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Old 02-04-2019, 10:06 AM   #1
Mr_Rich
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Radiator/ cooling system flush

I have my '89 K1500 EC parked in the driveway getting much needed cooling system maintenance. I've let it go for the last five years since I installed this engine and it's finally caught up with me. I literally had rust flakes clogging the cooling system like red kitty litter; no kidding. It lined the upper radiator hose and when I squeezed the hose it "crunched". Don't ever let your cooling system get this bad. Phew. Once the storm is over I plan to pull the radiator and flush it very well to get any remaining residue out. I've flushed the block and heater core already and another plan of attack is to replace a leaking freeze plug in the block behind the alt./ PS pump. My thoughts are to use Dexcool since this is the coolant I have on hand since two of my other vehicles use it. Thoughts? I know some people don't like the stuff but I don't have a problem using it in my newer vehicles.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 02-05-2019, 08:07 AM   #2
Palf70Step
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Re: Radiator/ cooling system flush

I flush and NEVER return to dexcool. Too many headaches associated with it. Just my opinion.
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Old 02-05-2019, 09:36 AM   #3
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5 years is too short a time to have damage like that.....

First to have problems like your describing in a 5 year time span had to be either a poor quality (used) engine to begin with or you didn't use any type of coolant that gave corrosion protection.

I deal with vehicles on a regular basis that used Dex and mine originally came with it. I wouldn't be caught dead using it. If you can't afford propylene glycol, then use the typical ethylene glycol.

Did you know that several GM vehicles had Dex powder in the cooling system when delivered to the dealers. As these same vehicles aged, they produced a sludge that looked like play sand? Funny how I routinely see issues with Dex that I never see with good ole green.

Don't make the mistake of cutting 100% with tap water. Only cut it with distilled water or buy 50/50. Minerals in tap water cause "bloom".
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Old 02-05-2019, 09:55 AM   #4
hatzie
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Re: Radiator/ cooling system flush

Flush with a Chemical
  1. Rinse the engine out from the bottom radiator hose with the thermostat removed til the water runs clear out the top hose then remove and rinse the radiator the same way.
  2. Re-install the radiator and thermostat then fill with tap water and run the engine til it's at operating temp. Let cool and drain.
  3. Rinse out again til the water runs clear.
  4. Repeat step 2 & 3 til the water is clean and clear at operating temp.
  5. Replace any dodgy looking, super hard, or soft hoses.
  6. Get some Wynns' Heavy Duty Professional flush and follow the instructions to clear out the rust and scale.
  7. Repeat steps 2 & 3 again til the water is clean and clear at operating temp then continue with the next step after this one.
  8. Carefully look over the water pump, Radiator, and Heater (pay attention to the smell with the heat on). They may leak after the scale is removed because you are exposing holes that were covered by the rust and scale. If you had questionable intake gaskets or leaking head gaskets that were band-aided with Bars-Leak or the leaks were just blocked by crud and rust they will rear their ugly heads now or soon.
  9. If there are no leaks let cool and empty the system.
  10. Replace the thermostat.
  11. Look over all your hoses again and make sure they are all in good shape.
  12. Re-Fill with 50:50 Prestone Dexcool. Dexcool works just fine and 50:50 means you don't have to find distilled water to mix it. The problematic early formulations are long gone. It'll precipitate silicates if you mix it with the old green silicate anti-freeze or if you have a leaky head gasket or cracks in the heads or block... the green silicate stuff will make acids and do nasty stuff with a bad head gasket or cracks into the combustion chamber too... that's a symptom not a causal factor. The coolant has nothing to do with intake and head gaskets failing it's just a convenient scapegoat. Those failures are blamed on both Dexcool and the old green silicate stuff. If the gasket failures have anything to do with coolant I'd bet it's that said coolant was mixed with TAP WATER instead of Distilled. Tap Water in engine coolant is a BIG NO NO. If you decide to use Silicate antifreeze then buy the 50:50 pre-mix and mark the reservoir so you don't mix it with Dexcool. Both of them work. Neither is better.

