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 Section 4B.
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.
To install this baffle, refer to Figure 3-9 below and use 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.
