Mailbag: The Difference Between Single-, Double-, and Triple-Pass Radiators

Q: What is a double-pass radiator?

…

A: In a single-pass radiator, coolant only crosses the radiator core one time.

1. Fluid enters the inlet.
2. It flows across the core in tubes.
3. It is collected in the opposite side tank.
4. It exits the outlet and flows through the system again.

Single-pass radiators work well in most street applications. For stock and mildly modified engines, they provide adequate cooling.

Replacing a single-pass radiator usually requires no modifications. The inlet and outlet will be on opposite sides of the radiator. Also, your stock water pump can handle the flow requirements.

Double-Pass Radiators

A double-pass radiator is divided in half. Coolant crosses the core twice.

1. Fluid enters the inlet.
2. A baffle inside the tank directs incoming fluid across the top half of the core.
3. The fluid collects in the opposite side tank.
4. It flows back across the core on the bottom half.
5. It exits the outlet and flows through the system again.

A double-pass radiator is considered an upgrade over a single-pass. All else being equal, a double-pass radiator can increase cooling efficiency 5-10 percent. It works well in both street and race applications.

Replacing a single-pass radiator with a double-pass will require some modifications. The inlet and outlet will be on the same side of the radiator. So, custom hoses may be required. Also, a high-volume water pump is recommended.

Triple-Pass Radiators

A triple-pass radiator is exactly what you think. Coolant crosses the core three times.

1. Fluid enters the inlet.
2. A baffle inside the tank directs incoming fluid across the top of the core.
3. A baffle in the opposite side tank directs the fluid across the middle of the core.
4. The fluid collects in the opposite side tank.
5. It flows back across the core on the bottom.
6. It exits the outlet and flows through the system again.

A triple-pass radiator works best with highly-modified race engines. High horsepower and power adders require more cooling capability.

Depending on the specific application, a triple-pass radiator can increase cooling efficiency 10-20 percent. A triple-pass radiator is probably overkill for most street vehicles.

The triple-pass design will have the inlet and outlet on opposite sides. A high-volume water pump and a 1-to-1 pulley are usually required to ensure proper flow.

NOTE: For best radiator performance, always use the proper cooling fan and fan shroud.

…

This is another in a series of weekly Q&A Mailbag sessions with Summit Racing‘s tech department, in which there are hundreds more. Click here to see them all.