Engine runs too hot:
If coolant temperature is too high, pressure will be
high enough to move the cap off of the sealing
surface in the radiator and cause coolant loss
through the overflow tube. See Problem No. 26,
Above Normal Coolant Temperature.
Expansion tank too small:
The expansion tank can be either a part of the
radiator or it can be installed separately from the
radiator. The expansion tank must be large enough
to hold the expansion of the coolant as it gets warm
or has sudden changes in pressure. Make sure the
expansion tank is installed correctly, and the size is
according to the recommendations of the OEM.
Cylinder head gasket leakage, or crack(s) in cylinder
head or cylinder block:
Remove the radiator cap and with the engine
running look for air bubbles in the coolant. Bubbles
in the coolant are a sign of probable leakage at the
head gasket. Remove the cylinder head from the
engine. Check the cylinder head, cylinder walls
and head gasket surface of the cylinder block for
cracks. When installing the head, use a new head
gasket. Tighten the bolts that hold the cylinder
head according to the Specifications Section of the
C. Internal Leakage
Erosion or crack(s) in injector sleeves:
If fuel is detected in the coolant, a possible cause is
a defective injector sleeve. Remove the injectors
and inspect the sleeves for cavitation erosion or
cracks. Replace any defective sleeves.
Cylinder head gasket leakage:
If the cylinder head gasket leaks between a water
passage and an opening into the crankcase,
coolant will get into the crankcase.
Crack(s) in cylinder head:
Crack(s) in the upper surface of the cylinder head,
or an area between a water passage and an
opening into the crankcase, can allow coolant to get
into the crankcase.
Crack(s) in cylinder block:
Crack(s) in the cylinder block between a water
passage and the crankcase will let coolant get into
Problem 37: Air Inlet Heater (If Equipped)
Heater Stays On Longer Than Allotted Time - Any Cycle
Heater Does Not Come On
Crank Heat Cycle
Regular Heat/Run Cycle
Heater Element Check
Coolant Sensor Check
Oil Pressure Switch Check
Heater stays on longer than allotted time-any cycle:
Replace the air inlet heater control module (if
Cycle times are approximate only. Some variance
does not necessarily indicate a system failure.
Heater does not come on:
Check for the following:
a detective heater control module.
a detective oil pressure switch (regular heat cycle only).
a defective coolant sensor.
a defective heater element.
a detective power relay (magnetic switch).
To avoid personal injury (burns, make sure the coolant
temperature is below 37.8°C (100°F) before performing any
Air Inlet Heater (AIH) controls and wiring may be
different for various engine applications. Refer to
electrical information and Parts book for the
Problem 38: Soot In The Inlet Manifold
On diesel engines a small amount of soot is normal.
This is due to the design characteristics of the engine.
Valve overlap allows the intake to open slightly before
the exhaust stroke has been completed, which will allow
some soot to be pushed into the inlet manifold.