Additional cooling question

[Robert G.]

I posted a question about coolant with my newly purchased '66 (327/350) and it seems Zerex G-05 at a 50/50 or even 60/40 is the populat choice. New question though, if one removes the thermostat and leaves the housing open (to allow flow) and then the lower radiator hose from the block would that allow the entire block to be drained, or does it have to be drained from the sides.
I do remember in the old days there being machines that would flush the entire system and then replace with a clean mixture.
Rob Goodrich
#65905

[Joe L.]

Re: Additional cooling question

I posted a question about coolant with my newly purchased '66 (327/350) and it seems Zerex G-05 at a 50/50 or even 60/40 is the populat choice. New question though, if one removes the thermostat and leaves the housing open (to allow flow) and then the lower radiator hose from the block would that allow the entire block to be drained, or does it have to be drained from the sides.
I do remember in the old days there being machines that would flush the entire system and then replace with a clean mixture.
Rob Goodrich
#65905

Rob------


Doing what you suggest will not result in all of the coolant being removed from the entire cooling system. The only way to do that is to open the radiator drain (or, alternatively, remove the lower radiator hose) AND remove the block drains.

However, using a Prestone or other "Flush-and-Fill" kit one can flush the system without removing the block drains. Then, after draining the radiator, add the amount of concentrated coolant to give you the % coolant you decide to use based on your car's cooling system capacity, and then add water to get the system to the fill mark on the supply tank. You can follow this procedure if the tap water in your area has very low total dissolved solids (TDS). Otherwise, you'll need to do the complete drain and refill with coolant + distilled or deionized water.

[Ed S.]

Re: Additional cooling question

You have to remove the plugs from each side of the block to get all the coolant out of the block. Best way to "drain" the system (Small Block) is: Remove the thermostat - then replace the goose neck sans thermostat. Loosen the drain plugs on each side of the block - not easy if they haven't been moved in years. Plan on replacing them with new ones as the hex head gets damaged some. Move the heater controls to the ON or open position. Start the car, then remove the drain plugs and provide a supply of water (from a hose to the radiator or surge tank - let the engine run and watch the color of the coolant coming from the drain plug holes - once it is clean turn off the engine - open the pet cock at the bottom of the radiator. Replace the drain plugs in the block - replace the thermostat. Fill with 50 /50 mix of coolant & H2O, run till engine is warm and then check fluid level again. Note that when you remove the drain plugs from the block the first time there may be gunk built up in the holes so bad that fluid does not flow from them - just take a small screw drive and poke the gunk, fluid will come gushing out. I would also replace the thermostat with one that is designed to fail in the open position. The brand is FlowKooler - made in the USA - you can find threads on this forum about them. Not expensive.

[Joe L.]

Re: Additional cooling question

You have to remove the plugs from each side of the block to get all the coolant out of the block. Best way to "drain" the system (Small Block) is: Remove the thermostat - then replace the goose neck sans thermostat. Loosen the drain plugs on each side of the block - not easy if they haven't been moved in years. Plan on replacing them with new ones as the hex head gets damaged some. Move the heater controls to the ON or open position. Start the car, then remove the drain plugs and provide a supply of water (from a hose to the radiator or surge tank - let the engine run and watch the color of the coolant coming from the drain plug holes - once it is clean turn off the engine - open the pet cock at the bottom of the radiator. Replace the drain plugs in the block - replace the thermostat. Fill with 50 /50 mix of coolant & H2O, run till engine is warm and then check fluid level again. Note that when you remove the drain plugs from the block the first time there may be gunk built up in the holes so bad that fluid does not flow from them - just take a small screw drive and poke the gunk, fluid will come gushing out. I would also replace the thermostat with one that is designed to fail in the open position. The brand is FlowKooler - made in the USA - you can find threads on this forum about them. Not expensive.

Ed------

One small correction: most Corvettes, except A/C equipped, do not have valves in the heater coolant circuit. There is always flow through the heater core and heat to the cabin is controlled by an air valve ("door"). So, for most it's not necessary to move the heater controls to on.

[Ed S.]

Re: Additional cooling question

Ed------

One small correction: most Corvettes, except A/C equipped, do not have valves in the heater coolant circuit. There is always flow through the heater core and heat to the cabin is controlled by an air valve ("door"). So, for most it's not necessary to move the heater controls to on.

You're right! The instrument panel "heater control" knob on a C2 does not operate a water control valve - it just opens or closes a trap door that controls air flow over the heater core. Thanks for reminding me of that point - don't know what I was thinking.

[William F.]

Re: Additional cooling question

It does on a 67 with AC . Vacuum opens a valve that admits water to flow through heater core. at least some year Non ac C2's have water flowing all the time.