The intercoolers serve the purpose of reducing the temperature of the compressed air flowing out of the turbocharger or supercharger. Over time, the intercooler inlet hoses or outlet hoses may be subjected to breaks, cracks or corrosion, resulting in leakage of air. This air leak will affect the overall efficiency of the engine. Some of the common symptoms of a defective intercooler include decreased engine efficiency and engine detonation. Due to detonation, combustion process may leave unburnt fuel residue. This can emit a strong odour of gasoline. Otherwise, detonation also causes a pinging or knocking noise. A periodic inspection of the intercooler can prevent costly repairs for it in the future. Generally, intercoolers need to be cleaned every 10,000 to 15,000 miles or as recommended in the owner's manual. If you are using a water-based cooler, check for the optimal level of water periodically. While replacing a damaged intercooler, it is always a wise decision to replace the associated parts including the inlet hose and outlet hose.