MBE4000 APPLICATION AND INSTALLATION
7.15
COOLING SYSTEM DIAGNOSTICS AND
TROUBLESHOOTING GUIDE
System diagnostics and troubleshooting covers:
□
Engine overheat
□
Cold running engine
□
Poor cab heater performance
7.15.1
ENGINE OVERHEAT
Coolant temperatures should not exceed maximum limit of 105°C (221°F) so metal and oil
temperatures can be controlled for optimum engine performance, fuel economy, and life.
Obvious overheat conditions are determined from the coolant temperature gauge, warning, or
shutdown devices. Steam vapor or coolant being expelled through the pressure relief over
fl
ow
tube is another indication of overheat. Reduced engine performance or engine oil having a burnt
odor are other indicators.
Troubleshooting for Engine Overheat
Troubleshoot for engine overheat as follows:
1. Check for inaccurate gauge, warning, or shutdown device, insuf
fi
cient coolant
fl
ow, and
inadequate heat transfer capabilities during coolant side investigation.
HOT COOLANT
To avoid scalding from the expulsion of hot coolant, never
remove the cooling system pressure cap while the engine is
at operating temperature. Wear adequate protective clothing
(face shield, rubber gloves, apron, and boots). Remove the
cap slowly to relieve pressure.
2. Check that the various temperature monitoring devices are calibrated.
[a] Sensor probes
must
be located (before thermostat) in a high temperature, well mixed
coolant
fl
ow path.
[b] The sensor
must
be free of scale and other contamination.
3. Check for insuf
fi
cient coolant
fl
ow. The following may be causes of insuf
fi
cient coolant
fl
ow:
□
Thermostat -- Stuck, sluggish, worn, broken
All information subject to change without notice.
(Rev. 03/06)
7-53
7SA250 0603
Copyright © 2006 DETROIT DIESEL CORPORATION