Radiator Leak Repair Cost: $150 to $400

The most common failure on modern vehicles. Plastic end tanks are crimped onto the aluminum core with a rubber gasket. Heat cycling makes the plastic brittle over time. Cracks typically start at stress points near the mounting brackets or the inlet/outlet connections. Plastic tanks cannot be reliably repaired. Epoxy patches on plastic tanks rarely hold under system pressure and temperature cycling. If the tank is cracked, replacement is the right call.

The joints where individual tubes connect to the header plate can develop leaks from vibration and thermal stress. On aluminum radiators, a specialty shop can sometimes braze or epoxy a single joint. On copper/brass radiators, soldering is straightforward and durable. Cost: $100 to $250 at a radiator specialty shop.

Corrosion from the inside out eats through individual tubes, creating pinholes. A single pinhole on an otherwise sound radiator can be fixed with epoxy or by crimping the tube ends (sacrificing that tube's cooling capacity). Multiple pinholes mean the corrosion is systemic and the entire core is compromised. At that point, further pinholes will keep appearing and replacement is the only lasting solution.

The drain valve at the bottom of the radiator can crack or strip over time. Replacement petcocks cost $5 to $15 and take minutes to install. Before assuming a radiator leak, check whether the drain valve is seeping. This is the best-case scenario for a coolant puddle.

The rubber gasket between the plastic tank and the aluminum core hardens and shrinks over time, allowing coolant to seep at the seam. Some shops can re-crimp the tank with a new gasket ($150 to $300 in labor). Others will recommend full replacement because the plastic tank is often close to cracking if the gasket has already failed. Get two opinions if the quote jumps straight to replacement.