Coolant Bypass Hose

Why Does Your Truck Need a Coolant Bypass Hose?

A coolant bypass is not a luxury add-on. It is the difference between a cooling system that holds pressure and one that empties itself on the side of the road. These are the three failures that push shop owners to call us.

Rear Freeze-Plug Blowouts on 5.9L and 6.7L Cummins

The stamped steel cup plug at the rear of the Cummins block sits hidden behind the transmission, bathed in hot coolant for years. Cast iron plus neglected coolant rusts that plug from the inside until it pushes out and dumps the entire coolant charge in seconds. The billet bypass plug and freeze kit seal that bore with a high-temperature Viton O-ring so the plug cannot walk out under load.

Thermal-Cycle Fatigue on Molded Rubber Bypass Hoses

Heat, ozone, and constant pressure cycling crack and collapse factory molded rubber over time. A bypass hose that has gone soft or split internally restricts flow, spikes temperature, and finally ruptures at full operating pressure. The reinforced EPDM crossover in this collection resists collapse and holds its shape through years of heat cycling.

Restricted or Dead-Headed Coolant Flow in LS Swaps

When you delete a heater core or reroute a steam vent during an LS swap, a wrong-length or pinched hose dead-heads the circuit and starves circulation. The molded U-shape crossover bridges the two ports cleanly so coolant keeps moving instead of boiling in a trapped pocket behind the intake.

What Can a Coolant Bypass Hose Solve?

Each component here targets one specific leak or flow problem instead of papering over it with a generic rubber loop.

Seals the Cummins Rear Block Bore

The CNC-machined 6061-T6 billet plug and brass barb adapter replace the failure-prone cup plug with a leak-proof barrier sealed by a high-temperature Viton O-ring, then route a controlled bypass line off the barb.

Restores Coolant Circulation on LS Builds

The molded EPDM U-shape crossover bridges the heater core and steam-vent ports so coolant circulates through heater-delete and swap builds instead of dead-heading against a blocked outlet.

Holds System Pressure Without Weeping

Aramid-fiber reinforcement and T304 stainless clamps let these hoses and fittings hold 18 psi of hot coolant without splitting, collapsing, or seeping at the seal.

Shop Coolant Bypass Hose by Cummins & LS Engine Fitment Guide

• Coolant Bypass Hose Barb Adapter Kit - Fits 6.7L Cummins in Dodge Ram 2500 3500 (2009-2019). CNC-machined 6061-T6 billet plug with a high-temperature Viton O-ring and brass hose barb replaces the failure-prone rear block cup plug and routes a clean coolant bypass line on the 6.7 high-pressure common-rail.
• Freeze Coolant Bypass Kit - Fits 5.9L and 6.7L Cummins in Dodge Ram (2003-2018). Full billet aluminum freeze-plug bypass kit seals the rear block bore behind the transmission and restores a leak-proof coolant barrier on both the 24-valve 5.9 and the newer 6.7.
• Coolant Bypass Hose Barb Adapter Set - Fits 6.7L Cummins in Dodge Ram 2500 3500 (2009-2019). Billet barb adapter set threads into the rear block location with a Viton O-ring seal and accepts the bypass hose for trucks running the 6.7 common-rail.
• U Shape Heater Core Bypass Crossover - Fits 4.8 5.3 5.7 6.0 6.2 LS1 LSX LS2 LS3 LQ4 LQ9 in GM trucks and LS swap vehicles (1999-2013). Molded EPDM coolant crossover reinforced with aramid fiber and clamped with T304 stainless bridges the heater core and steam-vent ports for LS swap and heater-delete builds.

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What is a coolant bypass hose and what does it do?

A coolant bypass hose reroutes engine coolant around a blocked, deleted, or relocated cooling circuit instead of letting it dead-head or leak.
On a 5.9L or 6.7L Cummins the bypass hardware replaces the rear block freeze plug with a CNC-machined billet plug and a hose barb, so coolant flows through a controlled line rather than a rusted cup plug.
On an LS engine the molded crossover bridges the heater core or steam-vent ports during a swap or heater delete. The goal is simple: keep coolant moving through a fitting you can trust instead of one about to blow out.

Why do 5.9L and 6.7L Cummins engines need a coolant bypass kit?

The rear block freeze plug on a Cummins sits hidden behind the transmission, and it is a chronic failure point.
Cast iron plus old coolant rusts the stamped steel cup plug from the inside until it pushes out and dumps the entire coolant charge in seconds.
The billet aluminum bypass plug and freeze kit seal that bore with a high-temperature Viton O-ring so the plug cannot walk out. We install these on every heavy-tow Cummins we service, because a roadside boil-over at full load can cost you a head gasket.

