Turbocharger: Service and Repair

The turbocharger is an exhaust driven device which compresses the air/fuel mixture that is used to increase engine power on a demand basis, allowing a smaller, more economical engine to be used.

A turbine in the exhaust gas flow is connected through a shaft to the impeller (compressor). During normal, steady operation, the turbine does not rotate with sufficient speed to boost pressure to compress the air/fuel mixture. As speed increases, the mixture is compressed, allowing the denser mixture to enter the combustion chambers and develop more engine power during the combustion cycle.

The intake manifold pressure (boost) is controlled by a wastegate valve which is used to bypass a portion of the exhaust gases around the turbine at a predetermined point in the cycle, limiting the boost pressure.

SERVICE

When servicing the turbocharger, observe the following precautions:
1. Thoroughly clean all connections and areas around the connections prior to disconnecting.
2. Place removed parts on clean surface and cover with paper or plastic.
3. Components that have been opened or disassembled must be covered or carefully sealed if repair cannot be carried out immediately.
4. Install only clean components. Unpack replacement parts immediately before installation and do not use parts that have been stored loose.
5. When fuel system is open, do not work with compressed air or move vehicle unless absolutely necessary.

Turbocharger, Replace

1. Remove air cleaner assembly.
2. Disconnect battery cables at battery and remove battery from vehicle.
3. Remove right side engine mount heat shield, engine cover plate, and alternator.
4. Disconnect exhaust pipe at turbocharger and remove exhaust bracket at transmission.
5. Disconnect oil supply line at turbocharger.
6. Loosen lower hose clamp of hose connection to intake manifold.
7. Remove oil return line and air tube.
8. Remove four attaching nuts between turbocharger and exhaust manifold, loosening two rear nuts from above.
9. Remove turbocharger.
10. Reverse procedure to install, noting the following:
a. Install turbocharger and tighten attaching nuts sufficiently so that air hose on intake manifold can be attached to turbocharger, then torque nuts to specifications.
b. Fill connection branch of turbocharger with engine oil and connect oil supply line.
c. After installing turbocharger, run engine approximately one minute at idle speed so oil supply of turbocharger is properly distributed.

Testing

1. When performing testing, note the following:
a. Ensure that there are no leaks at intake or exhaust gas side.
b. Measure boost pressure with engine at full throttle on road test or on a dynamometer.
c. Ensure that test time does not exceed ten seconds per measurement.
2. Using T-fitting, install suitable pressure gauge in hose between intake pipe and fuel injection pump, then position gauge so that it can be read from driver's seat.
3. Open gauge stop valve by pushing inward.
4. Measure boost pressure with engine at full throttle as follows:
a. On dynamometer, with manual transmission measure at 4000 RPM in 3rd gear, with automatic transmission measure at 4000 RPM in second range.
b. On road test, with manual transmission measure in 2nd gear while slowing vehicle to 37 mph with brake, with automatic transmission measure in 1st range while slowing vehicle to 37 mph with brake. To make boost pressure reading easier during road test, pull gauge stop valve outward to lock reading on gauge.
5. If boost pressure exceeds 9-10 psi, replace wastegate.
6. If boost pressure is less than 9-10 psi, proceed as follows:
a. Disconnect blow-off valve hose from intake air hose.
b. Plug air hose with one inch plug and secure plug with clamp.
c. Repeat step 4.
d. If boost pressure is within specifications, replace blow-off valve.
e. If boost pressure is less than specifications, replace wastegate temporarily.
f. Repeat step 4.
g. If boost pressure is not within specifications, replace turbocharger.