TROUBLESHOOTING
Page 105
It is normal for some air bubbles to form in the
cooling system as a result of the engine warming
up to operating temperature.
7. Apply a soap-and-water solution between
two cylinder heads to check for external
combustion leakage.
Cylinder Head Fuel Passages Leak
Check — In Chassis
The symptoms of coolant-in-fuel are a loss of
coolant with no apparent external leak, together
with one or more of the following: coolant in fuel
tank, coolant in fuel filter or yellow fuel out of fuel
return line.
1. Remove the nozzles from both cylinder
heads and pressurize the cooling system
with a maximum of 15 psi (103 kPa) air
pressure and look for coolant coming out
around the nozzle sleeves.
2. Look into each nozzle sleeve bore for signs
of coolant leakage.
3. A cracked or leaking nozzle sleeve should
be replaced as an on-engine repair using the
procedures described under “ENGINE
DISASSEMBLY” procedures in the REPAIR
INSTRUCTIONS section. If after replacing
the nozzle sleeve(s) the re-pressure test
shows that the problem still exists, the
cylinder head(s) should be replaced.
Cylinder Block/Cylinder Head
Coolant Passages Leak Check — In
Chassis
Refer to Figure 99.
1. Drain coolant from the engine.
2. Remove the engine oil pan and cylinder
head valve covers.
3. Remove the water pump assembly and use
a suitable plate and gasket to seal the
opening.
4. Remove the upper and lower hoses from the
thermostat housing. Remove the thermostat
housing and thermostat(s).
5. Secure a suitable plate and gasket over the
thermostat housing opening in the coolant
manifold.
6. Install an air fitting into one of the pipe plug
holes in the coolant manifold.
7. Reinforce the hose connecting the coolant
manifold sections by installing a hose clamp
around the center of the hose to prevent the
hose from rupturing during testing.
8. Remove one of the large pipe plugs from the
water manifold and add hot water to fill the
cooling system. Increase cylinder block
temperature to 150°F (66°C). Loosen one of
the pipe plugs near the top of the cylinder
block to bleed air from the water jacket while
filling. Also open the block drain to allow
water to flow out. This will help warm the
cylinder block. Tighten the loosened pipe
plug after all of the trapped air has escaped.
9. After the cylinder block is sufficiently heated,
close the block drain and apply
approximately 50 psi (345 kPa) air pressure
to the air connection.
Do not exceed 50 psi (345 kPa) air pressure.
Damage to seals or cup plugs may result.
10. Check for coolant leaks at the bottom of
each cylinder bore.
앫 Coolant leaking between the cylinder
sleeve outside diameter and cylinder
block indicates a leaking cylinder
sleeve seat.
앫 Coolant leaking down the inside
diameter of the cylinder sleeve
indicates a leaking head gasket.
Water leaking from the No. 2 or No. 5 cam
bushings or from the No. 2 or No. 5 main
bearings can indicate a breakthrough between
the rocker arm feed passage and the water jacket
(cylinder head).
5-111.bk Page 105 Monday, July 10, 2006 2:26 PM
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