MACS Monthly Newsletter - 2020 - DEC9

Electric Water Pumps

techinfo.toyota.com

Figure 13: Toyota was one of the first manufacturers of lower-priced cars to go to
electric water pumps on conventional gasoline engines, a move probably inspired
by its use of electric pumps on its many hybrid vehicles. The electric water pump
offers packaging and control advantages. The labeled parts are: (b) stator, (c) rotor, (d) pump shaft.
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Editors:
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Mobile Air Conditioning Society Worldwide
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Email: membership@macsw.org * Website: www.macsw.org

Unless otherwise noted, all photos/art by author.

December 2020

Figure 14: Dodge Durango was
one of a number of domestic makes
to use an auxiliary electric water
pump. It helped circulate coolant at low engine speed, which
improved cabin heating. Labels
for pump are: 1) rubber isolator,
2) plastic housing, 3) heater hose
connectors, 4) electric DC motor,
5) electrical connector.

MACS Service Reports

techauthority.com

faster than merely a belt drive would produce can improve coolant circulation in hot weather and even engine heating in winter,
when pump output would slow down in low-speed operation.
The electric pump also offers flexibility in its location on the
engine. In fact, it really doesn't have to be on the engine, although mounting it there does shorten hoses and other coolant
plumbing. So, if the pump ever fails, you'll find it a lot easier
to replace than a mechanical pump on the engine and perhaps
requiring removal of a timing belt or chain.
Yes, there were a number of auxiliary electric pumps, going
back many years, to maintain coolant circulation at low engine
rpm and even engine off, for improved heating. That type of
electric pump (Figure 14) is a single speed design, turned on or
off by a simple algorithm. Fiat Chrysler used an on-off auxiliary
pump on a number of models, such as the Dodge Durango V8
through 2006. The algorithm: road speed under 30 mph, coolant
temperature from 50° to 230°F, front blower on, rear HVAC temperature setting more than halfway to heat. The pump circuit
was routed through the A/C heater control panel. The pump
should turn off at road speed above 30 mph, or blower off, or
coolant temperature over 230°F. n

Presumably you've noticed that engine-powered water
pumps on some new models have been going electric (Figure
13). Sure, the changeover started with hybrids, as the water
pump obviously had to keep spinning even in brief all-electric
drive operation. But then the electric pump began to appear on
a few non-hybrid, all-gasoline-powered European models (such
as BMW 2.0-liter four-cylinder engines and in the last four years
on Toyota/Lexus engines). Now we find them on GM conventional gasoline-fueled engines, particularly those with the ATM
(active cooling) systems, as discussed earlier in this report. Sure,
you won't find electric pumps on some makes at this time, but
as an example, Ford is focused on changeover to battery electric
vehicles, and naturally their cooling systems use electric water
pumps for the cooling systems that protect the battery packs,
power electronics and electric motors.
The electric water pump provides a number of advantages.
First, because it's operated by the engine computer, it can run
as fast or as slow as needed for coolant circulation. Running it
as slow as possible obviously saves energy and that translates
to better fuel economy. Maybe it's not a lot, but every little bit
that can be measured (and fuel savings from an electric water
pump is measurable) may be worthwhile. Running the pump

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MACS Monthly Newsletter - 2020

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