Leaking Cylinder Head Gasket
Pre-chambers must not be recessed into the cylinder head or protrude out of the cylinder head by more than .004″ or a head gasket leak may result.
This measurement should be made at two or more points on the pre-chamber where the pre-chamber seats on the head gasket heat shield and sealing ring. Using a straight edge and a thickness gage or dial indicator, measure the difference between the flat of the pre-chamber and the flat surface of the cylinder head. A slight variance from one side of the pre-chamber to the other provided both sides are within the tolerance will result in a good seal.
External engine coolant loss on the 6.2L Diesel has generally been from the rear lower corner on the left hand cylinder head and the front lower corner on the right hand cylinder head. This coolant loss condition is the result of inadequate sealing around the core cleanout hole in the cylinder head. (Figure 2-15)
A contour shaped brass plug, P/N 14079353, has been developed to seal this core hole. In 1983 mid-year, the core cleanout hole will be machined and a plug installed in production. 1985 and later units will have this hole eliminated.
To reduce cylinder head gasket coolant leakage conditions, the following procedure should be adhered to whenever a cylinder head is removed for service:
TORQUE AND ANGLE TURN CONTROL TORQUING PROCEDURE FOR CYLINDER BOLTS.
This new torquing procedure is to be used on all 6.2L Diesel engines. It is to correct external and internal leak conditions.
1. After the removal of the cylinder head and gasket, all cylinder head bolts and bolts holes must be cleaned of all sealer (e.g. wire brush).
2. Check head and block for warpage overall .006 in. (.15mm) or .003 in. (,075mm) within 6 inches and .003″ transversely.
3. Wipe all surfaces clean.
4. Install new head gasket, either use: Victor (green) 14066260 (internal combustion leaks) or, Fel-Pro (red) 14066246 (external coolant leaks). Install the gasket over the dowel pins. The pre-chamber shields must be up.
5. INSTALLATION OF BRASS PLUG IN CYLINDER HEAD COOLANT CORE HOLE. (See Figure 2-15).
a. Check if a plug has been previously installed. If a plug is present, visually check condition. If plug appears questionable, remove and replace.
b. Check cored hole for excessive roughness or casting irregularities. Use a file to remove burrs and break sharp edges. Clean with a wire brush and wash with solvent.
c. Coat the sides of brass plug and the hole with Loctite 620; or 271, (GM #1052624 kit).
Using an Arbor Press or vice, slowly press brass plug into the hole using a flat steel plate or the plastic installation tool from kit #14077197 to squarely load the plug. Press in until plug is flush with head surface. Do not use a hammer as plug may be damaged. Allow Loctite to set 30 minites.
6. REPLACE ALL HEAD BOLTS WITH PART #14077193.
7. Due to clearance on C-K vehicles, the left rear cylinder head bolt must be installed into the head prior to installation. (Refer to Step 9 for sealing of bolt).
8. Carefully guide the cylinder head into place.
9. Coat the thread and bottom of the bolt head of the cylinder head bolts with sealing compound 1052080 or equivalent, and install bolts finger tight.
10. In sequence, torque all bolts to 25 N.m. (20 ft. lb.). (Figure 2-16).
11. In sequence, re-torque all bolts to 65 N.m. (50 ft. lb.). (Figure 2-16).
12. In sequence, turn each bolt an additional 90 degrees (V\ turn). This is to assure a more uniform bolt tension. (Figure 2-16).