Flushing old Coolant from Engine
Working on bringing my newly aquired 67 L71 Coupe back to life. Has been sitting since 2003. Drained the fuel tank, changed the oil and filter, primed the engine, new plugs/wires/rotor, and adjusted the valves. The Cooling System has issues. Pulled the the Thermostat Housing off and both sides of thermostat was full of green crystalized crud. Drained the block and the coolant there looked OK. I'm concerned about the Intake / Gaskets, etc. My plan is to back flush the Engine and Heater Core. Looking for some good tips. Thanks!
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John Evans
Jack Evans Chevrolet
Front Royal, Va
www.jechevy.com
67 L79 Coupe - owned since 1978
67 L71 Coupe - owned since 2011 -
Re: Flushing old Coolant from Engine
You need to get the block drain plugs out. There's two of them. One on each side in the middle of the block, just above the oil pan rail. They can be stubborn, and if you mung up the head, you'll never get them out. Use a 6 sided socket. Put some anti-seize on the plug when you replace it.
Take out the thermostat. Open the radiator petcock. Take off both heater hoses. Open the temp control on the heater panel. Jam your garden hose into one, then the other, heater hose. Jam your hose in the thermostat housing opening. Jam the hose in the top radiator hose.
Your FLAPS sells a flushing solvent for this purpose. Prestone was one maker. You put them in your cooling system and drive around for a bit. I don't know if they work. I just use lots of running water from a garden hose with moderate pressure. -
Re: Flushing old Coolant from Engine
Once you get to the point of driving around I would put in some RMI-25 as a coolant flush. I get it off the Internet (Google it) and it works very well for me.TerryComment
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Re: Flushing old Coolant from Engine
Yes it is. I use it in my DD ALL of which (all three of them) have aluminum radiators and one of which has an aluminum block (see the sig). The instructions say it can be added to the coolant and run full time, but I don't do that. The Caprices have a flow restrictor in the heater coolant circuit that is notorious for clogging and resulting in no or low heat. No such issues in my high-mileage DDs but every 2 to 3 years I change the HOAT coolant (Zerex G-05) and flush with RMI-25. Both Caprices are closing in on a quarter million miles with just this kind of routine maintenance.TerryComment
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Re: Flushing old Coolant from Engine
John,
I bet you cooling system is fine. The thermostat gasket probably leaked some and allowed air to enter causing the corrosion around the stat. If the coolant looks OK coming from the radiator and engine I would run it with 50% G-05 and distilled water available in grocery store and see how the temperature is.
Make sure all the hose connections are snug and the system is topped off full, sometimes it takes some cycles to rid the air from the top of the radiator. You may want to drill a small .040 hole in the thermostat as this will let air escape from engine and out top hose to radiator. At that point it's important to be sure system is filled enough to push air from top of radiator through the small overflow hose to expansion tank.
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