An engine temperature protection coolant bypass is a cooling-system upgrade designed to improve coolant circulation and help control temperatures in demanding diesel applications. For the 6.7L Cummins, coolant bypass systems are particularly focused on improving flow around the rear cylinders, where coolant temperatures can be higher.

Improve Coolant Flow

The rear cylinders of the 6.7L Cummins can experience reduced coolant flow. A properly designed bypass adds another coolant path, helping distribute coolant more evenly across the engine. Fleece Performance states that its system is designed to lower rear-cylinder temperatures and maintain more consistent temperatures across all six cylinders.

Some bypass systems use a secondary thermostat that opens according to coolant temperature. This approach is intended to increase flow before excessive cooling-system pressure becomes a problem.

Protect the Engine Under Load

An engine temperature protection coolant bypass can be useful for trucks that regularly experience demanding operating conditions, including:

• Heavy towing
• Long-distance hauling
• High-boost diesel builds
• Performance applications
• Extended engine loads
• Hot-weather operation

By improving coolant circulation at the rear of the engine, the system can help reduce temperature differences between cylinders and support more consistent cooling. Fleece also states that its 6.7L Cummins bypass is intended to help prevent damaging coolant-pressure buildup associated with rear-cylinder cooling issues.