Head gasket failures don’t happen often, but when they do, they require action.  Replacement of a head gasket on a Cummins Turbo Diesel engine is relatively straightforward, and not unlike the same job on any other diesel or gasoline engine.  The main difference is the size of the cylinder head on the Cummins – it’s big and heavy, and will require the use of an engine hoist or other lifting device to remove from the vehicle.

A head gasket, as the name implies, is the seal between the cylinder head, which sits atop the engine, and the engine block itself.  The main purpose of this seal is to keep the engine coolant, which needs to circulate through both the block and head, inside the special passages, called water jackets, that allow it to pass from one to the other.  When the gasket fails, coolant will leak either to the outside of the engine, or into the cylinders themselves, where it will boil off and some out the tailpipe as steam.

A brave DIY mechanic, with some experience and the right tools, can usually handle the job.  Warning – this is not a morning’s work.  The uninitiated can expect to spend more than a day under the hood of the truck.


There are a number of attachments to the engine that will have to be removed, including the turbocharger, the exhaust manifolds, and the intake manifold.  There is a proper sequence for removal of the head nuts from their studs.  All nuts bolts should be labeled and kept organized for reinstallation.  Now is a good time to replace the studs with higher quality aftermarket ones. ARP studs from American Racing Products are standard.

Lifting the head off the engine block will require an engine hoist, and often some good persuasion, as the existing gasket might hold them together.

Replacing the Gasket

The mating surface between the head and the block needs to be thoroughly cleaned, with care taken not to get debris into the cylinders.  A vacuum can be used to remove anything that falls in.

Reinstalling the Head

Replacement is the reverse of removal.  Once the head is torqued down (be very aware of the specific order and torque specifications) the valve lash must be set – relatively complex procedure that involves rotating the engine by hand, and checking the clearance on the rocker arms from the valve stems before tightening them.

If you need your head gasket replaced or any other work done to your diesel vehicle, visit IamDIESEL Diesel Service Centre, the service branch of Western Turbo, Winnipeg’s premier diesel centre.