a hose doing its job, replacement should be made. Clamps
should be inspected to ensure they are strong enough to hold
a tight connection.
TRANSMISSION OIL COOLER
On some trucks equipped with automatic or semi-automatic
transmissions, the transmission oil is circulated through an oil
cooler or heat exchanger. The function of this unit is to control
transmission temperature and thereby keep oil in the proper
temperature range for its most efficient lubrication. This is
accomplished by using engine heat to bring transmission
temperature up or by using the cooling system to dissipate any
excessive heat generated within the transmission. Leakage
contamination between the cooling system and transmission.
FAN AND ACCESSORY
Fan and Accessory Drive Belts
New belts have a break-in period and lose tension during
NOTE - New belt Initial Installation tension Is higher than
the re-tension value applied to a used belt (run five
minutes or longer). This Is done to minimize number of
belt adjustments and prevent belt operation under low
tension during break-in period.
Belt tension checks must be performed using a Belt Tension
Gauge, such as a Howard KRIKIT Gauge, tool number 7401-
0071. This tool is available from:
Howard Manufacturing Company
59996 South Crocker
Little Town, Colorado 80120
Phone (303) 794-2510
NOTE - Use of the KRIKIT Gauge Is restricted to SAE 3/8,
1/2 and 11/16 Inch belts. Check tension on the midpoint
range of the longest span of belt.
New belts should be checked at 483 km (300 miles) or 10
hours, then checked again after 2 414 km (1, 500 miles) or 50
hours. The second service adjustment of belts establishes
Before adjusting belt tension, check the tension several times.
Use an average of the readings.
Belt tension checks must be made at midpoint between
pulleys at the longest belt span. Refer to Belt Tension Chart.
The 9.0 liter fan and water pump drive belts have an idler
pulley with spring tension. No adjustment is needed.
In multi-belt drives, the belt tension readings taken on the
same span may vary considerably between belts. When this
occurs, average readings to establish applied tension, except
in the application of the DT/DTI 466
engines power steering pump (Vickers), where the values
stated are for each belt.
Belt Tension Chart
New Belt Installation
New Truck upon delivery
After 10 hours (or 300 miles)
After 50 hours (or 1, 500 miles)
At intervals of 200 hours
(or 6, 000 miles)
Minimum Permissible Tension
*DT/DTI 466 Engine Power Steering (Vickers) Pump
New Belt - 356 Nm (80 lb-ft) per belt
Re-tension - 222 Nm (50 Ib-ft) per belt
Minimum Permissible Tension - 222 Nm (50 Ib-ft) per belt
EFFECTS OF COOLING SYSTEM
A neglected cooling system can lead to inefficient engine
operation, either directly or indirectly. Most of the problems
may be traced to overheating; however, an engine that is
running too cold can be just as troublesome.
Overheating may lead to troubles such as the following:
Pinging or knocking.
Poor lubrication-increased engine wear.
Sticking valves and valve lifters.
Short spark plug life.
Engine hot spots.
Need for higher octane fuel.
Overcooling often results in the following:
Excessive fuel consumption.
Sludge formation in crankcase.
Corrosive acids found in crankcase.
COOLING SYSTEM MAINTENANCE
COOLING SYSTEM INHIBITORS
Systems With Coolant Filters
When the vehicle is manufactured, the coolant filter is
equipped with precharge filter element which is larger in size
than the normal service element. The precharge element
contains a sufficient amount of chemical to