Cooling system flush questions

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KCusick81

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Hey everybody,

So after an arduous few weeks of burning the candle at both ends, working 10-12 hour days, prepping my house to go on the market, waiting for parts and fighting daylight, I've finally completed the install portion of my repairs. Today I began the process of flushing the cooling system and have some questions about how to proceed. I have replaced the entire cooling system with exception of the radiator. Because it appears to be brand new or very close to it. Today I pulled the block drain and knock sensor and hooked up the prestone flush and fill kit. I ran clear hoses from the radiator drain and block drains into an extra large catch jug to avoid the mess and so I could see when the water ran clear. I turned on the hose and flushed until I saw the water run clear. I did not run the engine during this process. I then took the garden hose and ran it directly into the radiator fill neck and let it run for a few minutes, for good measure. Since the only things that really need flushing at this point are the radiator and manifold. Everything else is new. I was considering pulling the thermostat and flushing directly through the manifold too. The previous owner was running green coolant in the truck and per the advice I got here, I'm switching to dexcool. I also picked up some prestone flush and cleaner. I was planning on doing that next and then flushing one last time with water. Also, I have already removed and thoroughly rinsed the coolant reservoir. Will this be sufficient to ensure all the old green coolant is out of the system? Is the prestone flush chemical safe to use on our trucks? Or should I skip that step? Is there anything I'm missing or anything I should do differently? I really just want to get this right the first time and get my baby back on the road! Any help suggestions and information are greatly appreciated. Thank you in advance.

Kyle
 

454cid

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If your heater circuit goes back the radiator, and not the water pump, you're not getting much circulation though the engine with the Prestone flushing kit. Having those block drains is a good idea, Though. That's what I need to do with mine.
 

Frank Enstein

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I think you said you didn't run the engine. Long day.

I take the upper hose off the radiator, add some tubing so when it barfs it doesn't make a mess, put a gutted thermostat in it, stuff the garden hose in the rad fill, and let it idle until clear water comes out of the cobbled up radiator extension.
Adjust the hose volume to allow a bit of water to come out of the upper hose connection @ the radiator so the engine stays full.

I like the Justice Brother's radiator cleaner. Nearly impossible to find but it's the best stuff I ever tried.
 

Schurkey

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I use Prestone Flush and Fill kits, but I make sure to run the engine while the water is flowing. That way the water pump stirs-up the clean water and creates turbulence in the engine water jacket, so the clean water "scrubs" the inside of the engine. I occasionally whack the throttle open to 2500 rpm and then allow it to idle.

I would need a ginormous drain pan when flushing; realistically no drain pan is huge enough to hold all the clean water I use. However, I'd capture the original coolant drained from the rad draincock and the two block drains for appropriate disposal.
 

L31MaxExpress

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Hey everybody,

So after an arduous few weeks of burning the candle at both ends, working 10-12 hour days, prepping my house to go on the market, waiting for parts and fighting daylight, I've finally completed the install portion of my repairs. Today I began the process of flushing the cooling system and have some questions about how to proceed. I have replaced the entire cooling system with exception of the radiator. Because it appears to be brand new or very close to it. Today I pulled the block drain and knock sensor and hooked up the prestone flush and fill kit. I ran clear hoses from the radiator drain and block drains into an extra large catch jug to avoid the mess and so I could see when the water ran clear. I turned on the hose and flushed until I saw the water run clear. I did not run the engine during this process. I then took the garden hose and ran it directly into the radiator fill neck and let it run for a few minutes, for good measure. Since the only things that really need flushing at this point are the radiator and manifold. Everything else is new. I was considering pulling the thermostat and flushing directly through the manifold too. The previous owner was running green coolant in the truck and per the advice I got here, I'm switching to dexcool. I also picked up some prestone flush and cleaner. I was planning on doing that next and then flushing one last time with water. Also, I have already removed and thoroughly rinsed the coolant reservoir. Will this be sufficient to ensure all the old green coolant is out of the system? Is the prestone flush chemical safe to use on our trucks? Or should I skip that step? Is there anything I'm missing or anything I should do differently? I really just want to get this right the first time and get my baby back on the road! Any help suggestions and information are greatly appreciated. Thank you in advance.

Kyle
Personally I stay far away from Dexcool. Stuff is terrible. I use big truck coolant and have for years. Took me one look at a sludged coolant system and then I noticed most GM cooling systems with Dexcool were sludged when I opened them. I have seen it plug heater cores, stop up radiators, build silt in engine coolant passageways. It turns into almost a sandy algae like consistency that is dark orange in color.
 

Donald Mitchell

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Personally I stay far away from Dexcool. Stuff is terrible. I use big truck coolant and have for years. Took me one look at a sludged coolant system and then I noticed most GM cooling systems with Dexcool were sludged when I opened them. I have seen it plug heater cores, stop up radiators, build silt in engine coolant passageways. It turns into almost a sandy algae like consistency that is dark orange in color.
That' what I've been told, and was curious why he was changing from green to dexcool.
 

df2x4

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I run Dexcool in any vehicle that originally called for it. I've only had one issue with it getting nasty, and that was in a vehicle that hadn't had the coolant changed in nearly a decade. IMO there's nothing wrong with Dexcool as long as you make sure and change it every 4-5 years. Both of my '97s are still running it.
 

95burban

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Personally I stay far away from Dexcool. Stuff is terrible. I use big truck coolant and have for years. Took me one look at a sludged coolant system and then I noticed most GM cooling systems with Dexcool were sludged when I opened them. I have seen it plug heater cores, stop up radiators, build silt in engine coolant passageways. It turns into almost a sandy algae like consistency that is dark orange in color.
Your correct. I run pink CAT ELC coolant in everything. Mostly because it’s readily available and it fights electrolysis.

As for system flush, I’ve used a lot of crazy stuff. Cascade for dishwashers, mineral spirits, degreaser etc. I would use at your own discretion but my point is not to put much thought into it. Drain, fill, drive repeat a few times and your good.
 
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