How to Repair a Car Radiator Leak

A radiator is an essential part of an automobile's liquid cooling system that must function properly to prevent the engine from overheating. A leaky radiator can lead to a costly mechanical meltdown, so it's important to discover and repair this problem as soon as possible.

1
Look for signs of coolant leakage on the garage floor, driveway or ground under your vehicle.
2
Check the level of coolant in the overflow reservoir or inside the radiator by removing the radiator cap. The engine must be cool before the radiator cap can be safely removed. If the coolant level in the overflow reservoir or radiator is unusually low, odds are good that you have a leaky car radiator.
3
Inspect the radiator to find where it is leaking. There may be an obvious hole or other defect that is easy to spot, such as deposits of coolant and an orange or green discoloration.
4
Remove the radiator for further testing if the leak cannot be found.
5
Use a radiator pressure test kit to fill the radiator with the amount of air specified by the radiator cap. Submerge the radiator in a tank of water and watch for escaping air bubbles. The source of these bubbles is the leak that must be repaired.
6
Pour the stop-leak additive into the radiator to fix small leaks, following the instructions on the product label.
7
Use a soldering iron to patch larger defects in radiators made of copper and brass, which are frequently found in older models. An epoxy gun may do the trick for the aluminum radiators in newer vehicles.
8
Refill the vehicle's cooling system after the radiator leak is repaired.