How to Fix a Leak in the Radiator of a 1990 Toyota Corolla

Even with a slow leak, losing all of the coolant in your 1990 Corolla can cause extreme overheating conditions, resulting in permanent engine failure and leading to costly repairs. Evidence that the leak comes from the radiator will be wet spots on the ground, on the coolant fins on the core, side tanks, or either the top or bottom sections of the radiator. Additional radiator connections should be checked to make a final determination of where the leak is coming from.

Instructions

A plastic overflow tank sits in a separate frame in the engine compartment.

Look for a puddle under the radiator after the car has been sitting or after being driven. Since the radiator holds pressure, the leak might be visible just after a hot engine shut down. A squealing noise or evidence of steam around the radiator points to a radiator leak. Once located, look directly upward and try to spot the location of a wet spot or tiny stream of coolant escaping from the radiator under pressure. Mark the suspect location with chalk.

Use a radiator pressure tester to determine the exact location of the leak. The pressure tester has a hand pump and a universal radiator cap. Twist the cap on and pump the system up, according to how much PSI (pounds per square inch) the radiator requires. Find the pressure rating on your radiator cap--it will indicate the exact pressure amount required. Look for dripping or squirting water. A hiss will indicate air escaping from a hole or crack. Mark the leak location with chalk.

Locate the two metal lines that lead from the engine to the inside bottom part of the radiator. Toyota Corollas with automatic transmissions have transmission coolant lines that run to the bottom of the radiator. They are attached with line fittings and large nuts that secure the transmission line to the fitting on the radiator. They do not carry coolant, only transmission fluid. Do not mistake transmission fluid for radiator coolant. Transmission fluid will appear as a brown or reddish color, and can be recognized by an oily feel and a petroleum smell. In this case, the transmission line fitting needs tightening and/or cleaning--it has nothing to do with coolant leaking from the radiator.

Inspect the condition of the radiator hoses. The upper and lower radiator hoses can be the source of leaks. Tighten the hose clamps where they meet at the inlet neck and return neck side of the radiator. Use a Phillips head or slotted screwdriver to tighten the hose clamps. If the leak persists from the hose connection, remove the hose end and use a wire brush to clean the connection neck. Thoroughly wipe the inside of the hose interior and reattach it.

Inspect the radiator cap for a bad ring gasket, allowing water to pass through it. Clean the cap interior and replace the gasket, then reattach and run the engine. Purchase a new cap if the leak persists. Cars equipped with plastic overflow reservoirs typically have a small hose that runs to the neck of the cap--examine this small connection for tightness.

Locate the overflow coolant reservoir. The coolant reservoir, a plastic water container, sits in a separate frame inside the engine compartment. It allows high-pressure overflow to return to the radiator. The plastic often cracks and dries out due to constant heat. Examine it for any external leakage. Apply epoxy glue to any leak source.

Inspect the radiator core for damage and leakage. Radiator leaks coming from the radiator itself mean the interior core is cracked or split, or the housing has failed. Rust causes deterioration in the core lines, regardless of the material they are made of--aluminum or copper. Mark the spot of the leakage with chalk. If the leak appears very small, a good quick fix requires adding a stop-leak additive to the coolant. The chemicals in the additive will forcefully clog the small opening. Heat-resistant epoxy glue works well to seal small holes. This is a temporary remedy but can last for quite some time before a permanent fix can be done.

Drain the radiator if the core is leaking. Core lines run vertically from the top of the radiator to the bottom. These thin, fin-like tubes hold water and dissipate heat by using free-flow air. To repair a core requires wire cutters to snip both sides of the leak location. Use pliers to roll up and crimp (tight) both ends of the core. This will stop the water flow through the core. Apply heat-resistant epoxy glue to the ends to ensure a complete seal. This procedure may require removal of the radiator to gain easy access to the leak location. In this case, remove the radiator by loosening the four mounting bolts, disconnecting the upper and lower radiator hoses, then disconnecting the transmission lines with a line wrench.

Place the radiator on a soft, flat surface. Having cut and crimped the leaking core, use a soldering gun to seal the ends of the core. Sand both crimped connections. With one hand pointing the gun, use the other hand to contact the gun tip with a segment of solder. Solder directly over the crimped connection. Melt several beads or globs of solder over the area. This gives added assurance to seal the leak.

Use a soldering gun to repair the leak on small- to medium-sized cracks or holes on the radiator housing. Sand the suspect area, using cross-hatching motions to prepare the area to be soldered. Run a bead or glob patch over the hole, working outward until a larger patch or line is applied. Any larger cracks, holes or splits in the radiator core housing will have to be repaired by a radiator repair shop. In the worst cases of damage, clogs or a rusted out core, the owner must purchase a new radiator to resolve the problem.