LT1 Coolant Change Procedure

I take no
credit for this info. This info was given when I asked ”how to” and I
thought I’d polish & post it for future reference. Thanks to all for
the help!
LT-1 Coolant Change Procedure:
In order to do a
good flush you have to remove both knock sensors out of the block, which
are on each side of the oil pan. When you go to remove those knock
sensors, use either a 7/8 socket and socket wrench or an offset box-ended
wrench to remove them. They should come off fairly easy if they had
previously been torqued to specs. (The block holds almost 60% of all of
the coolant in the system so this step is necessary to get a good flush)
In the event that you have to ”go gorilla” on the sensors, you can use
a pair of vice-grips to grasp the round base of the sensor. Avoid rounding
off the bolt pattern on the sensor. Resort to the vice grips only as a
last resort, grasping the round base of the sensor. If you damage a
sensor, they run about $35 from your local Chevy dealer.
Stick with the
genuine AC/Delco stuff and don’t use the cheapies from Auto
Zone,
Pep Boys, etc.. since they may be calibrated to different specs
and can cause Trouble Code 43 on your ECM. When reinstalling the knock
sensors, set your torque wrench to 11 to 15 foot lbs.
This is very
important. Too much torque and you will damage the sensor or render
it
useless. Not enough muscle and you will weaken the sensor’s ability to
do its job. (in the event you broke a sensor and are replacing with a new
part… the orange tape that coats the new sensors is all you need. DO NOT
use threading compound or tape when installing the new
sensor)
Removing the fill cap to release the pressure in the
system. It will drain much quicker.
Unscrew the draincock from the
lower passenger side of the radiator. (it does not come all the way out)
It is a good idea to open the brass air breather screws on the
water pump thermostat neck and the underside of the throttle body.
Once you have drained all the old coolant, close up everything and
fill the system from your garden hose. Run it through, empty, fill, run it
through, empty, and you should have a decent flush.
Remove the
coolant overflow tank in the front well and clean it out too.
To
get the coolant system completely full you will have to open the air
breather screws (water pump and throttlebody) to get all the air out.
(HINT— take out the thermostat and fill the block first putting
the fluid in the coolant fill tank. BTW, this would be a good opportunity
to bypass the coolant lines going through the throttle body, and install a
lower temp thermostat. When you start to see fluid filling up the water
pump, close up the housing and fill the rest of the system)
Refill
the cooling system with two jugs of coolant and two jugs of distilled
water. You might also consider adding some ”Water Wetter”. Don’t
forget to refill the overflow tank to the proper level.