Vapors, formed within the engine, are removed from the crankcase, gear train and valve compartment by a continuous pressurized ventilating system.
A slight pressure is maintained in the engine crankcase by the normal seepage of a small amount of air and combustion gases past the piston rings. These gases are swept up through the engine and pass through a crankcase breather. The gases are then vented to the atmosphere.
Breather extension hoses may be required on certain Series 50 engines used in on-highway vehicle applications.
Under certain conditions, the vapors from an operating engine may be circulated through the battery charging alternator by the alternator cooling fan. Excessive ingestion of vapors may lead to alternator malfunction. This can occur if the internal components of the alternator become coated with oil-laden dust or road grit.
To minimize the potential for this condition, check the length of the engine breather tube and add an extension hose, if necessary. For proper dissipation of vapors, the end of the breather hose must extend at least twelve inches below the oil pan rail.
Note: The S50G automotive engine uses a closed crankcase breather system. Refer to Section for more information.
A wire mesh element is located inside the valve cover, or in a separate housing on the valve cover cap or at the gear case cover. This element traps excess engine oil particles in the vapor and returns them to the crankcase. See Figure 24371 .
1. Wire Mesh Element
5. Valve Cover Cap
7. Breather Housing
Wire Mesh Elements
A new baffle (23515095) has been added to the breather assembly on the two-piece, low profile aluminum valve rocker cover used on Series 50 engines. This change went into production on June 29, 1993, effective with unit serial number 04R001729. The change was also made to unit 04R001001 (built June 5, 1993) on a single engine pre-production basis.
The new baffle redirects oil splash from the rocker arms, preventing oil from contaminating the breather element. See Figure 24272 . Oil trapped in the breather medium can drip out of the breather tube and may cause faulty high crankcase pressure readings.
1. Retainer Clip
5. Breather Housing
2. Wire Mesh Element
3. Rocker Cover
8. Valve Cover Cap
Breather Component Location
To determine if repair is possible or replacement is necessary, perform the following procedure. See Figure 21758 .
Flowchart for Repair or Replacement of Ventilating System
Precleaning is not necessary.
Remove ventilating system as follows:
Breather-Oil Fill Tightening Sequence
1. Breather Housing
4. Retainer Bolts
2. Wire Mesh Element
5. Housing Bolts
Breather-Oil Fill Housing
Clean the wire mesh element components prior to inspection as follows:
To avoid injury from flying debris when using compressed air, wear adequate eye protection (face shield or safety goggles) and do not exceed 40 psi (276 kPa) air pressure.
Inspect the ventilating system as follows:
Install the ventilating system as follows:
Note: Do not leave gaps around the edges.
Note: The baffle must be installed with bolting flanges against the retainer to permit proper engine breathing.