MACS Service Reports - 2015 - JAN3

Paul Weissler

operation. Particularly on an older car, perfection isn't
necessary, just results that are good enough to satisfy a
customer for whom a heater core replacement might cost
more than he'd be willing to spend. Unlike A/C, plugged
heaters are rarely seen on cars seven years or younger. It
happens, but most are on older models.
Here's an example worth noting: a 2006 Honda Pilot
with the complaint that the air coming out of the vents is
warm, but not hot enough to produce a comfortable cabin. The technician checks the heater in and out temperatures at the hose necks, and they're 180°F and 154°F. So
the problem obviously is not related to coolant temperature itself. But that 26 degree temperature drop is huge.
Often we see as little as 3 to 5 degrees, and certainly less
than 10 degrees when there's good flow. The technician
began by using a full strength chemical flush through the
core only multiple times, and then switched to power
back flushing for an hour with water only, and finally with
power back flushing through the entire cooling system.
The results were decent for the investment. With good
equipment, a lot of the flushing time doesn't require continuous attention, and the motorist was very satisfied. Of course
the Pilot heater core replacement is a labor-intensive opera-

hondatechinfo.com

Figure 5: After several more attempts at back flushing, the probe in the
floor air duct shows the temperature is now very good, hitting 155°F.

Figure 7: Replacement of a Honda Pilot heater core is a last choice job, because it requires a lot of time, including taking out the dashboard to be able
to remove the HVAC case as shown.

Hecat Inc

tion, flat rated at about nine to ten hours (including heater
hose replacements, cooling system flush and fill, as well as
air conditioning recovery and recharge). Yes, the job also requires removal of the dashboard, the HVAC units (including
the heater case) and of course the evaporator (Figure 7). That
makes it one tough job, and for a first-timer on this vehicle,
add a few hours to that labor time. Including the cost of the
OE heater core (you wouldn't take a chance with anything
else for this big a job) can bring the total up to a number that
might floor a customer.
That doesn't mean you should only go for the intensive
flush if the job is this expensive or very close. However, as
we've noted, very few heater core replacements are pocket
change, and a specialist should be able to offer this kind of
lower-cost alternative. It's still a worthwhile amount of la-

Figure 6: Back flushing with a flush and fill machine or a pulsating
flusher as shown, is likely to yield the best results.

improvement. See Figures 3, 4, & 5.
That means perhaps circulating a flushing chemical
through the system, then using a flush and fill machine
(not just a drain and fill machine) or at least a back flush
gun like the Hecat/Gates pulsating flusher (Figure 6). We
have seen enough cases where it took circulating flushing solvent to start the process, then 3 to 5 operations
with back flushing equipment to provide decent heater

January 2015

MACS Service Reports

http://www.hondatechinfo.com

Table of Contents for the Digital Edition of MACS Service Reports - 2015