CHANGING A WATER PUMP ON A CAT 3116 DIESEL ENGINE

We have 13 Caterpillar 3116 diesel engines in our school bus fleet, a well built engine with a unique fuel system, unit type injectors connected to a rack mechanism that's controlled by a governor. However they do have a weak spot, namely the exhaust valves.

There have been a few instances of a dropped valve in the cylinder head [the exhaust valve breaks to pieces] this causes damage to the piston and head. So off comes the head for exchange and our 'fingers are crossed', hoping for minimal damage to the cylinder walls and turbo. That story may surface in a future posting.
Water pump replacement is an easy job, as you can see it's located at the front of the engine. This 3116 is in a Thomas ER model [pusher] school bus.
With coolant drained, remove idler pulley, hoses, drive belt and 4 retaining bolts. Water pump is now ready for replacement with the exchange unit.

NOTE: The water pump belt runs on an idler pulley that's used to adjust belt tension. Check the idler pulley bearings and the pulley for wear. We've had some bearing failures in the past but now we make a point of checking them on a regular basis. The bearing itself is easy to replace and common enough to be found at any bearing distributor.The Cat distributor can get us a reman water pump overnight but in this case we stock one at all times because of this recurring failure. The most common problem is the bearing seal which causes a coolant leak out the pump body just behind the pulley.

Once reassembled we do running checks before releasing the bus. The best way to purge the air out of the cooling system is taking the bus for a good roadtest to allow the thermostat to open fully.

These school buses have approxiamately 18 to 20 litres of coolant in the cooling system running through 1 inch heater hoses to numerous interior heater cores. So there are lots of pockets of air when the coolant is totally drained.

RECOMMENDED READING:

Motor Oil & Filtration

Trust My Mechanic