GENERAL MOTOR DIESEL LOCOMOTIVE. Manual - part 9

IRCAMTECH/2006/M/D/GM loco/1.0

Introduction hand book on GM locomotive February 2006

chamber of the cylinder head. Outlet water from each cylinder
head goes to the return header (also called water outlet
manifold) which carry water to the radiator.

Each water main header is connected at the rear end

from where a water pipe line carry water to cool the after
cooler. Water from the aftercooler goes to water return header
and through water return header to radiator.

A water pipe line from the water pump carry water to

compressor to cool the compressor liners, cylinder head,
valves and the compressed air inside the inter cooler. Air

compressor cooling is
done whenever engine is
running.

The radiators are

located in a hatch at the
top of the long hood end
of the locomotive. The
hatch contains the
radiator assemblies,
which are grouped in two
banks. Each radiator
bank consists of two
quad length radiator core
assemblies, bolted end-
to-end. Headers are
mounted on the radiator
core to form the inlet and

outlet ends of the radiator assembly, a bypass line is provided
between the inlet and outlet lines in order to reduce velocity in
the radiator tubes.

Two 8-blade 52” cooling fans, which operate

independently, are located under the radiators in the long hood
carbody structure. They are numbered 1, and 2,with the No. 1
fan being closest to the driver cab.

The water pump inlet side is connected to an

expansion tank for makeup water in the water system. The
expansion tank is located in the equipment rack.

IRCAMTECH/2006/M/D/GM loco/1.0

Introduction hand book on GM locomotive February 2006

Temperature control by the cooling system

Mainly the two electronic temperature sensing probes

(ETP1& ETP 2), EM2000 computer and the radiator fans take
part in controlling the water temperature.

Two electronic temperature-sensing probes (ETP1&

ETP 2) are located in the water pipe line between the lube oil
cooler to the inlet of the water pump on the engine left side.
Temperature probe readings are converted by ADA Module
from analog to digital signals which are used by the EM2000 to
control all cooling functions.

Each cooling fan is driven by a two-speed AC motor,

which in turn is powered by the companion alternator. As the
engine coolant temperature rises, the fans are energized in
sequence by the control computer (slow speed). As additional
cooling is required, the fans switch to full speed in progression
as coolant temperature rises. As coolant temperature drops,
the fans switch off one at a time.

The cooling fans are controlled by the computer which

act on the contactors. The computer also controls the fan
sequencing duty cycle and speed (low or high) to ensure even
fan and contactor wear.

The engine water temperature can be observed by a

gauge located on the inlet line to water pump. The gauge is
colour coded to indicate cold (Blue), normal (green) and hot
(red).

When the engine temperature become excessively

high, the EM 2000 will display “HOT ENGINE”- and throttle 6
limit” message. The computer will initiate the reduction in
engine speed and load upto 6

notch. This condition will

remain in effect until the temperature return to safe limit.

If the engine water temperature is below 115

F (46

C), the engine speed will be raised to throttle 2 automatically

by the computer. Once the engine water temperature reaches
above 125

F (52

C), the engine speed will be reduced to

IDLE.

IRCAMTECH/2006/M/D/GM loco/1.0

Introduction hand book on GM locomotive February 2006

The reason for engine speed up will be displayed to the

driver on EM 2000 computer monitor as “Engine speed
increase- low water temperature”.

Cooling System Pressurisation: -

The cooling system is pressurized to raise the boiling

point of cooling water. This in turn permits higher engine
operating temperatures, with a minimum loss of coolant due to
pressurization and also ensures a uniform water flow and
minimizes the possibility of water pump cavitation during
transient high temperature conditions.

A pressure cap, which is located on the water tank-

filling pipe, opens at approximately 20 PSI. It prevents the
damages of cooling system components by relieving
excessive pressure from the system. The pressure cap is
equipped with a handle which helps installing and removing of
the cap. The most important function of the pressure cap
handle is to release pressure developed in the water system
before removing the pressure cap.

GM locomotive Vs Alco locomotive

Although the purpose for which the cooling water

system is designed is same for Alco locomotive and GM
locomotive, but the design of the cooling water system differs
in Alco and GM locomotive in respect of general arrangement,
position of various components, make and design of
components etc. The important comparisons between the two
locomotives are given below-

1. The water system capacity in GM loco is 1045 lts. and in

Alco loco is 1210 lts.

2. Both the locomotives have a closed loop pressurized water

cooling system.

3. Both have radiators but their locations and capacities are

different. In GM loco the radiators are located in a hatch at

IRCAMTECH/2006/M/D/GM loco/1.0

Introduction hand book on GM locomotive February 2006

the top of the long hood end. In Alco loco the radiators are
placed in vertical position in radiator compartment.

4. Both the locomotives have centrifugal type water pump.
5. In GM locomotive 2 water pumps are provided one for right

bank and one for left bank. In Alco locomotive only one
water pump is provided.

6. In GM locomotive Berate nitrate water is used for cooling

water and in Alco locomotive chromate water is used for
cooling water.

7. In GM loco radiator fans operate by electrical motors and

in Alco radiator driven by mechanical power.

8. The expansion tank is located in the equipment rack in GM

loco. In Alco loco the expansion tank is located in radiator
room at the top of the long hood end.

9. Both have pressurization cap which open at approximately

20 PSI.

10. In GM loco, the water system cools the compressor also.

But in Alco loco, the expresser / compressor is air cooled.

11. GM loco has got low water temperature control system. In

Alco, no such system provide.

12. The water temp. control system has EM 2000 computer

and electronic temp. sensing probes ETP1 & ETP2 in GM
loco but in Alco control is done by ETS1, ETS2 and ETS3.

13. In GM loco the turbo charger cooling is done by lubricating

oil but in Alco loco the turbo charger cooled by water
system.

Content .. 7 8 9 10 ..