MACS Monthly Newsletter - 2017 - MAY4

Photo Dave Hobbs

Courtesy Extech Instruments

Courtesy Pete Meier / Motor Age

Figure 5, 6 and 7: Any good PM (Preliminary Maintenance) program includes checking the freeze protection of coolant and PH levels. < 7 is considered
acidic. Checking the voltage of the coolant is a good item for the PM list as well. It backs up the PH test. Chloride is in city water and can cause corrosion in
a cooling system. That means the coolant's PH moves into the acidic region. Dissimilar metals in the system then allow that acidic coolant to create a small
amount of voltage. Simply ground your DC meter's black lead and drop the red lead down into the coolant. If you measure > 0.3 volts, that cooling system
has a corrosive problem. Regarding freeze protection testing, hydrometers are still utilized by many techs but are rapidly losing ground to more accurate
and versatile refractometers. Some refractometers check both EG and PG coolants as well as the specific gravity of a battery's electrolyte for an accurate state
of charge. The particular model in the photo on the left can also check the freeze protection of windshield washer fluid and DEF (Diesel Emissions Fluid).
Refractometers are used in other industries as well for everything from sugar content in grapes to the salinity of water. Refractometers are simple to use. Pop
up the hinged plastic shield covering the optic's flat surface. Drop a few drops of coolant on to the optic and close the plastic cover. Hold the eye piece up to
your eye and look through it like a telescope. A good EG based coolant should be -34 degrees F with the proper 50/50 water mix. If the freeze point measured
is higher (i.e. -20 F) typically too much water is in the mix while excessively lower (i.e. -40 F) means too much antifreeze concentration.

coolers on the market but you still need to get the correct
coolant with the best water to prevent comebacks. Distilled is good! Use it for every cooling system you work
on unless you strictly use premix.

isn't as much of a problem for the cooling of the
engine as it is for other coolant uses such as high
voltage components on Electric Vehicles (EVs) and
Hybrid Electric Vehicles (HEVs) due to the conductive nature of the water you might choose to use. It
is true, engineers don't run coolant directly across
HV (High Voltage) battery cells. Nor do they allow
those high current super-fast solid state switches
referred to as IGBTs (Insulated Gate Bipolar Transistors) to swim in coolant. Heat sinks to run the
coolant through are used to remove the heat from
these very hard working components commonly referred to as 'power electronics'. The same is true
for the motor / generators inside the transaxle or
mounted to the engine via a drive belt (GM BAS
- Belt Alternator Starter). Engineers and the technicians who work on these amazingly complex vehicles want safety as the number one goal in vehicles
sporting enough voltage and current to run a small
house. Seals between components such as inverters
(changing AC-DC and vice versa) and DC-DC converters (basically the 'solid state' alternator used on
all EVs and HEVs) do tend to leak a tiny bit over
time. For this reason, GM released a Preliminary
Information (PI) document to advise technicians
to use Deionized water ONLY in the high voltage
related section of the Chevy Volt's cooling system.
(Fig. 8)

Preventative Maintenance
Getting your customers into the A/C season also
means getting them into a more demanding engine
cooling season. Pressure testing, coolant (visual)
condition, freeze point determination, (Fig. 5 & 6)
along with using test strips (Fig. 7) to check the
coolant's PH level is a best practice to say the least.

With High Voltage - DI (Deionized) is Better!
Distilled water has long been the choice for steam
irons, CPAP medical devices, cool mist humidifiers
and of course automotive cooling systems especially in areas where tap water from a well or even city
water is known for its hardness. Hard water has a
high mineral / sediment content. The minerals can
cause sediment build up restricting flow and even
have the potential to react (chemically) with the
coolant's additive package.
The problem with distillation is the minerals don't
all have the same boiling point as the water. This
results in water that still has some organic minerals in it. Those organic minerals are basically from
the soil and are known to be conductive ions. This

May 2017

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017