K 20 3/4 Ton Pickup 4WD V8-379 6.2L DSL VIN C FI (1982)
Air Filter Element: All Technical Service Bulletins
Air Filter - Carbon Deposits
Number:
82-T-142
Section:
VI
Date:
APR., 1983
Subject:
CARBON DEPOSITS ON AIR FILTER - 1982 LIGHT DUTY TRUCKS WITH 6.2L DIESEL ENGINES (VIN CODES C & J)
TO:
ALL CHEVROLET DEALERS
Build up of soot (carbon) or contamination of the air filter element is a result of exhaust gases emitted from the EGR valve.
During normal operation of the EGR valve, some soot will occur in the intake manifold below the EGR valve. A soot deposit will also
occur on the inner surface of the air cleaner element and housing. This is normal. The air filter element air flow will not be affected, and
should last the specified change interval.
Should soot build-up be excessive, and/or evidence of filter deterioration occurring, the following may have occurred:
1.
Malfunction of the EGR system (evidenced by excessive black exhaust).
2.
Malfunction or setting of the TPS (throttle position switch). Refer to Service Manual.
3.
Mode of vehicle operation. If the vehicle is idled for long periods, or long downhill operation with closed throttle, the build-up may
be excessive.
To direct the EGR exhaust gas directly into the intake manifold, a baffle, P/N 25042774, has been released for service. The installation of
this baffle will prevent the sooting of the filter element. Malfunctions or improper settings of the EGR/TPS system will still cause excessive
black smoke and poor performance. Conditions in these areas should be corrected promptly.
BAFFLE INSTALLATION
To install this baffle, refer to the sketch below and the following steps:
1.
Remove air filter housing from engine. (Disconnect EGR hose at EGR valve and at solenoid.)
2.
Clean housing and cover.
3.
Inspect air cleaner gasket on manifold. If it is torn or missing, install a new gasket.
4.
Install air cleaner housing.
5.
Replace element if required.
6.
Install baffle and element. Assure proper seating of both. (Attach vacuum hose to EGR valve and solenoid.)
7.
Install cover and tighten wing nuts.
