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John Deere 6068 diesel - Cylinder head inspect and reassembly operations
Remove cylinder head
Remove rocker arm cover, if not previously done. Drain all engine oil
and coolant. Disconnect turbocharger oil inlet line at turbocharger or
oil conditioning housing. Remove water manifold (A) and all coolant
piping. Remove turbocharger (B) and exhaust elbow (E). Remove air intake
manifold (C). Remove exhaust manifold.
A—Water Manifold, B—Turbocharger, C—Intake Manifold, D—Aftercooler
Assembly, E—Exhaust Elbow
Remove fuel injection lines (A) and nozzles (B). Remove rocker arm cover
(C) and ventilator outlet hose assembly.
Remove six cap screws (A) and remove all four clamps (B). Lift rocker
arm assembly up and remove. Remove wear caps from valve stems. Remove
all 12 push rods and identify for reassembly.
Clean and inspect push rods as explained later in this group. Remove all
26 cylinder head cap screws. If cylinder head gasket failed, check and
record each cylinder head cap screw torque before removing. Make a
reference mark (in-line) on socket and cylinder head surface. Loosen cap
screw at least 1/2 turn. Retighten cap screw (using torque wrench) until
reference marks align, and record torque.
Remove cylinder head gasket. Inspect possible oil, coolant, or
combustion chamber leaks. Also, check for evidence of incorrect or
defective head gasket being used. Do not rotate crankshaft with cylinder
head removed unless all cylinder liners are secured with cap screws and
large flat washers as described later in this group.
Disassemble and inspect rocker arm shaft assembly
Make preliminary inspection during disassembly. Look for: Worn or scored
rocker arms, shaft, and shaft support. Weak or broken springs. Lube oil
restriction. Remove plugs and washers from ends of rocker arm shaft.
Slide springs, rocker arms, and rocker arm supports off rocker arm shaft
identifying their parts for reassembly in the same sequence they were in
before disassembly. Inspect rocker arm shaft (A) for severe scratching,
scoring, or excessive wear at points of rocker arm contact. Measure
rocker arm and shaft. Compare with specifications given below.
Wear could indicate weak valve springs, bent push rods, or loose rocker
arm shaft clamps.
ROCKER ARM ASSEMBLY SPECIFICATIONS
Rocker Arm I.D - 19.07—19.10 mm (0.7507—0.7520 in.)
Rocker Arm Shaft O.D - 19.01—19.05 mm (0.7484—0.7500 in.)
Check rocker arm adjusting nut (C) and screw (B) for damage. Visually
inspect rocker arm for hairline cracks. Replace if necessary. Be sure
all oil holes in rocker arm shaft are clean and open. Clean all rocker
arm parts with clean solvent. Dry with compressed air. Check for cups or
concave wear on ends of rocker arms where they contact wear caps.
Examine spacer springs on shaft between rocker arms. Be sure they are
strong enough to exert a positive pressure on rocker arms. If the rocker
arm has been damaged by a valve failure, replace it and the push rods
when replacing valves. Roll rocker arm shaft and push rods on a flat
surface to check for bends or distortion. Replace parts as necessary.
Assemble and inspect rocker arm shaft assembly - Assemble parts on
rocker arm shaft opposite removal procedure. Make sure rocker arm shaft
end plugs are firmly seated against end of shaft, and washers are
installed on shaft.
Inspect and clean cylinder head
Inspect all John Deere 6068 diesel cylinder head passages for
restrictions. Heads with restricted or clogged passages can be cleaned
by soaking them in a tank of hot caustic solution. Scrape all old gasket
material from head. Use a powered wire brush to clean sealing surfaces.
If cylinder head is not put in a chemical hot tank for cleaning, clean
with solvent and a brush. Dry with compressed air and be sure to blow
out all passages.
Check cylinder head combustion face flatness - Check cylinder head
flatness using D05012ST Precision Straightedge and feeler gauge. Check
lengthwise, crosswise, and diagonally in several places. If any
measurement exceeds this specification, the cylinder head must be either
resurfaced or replaced.
CYLINDER HEAD TOP DECK FLATNESS SPECIFICATION
Maximum Out-of-Flat (Over Entire Length or Width) - 0.102 mm (0.0040
in.)
Straightness per any 305 mm (12 in.) Length - 0.025 mm (0.001 in.)
Measure cylinder head Thickness - Measure head thickness from valve
cover gasket rail-to-combustion face. If cylinder head thickness is less
than wear limit. Do not attempt to resurface. Install a new cylinder
head. If necessary to resurface cylinder head, a maximum of 0.762 mm
(0.030 in.) can be ground from new part dimension. Remove only what is
necessary to restore flatness. After resurfacing, check flatness as
described earlier and check surface finish on combustion face of head.