What LS engines does the U-shape heater core bypass crossover fit?

The molded U-shape crossover fits Gen III and Gen IV LS V8 engines, including the 4.8L, 5.3L, 5.7L LS1, 6.0L LS2 and LQ4, and 6.2L LS3 and LQ9, plus LSX builds.
That covers the 1999 to 2013 GM truck engines and the LS1 Camaro, Firebird, and Corvette platforms.
It is built for LS swap builds and heater-core-delete setups that need to bridge the two coolant ports and bleed the steam vent. Confirm your intake and water-pump layout before ordering, because accessory-drive and steam-pipe routing varies across LS platforms.

Will the LS crossover work as an LS swap throttle body coolant line or water pump bypass?

This collection carries the U-shape heater core and steam-vent crossover, not a dedicated LS throttle body coolant bypass hose.
The throttle-body preheat circuit on an LS1 or Gen III truck engine is a separate small line, and many builders delete it to drop intake air temperature.
There is no standalone throttle body bypass hose or water pump bypass pipe in this catalog, so if your build needs that exact routing, confirm the part before ordering. The crossover here handles heater core and steam-vent coolant only.

Does this collection have a coolant bypass hose for a 2015 Chevy Cruze?

No, there is no Cruze coolant bypass hose in this collection.
The 2015 Cruze runs the GM 1.4L turbo engine, and its heater hose bypass carries OEM numbers such as 13251447 and 13408385, which is a completely different platform from the Cummins diesel and LS V8 parts listed here.
We do not carry that Cruze bypass hose and we would not want you to order the wrong fit. For the 1.4L turbo bypass line, check with your GM dealer or a Cruze-specific supplier for the correct molded hose.

Do you carry a radiator bypass pipe or water pump bypass pipe?

This collection is focused on the Cummins rear freeze-plug bypass and the LS heater core crossover, so there is no radiator bypass pipe, water pump bypass pipe, or coolant bypass tube listed here.
Those terms describe different cooling-system routing on other engines and platforms.
We do not stock a generic radiator hose bypass or water pump bypass pipe in this collection, and we will not guess a fitment that is not here. If you need one of those pipes, confirm the exact engine and routing with the right supplier first.

Can I use the heater hose bypass to delete or loop my heater core?

Yes, on an LS engine the U-shape crossover is exactly what builders use to loop or bypass the heater core in a swap, a race car, or a deleted cabin-heater setup.
The molded EPDM hose bridges the two ports so coolant keeps circulating instead of dead-heading when the heater core is removed.
The Cummins barb adapter kits serve a different purpose, which is sealing the rear block bore and routing a clean bypass line off the freeze-plug location. Match the bypass to your engine: LS for heater-core loops, Cummins for freeze-plug protection.

What materials are these coolant bypass parts made from?

The Cummins plugs and barb adapters are CNC-machined from 6061-T6 billet aluminum, hard-anodized for corrosion resistance, and sealed with a high-temperature Viton O-ring at the block bore.
The LS crossover is a molded EPDM coolant hose reinforced with aramid fiber to resist collapse under system pressure, finished with T304 stainless steel clamps.
Every fitting is precision-machined and pressure-tested, not a stamped parts-store cup plug or a generic rubber loop. That material package is what holds 18 psi of hot coolant without weeping.

How hard is it to install the Cummins freeze-plug coolant bypass?

On a 5.9L or 6.7L Cummins the rear block plug sits behind the transmission, so the cleanest access usually means pulling the transmission or working from underneath on a lift.
The billet plug threads or seats into the block bore with the Viton O-ring already lubed, and the barb accepts the bypass hose with a T304 stainless clamp.
It is a precision fitment job, not a driveway quick-fix, and most shops pair it with a coolant flush while the system is open. If you are not set up to reach the rear of the block, this is one to hand to a diesel tech.

Are coolant bypass hoses and fittings street legal?

As cooling-system repair and upgrade parts, these bypass hoses and billet plugs are direct-fit replacements that do not remove or bypass an emissions device, so they are street-legal for daily-driven Cummins and LS trucks.
On competition, race, and tuned or deleted builds, this hardware is intended for competition and closed-course off-road use only, and local emissions and equipment laws vary by jurisdiction, so confirm your fitment and your local rules before ordering.
Every order includes free shipping, is backed by a 1-year warranty, and comes with our 45-day return policy. We supply the hardware and the fitment guidance, and you are responsible for checking how your build is regulated where you drive.