School Bus Cummins ISB Head Gasket repair

Mechanics Hub - December 7, 2013
Cummins ISB Head Gasket

The Cummins 24 valve ISB in the video requires a new head gasket. This 2003 model year head gasket was leaking from the right front corner which is a common problem with these models. The head bolts have to be checked for stretch with a gauge that comes with the head gasket kit.

The head itself weighs 80 pounds so a hoist is handy to have around but it has to have a long reach. An A-frame would do wonders for this job. The conventional Freightliner would allow us to remove the hood but to save time it's not absolutely necessary.

Head and Block Inspection

After cleaning the block surface we check for cylinder scoring and cracks on the deck surface then check the block deck with a straight edge. There's a small window for wear within thousands of an inch checking under the straight edge with a feeler gauge.

ISB Injector Removal

Removing injectors is required before removing the head because the injector tips protrude... if you were to set the head down on a work bench the injectors would get damaged. They are secured with 2 bolt hold downs. Once they are removed the threaded holes on top of the injectors makes removal easy with a slide hammer. An o-ring seals the injector in the head. Fuel Supply To Injectors

The fuel connectors in the head connect the fuel lines to the injectors. They are sealed with an o-ring and have a tapered end that seats against the injector body. The injector can only be installed in the head one way because of the hold downs that index the injector in the right position to align perfectly with the fuel connectors. Head Bolt Torque Procedure

Starting from the middle of the head the typical circular pattern applies. Torque to 59 ft. Lbs first then 77 ft. Lbs. After rechecking the torques using the same pattern advance the head bolts another 90 degrees.

The Cummins ISB Stands Up Well

The Cummins ISB engines in our fleet have been extremely dependable. The only repairs that stand out has been the head gaskets and fuel transfer pumps. You can not beat that kind of performance!