Turbocharger Volvo 760 I

DESCRIPTION

Volvo uses an exhaust driven turbocharger. The turbocharger is mounted on the right side of the engine. Components include the turbine, compressor wheel, rotor shaft, bearings, housing, and wastegate. In addition, a blow-off valve and a turbo warning light on the instrument panel are connected into the system.

OPERATION

The turbine wheel is driven by exhaust gases. As exhaust gas flow increases with engine speed, the turbine speed increases and compressor discharge increases. The turbocharger is designed to provide a relatively high discharge pressure at mid-range RPM.

Turbocharger lubrication is supplied by the engine oiling system. The shaft is supported by bearings using pressurized oil for lubrication. The shaft seals are a piston ring type. Oil supply and pressure must be sufficient to prevent shaft bearing failure.

The wastegate actuator monitors discharge pressure from compressor. When pressure reaches 10 psi (.70 kg/cm 2 ), actuator begins to open wastegate. As pressure increases, the regulator gradually increases wastegate opening.

Excessive compressor pressures may damage engine by inducing an overload, and are normally prevented by wastegate actuator. In case of failure of that system, a blow-off valve mounted on the end of the intake manifold is activated.

Scheme 17

PRELIMINARY CHECKS

1. Bring engine to normal operating temperature. Turn off engine. Turbine shaft will normally stop later than engine. If not, remove intake hose from compressor housing.
2. Verify compressor wheel rotates freely. Side and end play should be within specification. Ensure compressor wheel does not scrape against compressor housing when wheel is pushed radially or axially.

BOOST PRESSURE

1. Connect air pressure gauge in-line between fuel limiter and intake manifold hose. Use a "T" fitting and enough hose so gauge may be carried in passenger compartment.
2. Engine must be normal operating temperature. On manual transmission, drive in 3rd gear at approximately 1500 RPM. On automatic transmission, place selector in position "2".
3. Press accelerator pedal to floor. On automatic transmission, do not engage kickdown. Bring engine speed to 3000 RPM with accelerator depressed. Maximum boost pressure should be 6.5-8.0 psi (.46-.56 kg/cm 2 ).

BLOW-OFF VALVE

1. Unplug electrical connector from blow-off valve. Place jumper wire across connector terminals. Turn ignition on and check that warning lamp in instrument panel lights. If not, repair electrical circuit.
2. Plug in connector on blow-off valve. Using a pair of vise grip pliers, clamp hose between compressor housing and wastegate actuator. CAUTION: Engine must not be raced when pliers are installed on hose or damage may result.
3. On manual transmission, drive in 3rd gear. On automatic transmission, place selector in position "2". On both models, apply throttle carefully to approximately 3000 RPM while applying brakes.
4. Warning lamp should light and blow-off valve should open when pressure gauge indicates 11.4-12.1 psi (.80-.85 kg/cm 2 ). Do not exceed this boost pressure. Remove pliers immediately after test.

END & SIDE PLAY

Maximum end and side play is .020" (.5 mm). Replace turbocharger if worn beyond limits.

TROUBLE SHOOTING

Note. Replace turbocharger assembly if diagnosed as defective.

LOW BOOST PRESSURE

Check for clogged air filter. Inspect for leakage between compressor housing and cylinder head or between turbine housing and cylinder head. Inspect engine for low compression, incorrect valve clearance, or fuel deprivation. Check for wastegate valve stuck in open position. Check for clogged exhaust system or malfunction in turbocharger.

HIGH BOOST PRESSURE

Leakage from hose between compressor housing and wastegate actuator. Wastegate actuator diaphragm damaged. Wastegate valve stuck in closed position.

ENGINE KNOCK

Octane number of fuel too low. Incorrect injection timing. Boost pressure too high.

NOISE OR VIBRATION

Preheater plates loose or cracked. Leakage from intake or exhaust system. Poor turbocharger lubrication. Imbalance in turbocharger shaft, turbine or compressor wheel because of damage.

OIL LEAKS

Oil leakage on intake side from clogged air filter. Exhaust system loose or leaking. Excessive crankcase pressure. Oil return line blocked. Turbocharger shaft seals worn.

Removal

1. Remove negative battery cable, intake hose from turbocharger pipe, air cleaner, and preheater hose. Remove snap ring from turbocharger intake pipe. Remove compressor intake pipe and plug hole immediately.
2. Remove hose to blow-off valve. Remove oil return pipe mounts and move pipe aside. Plug pipe opening. Remove oil supply pipe. Disengage exhaust pipe from turbocharger.
3. Raise and support vehicle. Remove exhaust pipe-to-transmission support bracket. Remove turbocharger mounting nuts and lift off turbocharger.

Installation

To install, reverse removal procedure. Use new "O" ring on compressor-to-intake manifold pipe. Use new turbocharger-to-manifold mounting nuts. Tighten to 44 ft. lbs. (60 N.m).

Disassembly

1. Remove turbocharger as previously described. Remove air pressure and oil by-pass hoses from compressor housing. Mark position of compressor housing relative to turbine. Separate compressor housing from turbine. DO NOT damage compressor wheel.
2. Mark position of turbine relative to turbine housing. Separate turbine from housing. Do not damage turbine wheel. Remove wastegate chamber cover. Remove gasket.

Cleaning & Inspection

1. Clean and check all parts for cracks, damage, wear, smooth mating surfaces, or blockages in oil or air channels. Ensure wastegate valve contact surfaces are not burnt. If valve is burnt, turbine housing must be replaced.
2. Check turbine wheel and bearing for damage or wear. Check end and side play. If defective, turbine assembly is replaced as an assembly.
3. Connect an air supply and air pressure gauge to the thick hose on the wastegate actuator. Plug off the thin hose. Slowly increase pressure. At 10.8-12 psi (.76-.84 kg/cm 2 ) the valve should open .047-.051" (1.2-1.3 mm). If valve does not open as specified, replace wastegate actuator and housing.

Reassembly

1. Use new gaskets for reassembly. If installing new compressor housing, transfer nipple and plug. Coat threads with Sealing Compound (116 1035-9). Align identification marks made on disassembly and install turbine and compressor housing on turbine assembly.
2. Tighten turbine housing bolts to 15 ft. lbs. (20 N.m) and compressor housing bolts to 13 ft. lbs. (18 N.m). Install wastegate chamber cover with round bevel (raised portion) turned toward the valve. Use new lock washers and tighten nuts to 7 ft. lbs. (10 N.m). Install oil by-pass and pressure hoses.