Hi all, at some point I'll need to change out the coolant in my 2015 Z51. I've found the procedure for draining the radiator. My question is, do LT1 engines have engine coolant block drains that should be opened and drained whenever replacing the old coolant.




As shown above (1966 L79, passenger side), I've always done this on my '60's Chevy engines but the LT1 is new to me. Is draining the engine block a routine procedure when periodically replacing coolant on the LT1?

Thank you.

Thomas

 

It is easier to just run clear drinking water through the system until the drained fluid looks clear. Opening the block still doesn't guarantee all of the old coolant gets out of the heater core. Drain the system by opening the radiator, refill and let engine idle until thermostat opens, drain again and refill while engine is running and wait for thermostat to open again, let run for a couple of minutes and repeat procedure until drained fluid is just as clear as what you put in. Then close radiator petcock, add the proper amount of Dexcool to get a 40/60 ratio of water to Dex and top off with clear drinkable water. Stock water to coolant ratio is 40/60 since the C7 came out.

Luckily, with modern GM cars this only has to be done once every 5 years or 150K miles which ever comes sooner. Don't need to follow that ancient two year change over that was necessary for the green stuff. I have done the 5 year cycle on several GM vehicles and last year I just did the third change on my 2003 Tahoe that I have owned since new. Even with a cast iron engine block the old coolant looked just like brand new coolant. Would never see that with the old green stuff which would get dark red over a two year period due to all of the corrosion occurring in the engine.

The biggest thing is I haven't changed any of the Tahoe's cooling system components in all of these years. Hoses, radiator, water pump, heater core are all factory originals. Couldn't do that with any of the 60s cars. The only cooling system component I have had to change since sometime in the 1990s was the water pump on my C6Z which sprang a leak. The DexCool world is far better than the old stuff.

Bill

 

Great Bill, thank you for that quick, comprehensive reply. On my mid-year Corvettes (both 1966's) I not only drain the block to get as much coolant out as possible, but also to help flush the block coolant passages. From your reply I gather these newer engines run much cleaner so that block drain step is not as necessary.

I do appreciate the information. Cheers.

Thomas