MACS Monthly Newsletter - 2020 - FEB6

A NEW WORLD OF COOLING SYSTEMS

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You probably haven't seen many late-model superhigh-performance vehicles in your shop, or even latemodel premium European cars (and likely won't for a
number of years to come). So, models with multiple radiators combined with variable-speed electric water pumps
will not have appeared and changed your impression of
cooling system design. Probably all you may have seen
is the computer-controlled variable speed electric water
pump, which has been used on hybrids for several years
and more recently by BMW (2.0-liter four-cylinder) and
Toyota on new Camry models.
But when an advanced cooling system makes its debut on "mainstream" so-called "conventional" gasoline
engines, it's time to really pay attention.
General Motors has begun a changeover to what it calls
"Active Thermal Management," on the base engine in its
Silverado pickup. The engine is the 2.7-liter in-line four,
which matches in displacement (although not in the number of cylinders) with the 2.7-liter V6 in the Ford F-150.
SAE International has been running a Thermal Management Systems Symposium for a number of years, and
it's been a sign of engineering to come, so MACS staff
members have been attending, to be ready for the new
technology.
Precision cooling isn't limited to internal combustion
engines. Battery electric vehicle cooling may be even
more complex, as high-rate battery pack charging comes
into use, but for the present, let's look at GM's new cooling system for the 2.7-liter four-cylinder, and how different it will be to service.
The system doesn't have a thermostat, so if you suddenly are thinking, "Hey, that's the part I've replaced
most in cooling system service over the years, followed
by radiator, hoses, belt and water pump." Well, relax. It
has lots of parts.

Figure 9: Left side of 2.7-liter four shows the two-valve
assembly with hoses and piping to the engine. Piping also
goes to water pump on other side of engine.

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There's an electric water pump on the right side of the
engine. And as the illustrations show (Figures 8 and 9),
there's a lot of external hoses and piping, but the pump
itself, as an electric motor-driven device, does not have
a belt wrapped around it. Although the water pump's
electrical control (by the engine computer) means it's
infinitely variable and perhaps more subject to failure,
it's also more accessible for service than the integrated
mechanical pumps on some conventional engines. And
although the thermostat may be gone, there's a massive
coolant control valve on the left side of the engine (which
is actually a combination of two valves).
One valve section is integrated with a hot coolant manifold, which controls the flow to the radiator, a bypass
circuit, and engine oil and transmission oil heating or
cooling circuits, using one actuator. It's this valve that not
only regulates engine warmup, but is a primary factor in
eliminating the need for the thermostat.
The second valve, called a "block valve," has a separate
actuator that regulates coolant flow for engine block temperature control as well as to the passenger compartment
heater.
The valves' electric actuators both are on a "LIN" (Local Interconnect Network) to the engine computer (Figure 10). A LIN is a relatively simple network. Although
the valves are not covered by trouble codes, the system
includes trouble-code covered temperature sensors (10
of them) and along with how-it-works descriptions and
which and when coolant circuits have flow and which
don't, the diagnosis should be straightforward. If the
valve assembly has to be replaced, it must go through a
learning curve, which is on the factory scan tool menu. At
this early stage there are probably no detail parts available, such as an actuator, although eventually we suspect
there will be.

Figure 8: Right side of 2.7-liter in-line four-cylinder engine for Chevy Silverado pickup has electric water pump
at lower front, and hoses/piping into the engine and connecting (across the underside of the engine) to a computercontrolled valve assembly.

February 2020

MACS Service Reports

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MACS Monthly Newsletter - 2020

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