easily be diagnosed and fixed. Removing it and whether the fix will hold up under the average 15 psi pressure may impose challenges and risks to question the validity of the repair.

Step 1

Remove any remaining fluid from the coolant reservoir using a siphon hose and a drain bucket.

Step 2

Circle the area of the leak with a marker or crayon once established.

Step 3

Relieve the pressure from the radiator by removing the cap. Some models place the pressurized cap directly on the reservoir, so make sure the system is cool before attempting to repair.

Step 4

Disconnect the overflow tube that runs from the reservoir to the radiator. Most applications employ a small ring clamp that a pair of pliers can expand and then slide the clamp further down the tube. Twist the tube gently back and forth to remove it from the reservoir nipple.

Step 5

Disconnect any retaining screws, bolts or straps holding the reservoir tank in place. In some models, you may have to remove additional components to access and then remove the tank.

Step 6

Dump the remainder of the coolant in the reservoir that the siphon was unable to remove into the drain bucket.

Step 7

Rinse and clean the interior and exterior of the reservoir with a water hose, taking note where the crack or leak is in the event your marker or crayon washes away. Allow the reservoir to dry thoroughly.

Step 8

Mix the plastic weld or epoxy according to the directions on the label. Most plastic welds or epoxy welds need to be mixed and allowed a curing time for the chemicals to combine. Once the welding compound has been given enough time to set, spread it out along the crack or leak on the reservoir using an applicator. Be sure to fill in an crack by pressing the epoxy into it with the applicator. Allow the epoxy or plastic weld time to dry. On many plastic or epoxy welds, this can take up to 24 hours to dry properly.

Step 9

Replace the tank and any other components that had to be removed, if applicable.

Step 10

Replace the coolant from the drain bucket back into the reservoir and then fill it to the full line indicator. Retest the system under pressure using the radiator pressure tester.

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