Because the engine/thermostat cap is higher than the radiator cap; the complexity of cleaning out ALL the old coolant requires several flushing’s until the drained liquid is nearly colorless. I use distilled water to flush my systems as my 'tap' water has a high mineral content.....
IMHO*DO NOT try to open the plastic radiator drain valve; the plastic stem often breaks or the threads get galled. Leave the plastic radiator drain valve alone.
*Don’t try to open the two drain plugs built into the coolant pipes under the car as these plugs are normally very tight (frozen) and their inter socket of these plugs will strip.
*I don’t waste time on the 2.8L block drain plugs as aren’t accessible (one is under the starter) and are ineffective as considerable amounts of coolant remains.
My '88 Fiero GT Coolant Draining Procedure:The passenger coolant pipe under the car, and 3-inches rearward more from the drain plug; remove the rubber hose (heater core) from the main pipe to start draining the coolant. To avoid the discharge of coolant ejected turbulently; leave the radiator cap and engine/thermostat cap on. After the coolant drained; then open the caps and remove the thermostat.
Without the Thermostat:
*Install the rubber hose (heater core) back on the main coolant pipe
*From the Thermostat Housing; pour clear water watching the radiator opening, when full, cap it
*Pour clear water to fill the thermostat housing, and then cap it enough to seal the housing
*Run the engine 30 seconds, shut it off, open the engine cap, add water and cap it tightly
*Run the engine until the radiator hoses are very warm to circulate the liquid, and then shut it off to cool it down
*Drain it again and fill it up repeatedly until the drained liquid is very clear, my Fiero takes around 8 to 10 flushings.....
Remove the coolant recovery tank, clean it and reinstall it
My Cooling Filling Procedure: If possible, determine the actual fluid capacity of your coolant system. My 2.8L capacity is 13.8 quarts, and the fully flushed coolant system has ~7 quarts of Distilled Water in the engine block/heater core/etc. My next step is to pour ~2 gallons (8 quarts) of
straight full strength concentrate antifreeze,
not a premixed 50/50 because the 'trapped' water in the system.
*From the Thermostat Housing; pour antifreeze watching the radiator opening, when full, cap it
*Pour antifreeze to fill the thermostat housing, and then cap it enough to seal the housing
*Run the engine 30 seconds, shut it off, open the cap, add antifreeze, install new thermostat and cap it tightly
*Pour the remaining of full strength concentrate antifreeze into the coolant recovery tank
*Fill the coolant recovery tank with 50% antifreeze and 50% coolant at the FULL level
*Run the engine until the radiator hoses are very warm and then shut it off to cool it down
Remember, the coolant system has AIR in the radiator! Check the coolant recovery tank and add 50/50 mix if needed to keep the level above the ADD mark.
Run the engine to reach operating temperature and cool it down at least three more cycles before driving the car on a long trip which will ‘burp’ air from the system.
Other members may tell you differently.......
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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles
[This message has been edited by Vintage-Nut (edited 03-24-2024).]
