C3 Radiator flush procedure

[jeff72]

Hello -looking for some quidance on changing the radiator fluid in my 72 before the WI winter strikes full force.

I read in popular mechanics to drain the old fluid -fill with water -run the engine until the thermostat opens -drain, fill again -run the engine, then drain and fill with radiator fluid -top off with water.

the article indicated that it would be politially incorrect to flush it with a hose and let it run out into the street. :ugh

does this sound like a good method to anyone -the article states that the above procedure would purge 99% of the old fluid.

thanks

 

[Jack]

The "radiator fluid" is more commonly referred to as coolant or antifreeze. Pets seem to like the sweet taste of antifreeze ... and it can be lethally poisonous. You can drain it hot ... but DO let the motor cool for an hour before you pour water or coolant into it. Suggest you flush with water 2-3 times ... not just once. Also, your cooling system will last longer and perform better if you do not refill with tap water ... flushing w/ tap water OK ... but best to use distilled water for refill /or topoff ... DIH2O about seventy cents/gal at grocery store. True, not supposed to let it run into street ... but ... so long as it's diluted with lotsa water ... and pets CANNOT get to it for a drink ... I won't tell.
JACK:gap

 

[jeff72]

The "radiator fluid" is more commonly referred to as coolant or antifreeze. Pets seem to like the sweet taste of antifreeze ... and it can be lethally poisonous. You can drain it hot ... but DO let the motor cool for an hour before you pour water or coolant into it. Suggest you flush with water 2-3 times ... not just once. Also, your cooling system will last longer and perform better if you do not refill with tap water ... flushing w/ tap water OK ... but best to use distilled water for refill /or topoff ... DIH2O about seventy cents/gal at grocery store. True, not supposed to let it run into street ... but ... so long as it's diluted with lotsa water ... and pets CANNOT get to it for a drink ... I won't tell.
JACK:gap

Thanks Jack,

Let me ask a few in-between questions. What are your thoughts on the Prestone Flush products? -worth using? -or don't bother with.

How long do you flush with the hose? -or is that what you mean by 2-3 times.

after the flush, put in the coolant and then top off with distilled water...correct?. I know it's not a good idea to put well water in the radiator, but doesn't distilled water tend to leach out the metal?

I plan to do this before the hard winter comes which is likely in the next 5 minutes here in WI -is that a bad idea ? or wait til summer -i have no idea how long its been since the last flush -I've owned her for 2 years -put about 100 miles on it since.

Lots of questions -but I'm a stickler for doing it right and accurate.

Thanks for your help -I really appreciate the advice.


jeff

 

[JohnZ]

To do a thorough job, you should also remove the side block drain plugs (about 3/4" above the pan rail, one on each side); those are the ONLY drains for the cylinder water jackets, and all manner of crud collects in them - have to do both sides, as they're not cross-connected. Use a six-point socket to remove them, and use a little anti-seize when you re-install them to ease removal next time (they're NPT pipe plugs).

 

[jeff72]

To do a thorough job, you should also remove the side block drain plugs (about 3/4" above the pan rail, one on each side); those are the ONLY drains for the cylinder water jackets, and all manner of crud collects in them - have to do both sides, as they're not cross-connected. Use a six-point socket to remove them, and use a little anti-seize when you re-install them to ease removal next time (they're NPT pipe plugs).

Great info -thanks

 

[Jack]

To do a thorough job, you should also remove the side block drain plugs (about 3/4" above the pan rail, one on each side); those are the ONLY drains for the cylinder water jackets, and all manner of crud collects in them - have to do both sides, as they're not cross-connected. Use a six-point socket to remove them, and use a little anti-seize when you re-install them to ease removal next time (they're NPT pipe plugs).

So true!

Also ... if those side block drain plugs haven't been removed for a long time ... they can be very difficult to remove. I've had to use a torch to heat the area on some.
JACK:gap
-edit-check this CAC thread for info on Prestone AS100P powder flush & applicable GM P/N & GM service bulletin.http://corvetteactioncenter.com/forums/showthread.php?t=24337&highlight=prestone