Heater Outlet Pipe Coolant Leak

A coolant leak or coolant smell at the front passenger-side of the vehicle may be noticed on some 2019-2021 Silverado 4500HD/5500HD/6500HD models equipped with the 6.6L Duramax diesel engine (RPO L5D). The coolant leak may be caused by a cracked heater outlet pipe along the lower bracket weld. (Fig. 25) Check for a coolant leak at the heater outlet pipe.


Fig. 25


If the coolant leak is coming from the heater outlet pipe, a new, redesigned pipe is now available. Replace the pipe, bracket and clamp. (Fig. 26) Be sure to torque all fasteners to specification. After filling the cooling system, check for any leaks before completing the repairs.


Fig. 26


If coolant is not leaking from the heater outlet pipe, refer to engine cooling diagnostics in the appropriate Service Information.

Refer to Bulletin #21-NA-143 for more details and parts information.


– Thanks to Bob Briedis

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