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Heater core FLUSH ?

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Old Jul 25, 2025 | 01:45 PM
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Default Heater core FLUSH ?

Winter rig maintenance time. 2004 chevy engine gets up to temp quick, but Cabin HEAT is very slow to come up... 20 minutes to get defrost.
Prior history is that original owner had CRACKED CAST-TEch head(s) on LM7 and used every brand of stop leak and engine block sealer on the market.... and THEN parked the vehicle for several years, until son in law came on scene and sold the rig... to ME.
after a year of adding tiny amounts of coolant every month, we pulled the motor, dropped in LQ9. Runs great, just **** for heat.
so.... after that long tale of woe.....

Please recommend the best brand of radiator cooling system flush.
Also:

Best technique for effective flush/ de-scale ??

.. Thinking of pulling hoses, rinse out the antifreeze from JUST the heater core, then maybe pouring in a gallon of vinegar, let sit for a few days, then blow that out with airhose, and refill with best recommended parts store brand Cooling System Flush , maybe try to rig up a submersible pump in a bucket, couple hunks of garden hose and power flush nasty-*** chemicals through the heater core for 48 hours or so....

Am I overthinking this ?
.
Thanks, from
Cold Feet in Alaska
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Old Jul 25, 2025 | 04:36 PM
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What I've done is to disconnect the lines from the water pump and drain then with one of the hoses up as high as I could get it I'd fill the lines and the heater core with CLR and let it soak for about an hour then I hooked up compressed air to one of the lines and blew the lines out. This worked for me on my friends truck but if it's too rusted out it may start to leak and just needs to be replaced. I'd repeat a few times and it might just do the trick!
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Old Jul 26, 2025 | 10:03 AM
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Aluminum Heater Core isn't going to rust, running vinegar through it might be a problem with some corrosion tho. I'd look up what acetic acid will do to aluminum and if cleaning vinegar might be safer if it's a weaker solution.
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Old Jul 26, 2025 | 05:57 PM
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My buddy would always use just water in coolant system and when I cleared his heater core it was clogged from rust deposits. I know that their made of aluminum and when running an aluminum block you could probably get away with running water but I stressed to him that running water in an iron block should be avoided and if you live where you deal with freezing temperatures you can destroy an engine if the water freezes in it.
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Old Aug 1, 2025 | 01:59 PM
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I drained coolant, rinsed with fresh water, and poured in 2 quarts of Blue Devil radiator cooling system flush 4 days ago, had 3 heat cycles, and drove a few miles. Just water and Blue Devil. probably let it soak another day or two, then drain and refill with the PRESTONE clean n Flush, circulate that for a week.
The Prestone has Sodium Citrate .
.
Where ya supposed to get rid of drained coolant ?
Do I have to contract with ELON to remove it from the Environment > ?
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Old Aug 1, 2025 | 07:53 PM
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For a deep flush, Prestone or Thermocure is solid. Vinegar soak (1-2 days) in the heater core works, then power flush with a pump. Don’t overthink it just blast the crap out. Check the thermostat too. Stay warm.
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Old Aug 1, 2025 | 08:35 PM
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Every Heater Core I have flushed, I flush it backwards. Coolant is always flowing one way, so when back flowing is when the most amount of crud seems to come out.
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Old Aug 7, 2025 | 08:52 AM
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Originally Posted by Full Power
Winter rig maintenance time. 2004 chevy engine gets up to temp quick, but Cabin HEAT is very slow to come up... 20 minutes to get defrost.
Prior history is that original owner had CRACKED CAST-TEch head(s) on LM7 and used every brand of stop leak and engine block sealer on the market.... and THEN parked the vehicle for several years, until son in law came on scene and sold the rig... to ME.
after a year of adding tiny amounts of coolant every month, we pulled the motor, dropped in LQ9. Runs great, just **** for heat.
so.... after that long tale of woe.....

Please recommend the best brand of radiator cooling system flush.
Also:

Best technique for effective flush/ de-scale ??

.. Thinking of pulling hoses, rinse out the antifreeze from JUST the heater core, then maybe pouring in a gallon of vinegar, let sit for a few days, then blow that out with airhose, and refill with best recommended parts store brand Cooling System Flush , maybe try to rig up a submersible pump in a bucket, couple hunks of garden hose and power flush nasty-*** chemicals through the heater core for 48 hours or so....

Am I overthinking this ?
.
Thanks, from
Cold Feet in Alaska
Chrisfix on YouTube has a good video on heater core flushing, vinegar may be overkill a garden hose should do the trick
Reply
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