Hummer H3. Manual — part 469

The PCV orificed tube (5) restricts the flow rate of the blow-by gases using a 2.5 mm (0.098 in)
orifice located in the camshaft cover tube (5). If abnormal operating conditions arise, the system
is designed to allow excessive amounts of blow-by gases to back flow through the crankcase
ventilation fresh air tube (6) into the air cleaner resonator (1) in order to be consumed by normal
combustion.

DRIVE BELT SYSTEM DESCRIPTION

The drive belt system consists of the following components:

The drive belt

The drive belt tensioner

The drive belt idler pulley

The crankshaft balancer pulley

The accessory drive component mounting brackets

The accessory drive components

The power steering pump, if belt driven

The generator

The A/C compressor, if equipped

The engine cooling fan, if belt driven

The water pump, if belt driven

The vacuum pump, if equipped

The air compressor, if equipped

The drive belt system may use 1 belt or 2 belts. The drive belt is thin so that it can bend
backwards and has several ribs to match the grooves in the pulleys. The drive belts are made of
different types of rubbers, chloroprene or EPDM and have different layers or plys containing
either fiber cloth or cords for reinforcement.

Both sides of the drive belt may be used to drive the different accessory drive components. When
the back side of the drive belt is used to drive a pulley, the pulley is smooth.

The drive belt is pulled by the crankshaft balancer pulley across the accessory drive component
pulleys. The spring loaded drive belt tensioner keeps constant tension on the drive belt to prevent
the drive belt from slipping. The drive belt tensioner arm will move when loads are applied to the
drive belt by the accessory drive components and the crankshaft.

The drive belt system may have an idler pulley, which is used to add wrap to the adjacent pulleys.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

Some systems use an idler pulley in place of an accessory drive component when the vehicle is
not equipped with the accessory.

ENGINE COMPONENT DESCRIPTION

Engine Block

The lost foam all aluminum engine block utilizes a deep skirt design for increased rigidity. The
cylinders are positioned in a straight in-line orientation. The crankshaft bearing caps have a
bearing beam or "ladder" for enhanced structural rigidity and vibration reduction.

Oil Pan

A single piece cast aluminum oil pan contributes to crankshaft and block rigidity while reducing
overall weight. The oil pan bolts to the bell housing as well as the block. This eliminates points of
vibration and makes the complete powertrain act as a single casting. Jack screws are used to
remove the oil pan.

Crankshaft

The crankshaft is a nodular iron design.

Connecting Rods

The connecting rods are forged powdered metal. The connecting rods and caps are of a fractured
split design to improve durability and reduce internal friction. Care must be taken to ensure the
mating surfaces are not damaged during service procedures.

Pistons

The pistons are a full-floating design. The piston pins are a slip fit in the bronze bushed
connecting rod and are retained in the piston by round wire retainers. There are 2 compression
rings and 1 oil control ring.

Cylinder Head

The cylinder head is also made of the lost foam aluminum for lighter weight and rapid heat
dissipation. There are 4 valves per cylinder and the ports are of a high swirl design for improved
combustion. The cylinder head gasket consists of a steel laminated construction.

Valve Train

The engine utilizes dual overhead camshafts and roller followers for reduced friction, which
results in improved gas mileage.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

Fuel System

A new electronic throttle control system is used on the engine. A throttle actuator control or TAC
system eliminates cable linkage from the pedal to the throttle control module. All throttle
movements are controlled by the powertrain control module (PCM).

Oil Pump

The oil pump is gear driven directly from the crankshaft. The oil pump drive gear is a slip fit to
the crankshaft.

Engine Covers

There is a front engine cover and a rear engine cover, both are made of aluminum. The front
engine cover and rear engine cover have "T" sealing joints and need to be removed after the oil
pan. The front and rear covers need to be installed before the oil pan. Jack screws are used to
remove the covers. Guide pins are used to aid in the installation of both covers.

EXHAUST CAMSHAFT POSITION ACTUATOR DESCRIPTION

The camshaft position actuator is bolted to the front of the exhaust camshaft and is integral with
the sprocket. The actuator and sprocket can only be replaced as one unit. The total range of
actuator rotation is 0 to 25 camshaft degrees. At idle, the exhaust camshaft position actuator is at
full advance or 0 degrees.

NEW PRODUCT INFORMATION

The purpose of New Product Information is to highlight or indicate important new features for
the service community.

Changes may include one or more of the following items:

Torque values and/or fastener tightening strategies

Engine specifications

New sealants and/or adhesives

Disassembly and assembly procedure revisions

Engine mechanical diagnostic procedure revisions

Special tools required

New Sealants and/or Adhesives

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

U.S. and Canadian SPO part numbers

3-Bond sealant P/N 12378521

Engine Features

Powder metal connecting rods with oil squirter hole

Full floating piston pins

Lost foam casted aluminum block and head

Aluminum camshaft cover

Electronic Throttle Control - ETC

Composite intake manifold

Bridge/bearing beam - stiffener ladder

Stainless steel fuel rail

Coil-on-plug ignition system

Inlet side thermostat

No EGR

LUBRICATION DESCRIPTION

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3