Check valve recess after grinding. Valve seat or valve face may be
ground to bring this characteristic within specification.
CYLINDER HEAD SPECIFICATIONS
Thickness - 155.45—155.71 mm (6.120—6.130 in.)
Wear Limit - 154.69 mm (6.09 in.)
Combustion Face Surface Finish (AA) - 0.015—0.0028 mm (60—110 micro-in.)
Maximum Wave Depth - 0.008 mm (0.0003 in.)
Install cylinder head
Thoroughly inspect new cylinder head gasket for possible manufacturing
imperfections. Return any gasket that does not pass inspection. Be sure
cylinder head and block gasket surfaces are clean, dry, and free of any
oil. Put a new head gasket on JD 6068 diesel cylinder block. Do not use
sealant on gasket; install dry. If cylinder head is lowered onto
cylinder block and you discover that the head is not positioned
correctly on locating dowels, remove cylinder head and install a new
gasket. Do not try to reposition cylinder head on the same gasket again
since the fire ring will possibly be damaged. Lower cylinder head everly
to correct position on block using appropriate lifting equipment. Make
sure that head is positioned correctly over dowels.
Install rocker arm assembly - Install push rods (A) in holes from which
removed. Install wear caps (B) on valves, making certain caps rotate
freely. Make sure spring pin (A) engages with hole (B) in shaft. Install
shaft clamps (B) and all six cap screws (A). Tighten cap screws to 75 Nm
(55 lb-ft).
Complete final assembly of injection pump side - Adjust valve clearance
as directed earlier in this group. Apply Adhesive or equivalent to new
gasket, and seal gasket to rocker arm cover (B). Be sure to follow the
manufacturer’s directions on the package for correct application
procedures and curing times. Install cover and tighten cap screws to 8
Nm (6 lb-ft) (72 lb-in.). Install fuel injection nozzles (E), leak-off
lines (D) and fuel injection lines (C). Connect ventilator outlet hose
to adapter on rocker arm cover and tighten clamp securely. Install water
manifold.
A—Water Manifold, B—Rocker Arm Cover, C—Fuel Injection Lines, D—Leak-off
Lines, E—Fuel Injection Nozzles
Complete final assembly on exhaust manifold side - Install front exhaust
manifold using new gaskets. Do not tighten cap screws until sealing ring
and rear exhaust manifold is installed. Install rear exhaust manifold
using new gaskets and sealing ring. Tighten cap screws in sequence shown
in bottom illustration to 47 Nm (35 lb-ft). Install turbocharger oil
return pipe, using a new O-ring.
On some John Deere Engines, using new gaskets install intake manifold
(A). Tighten cap screws to 47 Nm (35 lb ft). On some Engines, install
intake coupling (B). Do not tighten clamps. On some Engines, install
turbocharger (C), adapter (D), and exhaust elbow (E). Position intake
adapter with turbocharger and intake manifold and tighten clamps
securely.
A—Intake Manifold, B—Intake Coupling, C—Turbocharger, D—Turbocharger
Adapter, E—Exhaust Elbow
On JD diesel, use new gaskets (A) and install intake manifold (B).
Tighten cap screws to 47 Nm (35 lb-ft).
On JD Engines, using new gaskets and O-rings, install aftercooler and
cover - Install water inlet (A) and water outlet (C) hoses. Tighten hose
clamps securely. Install aneroid line (B), if equipped, and tighten
securely. Install turbocharger (D) with couplings. Tighten cap screws to
47 Nm (35 lb-ft). If engine oil was drained from crankcase, install new
oil filter and fill with clean oil of correct grade and viscosity. Fill
cooling system with clean coolant. Perform engine break-in.
A—Water Inlet Hose, B—Aneroid Line, C—Water Outlet Tube and Hose,
D—Turbocharger
Perform engine break-in - Run John Deere 6068 diesel engine at slow idle
no load for 2 minutes. Check for liquid leaks. Increase RPM to fast
idle, then load down to 50 rpm above rated speed for 20 minutes.
Dynamometer is the preferred load control, but engine can be loaded by
matching drag loads to gear selection. Recheck valve clearance and
adjust as necessary. Install rocker arm cover gasket and cover. Tighten
rocker arm cover cap screws to 8 Nm (6 lb-ft) (72 lb-in.). Retorque of
cylinder head cap screws after engine break-in is not required.
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