T&T: Engine temperature

[Rich Gano]

Since you have twins, you have a built-in "control" for testing, if one
assumes the port engine is operating normally.

You have gotten a good work list from other members, and the simple things
they suggest will more than likely adequately address the issue you have.

Sorry if I missed it in somebody else's post, but get a good "infrared"
thermometer from your local NAPA dealer and repeat your test.  You can check
the port engine against the stbd with it, concentrating on the areas of the
coolant temperature senders and the oil coolers and heat exchangers.  If
you'd had one of these essential pieces of gear aboard, you could have
checked the engines when the overheating happened and come away with some
good troubleshooting information.  Another option is to check the gauge
system itself by simply cross-connecting the sending wires by disconnecting
them and running a couple of feet of extension wire to the opposite engine.
BTW, don't confuse the temp sender with the coolant alarm sensor, which for
a FL120 is on the side of the coolant expansion tank.

I don't think anybody mentioned HOW to check for head gasket leak into the
engine coolant.  Look for bubbles in the coolant in the recovery tank when
the engine is running hot.  I won't go into all the necessary precautions,
but you may want to engage a mechanic at this point.  There is specialized
testing apparatus for this.

It's not possible to clean the two oil coolers on a Lehman this way, but I
recently cleaned my main heat exchangers on my two FL120s while they were on
the engines by simply pouring some pool-grade muriatic acid directly in
through the zinc holder hole.  Nice pink cleanliness was later confirmed by
removing the end caps for inspection.  I think this is a lot gentler than
poking rods and rifle cleaning brushes through the tube nest.  Works like
this:  pour acid in until it bubbles over; screw on zinc holder (only takes
a cup or two); immediately start engine and run for five minutes or however
long you want if you are getting underway anyway.  Ten minutes tops and
you're done.  It was not necessary to let the acid sit for any length of
time in the heat exchanger, and running it out immediately means no harm
will come to any or the system downstream.  Note that my heat exchangers are
just barely above the waterline - I personally would not attempt to do this
with exchangers below the water line because of the necessity to shut off
the raw water intake, drain the heat exchanger, etc, etc, which means a
longer stay time for the acid in the heat exchanger before starting the
engine.  I took a spare heat exchanger in to a radiator shop recently for
refurbishment and watched the shop owner do exactly what I did, only he used
a water hose to wash out the tube nest instead of saltwater flow from the
raw water pump like I did.  I wore rubber gloves and face shield as
precautions - he didn't have so much as eyeglasses on.

Rich Gano
CALYPSO (GB-42-295)
Southport, FL