1993 Mercedes-Benz 400SEL Coolant Leak Diagnosis Cost

Repairing a coolant leak typically requires draining the engine coolant from the entire system, removing the faulty part, and either cleaning or replacing that component before reinstallation. Internal leaks tend to mean expensive repairs — a new head gasket or a new or refurbished engine being the most likely. Most often, though, repairing a leak involves a simple hose replacement and coolant flush.

On older vehicles, it's often recommended to flush the cooling system every two years or 30,000 miles. Many newer vehicles have extended-life coolant that can last up to 100,000 miles. It's always recommended to follow the service intervals in the owner's manual. Following the required services listed, whether it's a coolant change or coolant flush, will help ensure the longevity of the cooling system, as well as the rest of the vehicle. Outside of routine maintenance, coolant may need to be drained and replaced when repairing a cooling system leak. In that case, a full coolant flush should be performed if excessive corrosion is present, or if the factory scheduled service interval has already been passed.

The average DIYer can maintain the engine cooling system without much trouble, but diagnosing the point or cause of a leak can be tricky.  For instance, replacing a leaky hose is extremely low in difficulty. In contrast, replacing a water pump requires the removal of timing components and is not recommended for the DIYer. Don't use stop-leak products, as they can eventually cause clogs or contamination in the cooling system.