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jim larson


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Flushing engine and Replacing coolant
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Well I am thinking it might be time to do this when it warms up.  I got the car in 2004 and don't know if the engine has been flushed or not since it was previously rebuilt or forever.  I have replace the radiator with an old harrison radiator that  had a core replacement or not; but the radiator was flushed at that time.  I have not replace the coolant except for loses when removing radiator at various time.  Probably only about 20,000 miles since 04.

So first question would be, do I try to flush the engine?  Or just replace as much of the coolant as possible?  Then how the best to do that. I watched a video on youtube about flushing both the engine and radiator, then driving the car for about a week with no thermostat, then put in a new thermostat and add coolant.  Or how do I just replace as much coolant as possible.  Add your thoughts.  Thanks



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Jim L

Lake City
Enganeer


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Remove the radiator cap and look inside. If you see some mineral build inside, flush, if not just change out.

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John E - Rogers, MN

Instructions? All I need is the exploded view.
70 El Camino soon to be ls1/t56
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Bobs_Place


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I would say, your a little over due, the original old green fluid that we all used should be changed every 2 years.tsktsk I know I never kept up with that.boring There are "Extended Life" coolants that go out to 5 year interval. Do like Enganeer said, check the radiator, go from there, but i always try to get the block drains out, there will be a lot of coolant left in the engine if you just drain the rad. My Chevelle needs about gallons total. If the radiator looks good I would rinse with water, drain and refill with a prediluted ELC. Don,t use dexcool or similar as they are not recommended for a copper/brass radiator. 



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Bob W.

Lino Lakes
Lost in the 60s


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I usually pull the block drain plugs and install drain valves, if they fit around the motor mounts. They are the same as in the radiator and are available at NAPA, and some other automotive stores. That makes draining later easy...messy, but easy for a complete drain. I start it at a slow drizzle into a drain pan to keep the floor dry.

To flush the block, you can remove the heater hose at the water pump and hold a garden hose at moderate pressure to the heater hose and back flush thru the heater core. Remove the thermostat and put the housing back on. Remove the upper hose from the radiator, so you aren't pushing all the "crap" into the rad. You'll need a nipple cap over the water pump nipple that the heater hose was on. Those are available at NAPA in 5/8 and 3/4". The return hose to the water pump should 3/4".

When I worked in service stations, we always put a can of rust inhibitor/water pump lube in after any cooling system drain/repair. I believe it helps and haven't been able to find anything like that on most auto store shelves anymore. I found it on Amazon at ~ $7 a can. I was going to order a few and then noticed another supplier who sold a whole case of twelve for $28...Say what, 12 cans for the price of 4 ??? That is what I call a "no brainer", so I now have a few cans I can sell to others for a few dollars.



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Mitch D.   River Falls, WI

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1966 Chevelle SS 396 M20

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jim larson


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Sounds like a sale in March.  So I start by slowly draining the radiator and then remove or replace one or more of the block drain plugs.  Then remove the heater hose from the water pump nipple, putting a plug over the nipple. Then remove thermostat and reinstall the thermostat housing without thermostat and hook up a hose to drain.  Then force water through the heater hose, though the heater core, back to the intake, and into the block and out the thermostat housing, (with or without drain valves in the block ?)?  Then fill radiator and block with water.  Run for a while and make sure system is full with no air gaps.  Then drain radiator, install thermostat, and add coolant.  Specifications say system has 22 quarts.  Would it be better to just add say 8 qts and the add more before the winter?



-- Edited by jim larson on Saturday 23rd of February 2019 04:46:15 PM

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Jim L

Lake City
jim larson


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Enganeer wrote:

Remove the radiator cap and look inside. If you see some mineral build inside, flush, if not just change out.

 I guess i don't really know  how much build up is acceptable.



-- Edited by jim larson on Saturday 23rd of February 2019 04:47:56 PM



-- Edited by jim larson on Sunday 24th of February 2019 09:07:26 AM

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Jim L

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