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Back to basics - elementary question - Changing coolant

badmix

badmix

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Okay, its time to flush/drain/refill my coolant in my '83 K5. It hasnt been done in a long time and Im going to change thermostat and rad. cap as well. Now, what is the correct, best, easiest procedure for doing a complete flush on the coolant system?

Ive heard some various ways, one being pull the thermostat and run clean water thru the whole system, drain and then refill with 50/50mix, etc.

Any other approaches?

Thanks
 
Pull the drain plugs on the sides of the block just above the oil pan. Run water through the block with a hose while those are out, might be able to get silt and junk out that way.

Plus, draining the water that way ensures that whatever water/antifreeze mix you want ends up being accurate and not diluted by water or coolant sitting in the lower portions of the block.
 
I've actually never done it that way...never kept any of my vehicles long enough to need it, but now that I think about it, my truck does need the coolant changed.

I'd probably suck most of the coolant out with a hose down the radiator, then go for the drain plug(s). Is the problem that there is stuff in the way that the coolant hits, no way to move a bucket or something up high enough to catch it right near the hole?
 
you can hold a funnel up to it, to divert it past the crossmember the first time.. Then when emptied, put a petcock in, so you can hook a hose to it the next time you feel the need...
 
my friends truck is a 80s m1009. the lower hose has been cut. some pipe was put in with a petcock in the middle. looks home made. seems like a good idea tho. hope this helps
 
Use demineralized water. The system won't load-up with junk if you don't put it in, and it will nearly eliminate corrosion.
 
Well I changed my coolant. Here is how I did it, Im sure it was the best way, but it was the easiest.

1) Drained radiator

2) PUlled bottom rad. hose off water pump

3) Pulled top hose to thermostat

4) Pulled thermostat housing and thermo.

5) With the drain plug out, I ran a house thru the radiator for about 20minutes

6) with the thermostat and the water pump house off, I ran a house down the INtake manifold for about 20minutes. I dont know if this was a direct pass out to the bottom or not. So I may not have gotten the block totally flushed. I wasnt going to pull the plugs on the sides. Ill do that next go around.

I ended up replacing the thermostat housing, it was the org. one and it was pretty bad, it was corroded and was jus begging to start leaking.

I pulled , flushed and cleaned the overflow tank, it literally had what looked like MUD in the bottom of the tank, it was clumps of something.

Anyways, when I did all this. I put it all back together and ended up only putting 1 gal. of deminilized water and 1/2 gal. of coolant. I started it up and put Heat on. I kept an eye on it with the cap off. TO get air bubbles out. Drove it around, let it cool down and checked it, it was fine. Temp gauge read normal 195degree.

My question is, I thought this system was a 4 gal. system. Im guessing there was a bunch of water in the block left over and in the heater core?
 
shoulda pulled the block plugs... holds the majority of the coolant.. makes all the difference in the world, thats where the sediment likes to settle..

ya gotta realize all you really did was change some of the antifreeze... cold water flushing really wont do much...

I don't even pull hoses... take off rad cap, pull block drains, drain, reinstall. fill with water, run to hot, take rad cap off, pull plugs, drain. repeat...

If you really want it clean, put about 10% muriatic acid in with the water (just need to be careful with aluminum parts)..

I'm sure what you did will be a vast improvement.. Thats just how I go about it..
 
Ok. Thanks. Ill definetly do it that way next go around, if I get bored I may do it sooner. Im only out 1/2 gal. of coolant really. Are the plugs on both sides of the block? what do they look like and are jus push in freeze plugs or some screw in/out deal.
 
Usually just hexhead NPT plugs, couple inches above the pan.. 9/16th's wrench or socket...
 
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