Cummins N14 STC, Celect, Celect Plus – Service Manual 012-103   Air Compressor Cylinder Head (Holset® SS and E-Type Models)

WARNING  The unloader valve body is installed with spring tension. Use care when removing to prevent personal injury. Always wear protective eye wear.

Hold the unloader valve body down and remove the two captive washer capscrews and the two plain washers.

Remove the unloader valve body.

Remove the o-ring seal.

Remove the rectangular ring seal.

Remove the unloader valve cap and the unloader valve spring.

Remove the intake valve seat and valve.

Remove the intake valve spring.

Remove the capscrews, lock washers, and plain washers that hold the cover and head to the crankcase.

Remove the cover and discard the gasket.

Remove the head and discard the gasket.

Hold the head bottom side up, and use thumb pressure to remove the exhaust valve seat assembly.

NOTE: If the exhaust valve seat assembly can

not be removed by thumb pressure, use valve seat puller, Part Number 3822674. A press and air compressor seat removal tool, Part Number 3377416, can be used to remove the exhaust valve seat.

Remove the o-ring seal from the exhaust valve seat or head. Remove the exhaust valve.

Remove the compression spring and wear plate from the head.

WARNING  When using solvents, acids, or alkaline materials for cleaning, follow the manufacturer’s recommendations for use. Wear goggles and protective clothing.

Soak the parts in a kerosene emulsion-based cleaner designed to remove carbon. The cleaner

must have a pH of 9.5 or less to avoid turning aluminum parts black. The cleaner manufacturer or supplier

must be contacted about solution concentration, temperature, and soak time.

NOTE: Do

not use a scraper to remove carbon and scale, the sealing surfaces can be damaged.

The parts can be scrubbed with a stiff nonmetallic bristle brush.

Inspect the intake and the exhaust valves for cracks or other damage.

Measure the flatness of the intake and exhaust valves. Both valves must be flat within 0.03 mm [0.001 in].

NOTE: Holset Engineering Co., Inc. recommends that new valves be installed.

Apply a bluing compound to the exhaust valve seating surface.

Install the exhaust valve on the valve seating surface and check the seating area. Replace the seat if the contact area is

not 100 percent.

Measure the exhaust valve seat height.

If the seat height is less than 12.32 mm [0.485 in], replace the seat.

Apply a bluing compound to the intake valve seating surfaces.

Install the intake valve on the valve seating surface and check the seating area. Replace the seat if the contact area is

not 100 percent.

Measure the intake valve seat height.

If the seat height is less than 6.86 mm [0.270 in], replace the seat.

Use valve spring tester, Part Number 3375182, to check the intake, exhaust, and unloader valve springs. Replace any springs that do not meet specifications.

NOTE: Holset Engineering Co., Inc. recommends that new springs be installed.

Reference the Compressor Spring Force Specifications chart shown below.

Install the wear plate and compression spring in the head as shown.

Install the exhaust valve on the exhaust valve seat.

Install the o-ring seal on the seat.

Use clean 15W-40 oil to lubricate the o-ring seals.

Use hand pressure to install the exhaust valve assembly in the head.

NOTE: For SS-296 and ST-676 air compressor models, a press and air compressor seat installation tool, Part Number 3377415, can be used. Exhaust valve seat puller, Part Number 3822674, can also be used to install the valve seat.

Use new gaskets to install the cylinder head and cover.

Install the flat washers, lock washers, and capscrews.

Tighten the cylinder head capscrews of the single cylinder compressor in an alternating sequence.

Install the intake valve spring with the tang down.

Install the intake valve.

Install the intake valve seat with the flange side up.

Install the unloader valve cap spring.

Install the unloader valve cap.

Use high temperature grease (Accrolube Lubrication Teflon™ Grease or equivalent) to lubricate the outside diameter of the cap.

Install the new rectangular ring seal into the unloader body.

NOTE: The seal

must be installed with the grooved side up.

Install a new o-ring seal on the unloading valve body.

Use clean 15W-40 oil to lubricate the seal.

Install the compression spring.

Use Accrolube Lubrication Teflon™ Grease to lubricate the outside diameter of the unloader cap and install it into the unloading valve body.

Install the unloading valve body.

CAUTION  Do not over-tighten these screws. Compressor damage will result.

Hold the unloader body down and install the two plain washers and captive washer capscrews.

Tighten the capscrews.