I usually replace the serpentine belt and look over the tensioner and idler pulleys. I replace them if they feel crunchy or look less than 100% but that's personal preference. If the idler bearings or the tensioner arm feel crunchy you'll be back in there soon. Might's well do it now.
Look over the clutch fan as well. A rule of thumb is mark one fan blade and spin the clutch fan hard when the engine has not been started for 24hours. If it spins more than 5 rotations the clutch is likely worn out.
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Last edited by hatzie; 02-05-2019 at 10:21 AM.
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Old 02-05-2019, 02:19 PM   #5
Mr_Rich
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Re: Radiator/ cooling system flush

This engine that I installed back in the '12/'13 time frame I actually stored for over twenty years (!!) in my garage planning on using it for my retirement car project. It was a low mile engine at the time and still had clean cast iron surfaces before any varnish formed. I turned it over every now and then by the crank bolt over the years before I decided to use it in my truck. One of the mistakes I made was not totally draining the block and flushing it at the time I installed it. One of the freeze plugs at the back of the engine leaked and I also had a bad rebuild of my original 700R4. I took care of both problems in the following months.
I have a leaking freeze plug behind the alt./ PS pump and I plan to take care of that as soon as the storm ends. I plan to pull the radiator and flush it separately so I'm not just recirculating any deposits or debris in the system with a flush.
This has been kind of a deceptive situation since I try to keep my engine compartment clean, and these are the things that happen unseen.
I always use distilled water in the cooling systems of my vehicles.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E

Last edited by Mr_Rich; 02-05-2019 at 02:22 PM. Reason: ...distilled water
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Old 02-05-2019, 02:59 PM   #6
hatzie
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Re: Radiator/ cooling system flush

I didn't know the whole situation. Just trying to be thorough and not leave anything out.

You may end up replacing several freeze plugs since it sat with coolant in it. I would not assume there's not a bunch of rust inside the block behind the freeze plugs at this point. Voice of experience.

Heat adds energy to the chemical reaction that accelerates the action of the caustic cleaning chemicals on rust and calcium/silica scale deposits. You can do the radiator cold but it will likely not work as well as circulating it through the cooling system for 15 or 20 minutes at 195F. It also won't clear out the heater core and other hoses.

A brandy new radiator is right around $100. Aluminum will pit pretty badly under calcium scale. If it's too nasty inside it'll probably leak as soon as you remove the scale. It may be just as well to use it as a sacrificial part when you do the caustic flush and replace it with the new radiator when the rest of your cooling system is fresh and clean.
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1959 M35A2 LDT465-1D
1967 Dodge W200 B383, NP420/NP201
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 02-05-2019 at 03:17 PM.
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Old 02-05-2019, 03:40 PM   #7
Mr_Rich
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Re: Radiator/ cooling system flush

I appreciate everyone's comments. I'm on a very limited budget so I'm trying to use what I have on hand. I'm mainly trying to get rid of the remnants of the red "kitty litter" that caked the upper rad. hose and clogged the heater core. I flushed those out pretty well but I want to take care of anything that's left so pulling the radiator is part of that plan.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 02-05-2019, 10:03 PM   #8
ChevyTech
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Re: Radiator/ cooling system flush

I agree with other people posting.

I would not put Dexcool in it.

When I flush one of my vehicles I NEVER put Dexcool back in them.
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Old 02-06-2019, 11:53 AM   #9
speedygonzales
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Re: Radiator/ cooling system flush

First identify if the kitty litter as you put it is chemical sludge or actual metal using a magnet.

Dex (not sure what you had in it to begin with) can not be mixed with additives or green coolant. Sludge is the result. Dex was designed for Aluminum engines.

If the level of Dex is allowed to go low, SLUDGE is also the result

If it turns out you have/had metal corrosion (as you described) you got a lot of work ahead of you. If you want to maintain this engine for any length of time.

https://www.getahelmet.com/jeeps/maint/dexcool/

http://www.sancarlosradiator.com/electrolysis.htm

https://www.cartechbooks.com/techtips/antifreeze

http://www.luisa.com.gt/sites/defaul...x_dex_cool.pdf

In the second article you will see this:
"Fact #5 If you want to prevent electrolysis from taking hold, the time proven flush and fill is all that is needed, as long it done before coolant decomposition begins. However, once electrolysis has taken hold, a simple flush and fill just isn't enough, and more drastic measures are called for.

How do we get rid of electrolysis? Since automotive electrolysis is a chemical problem as mentioned above, the answer to ridding ourselves of this problem will be to neutralize the acid. In addition we need to remove the spent antifreeze, remove any metal particles in the deep reaches of the engine block, and "scrub" the internal surfaces of the block. Sound like a flush to me. But not just any flush. We need to REALLY flush this thing out. We first pull the thermostat out, connect our flush machine4 and let run. Sometimes we flush for as long as 36 hours. Once the flushing and rinsing is complete, new antifreeze and fresh water (50/50 mix) is installed with a new thermostat. Generally distilled water is not used, as it tends to be "hungry water" looking for ions. A chemical additive is then added to help in a variety of ways. It will control pH, help the coolant to remain non conductive, and contains an oxygen scavenger to prevent cavitations, erosions, and pitting. Last but not least, a sacrificial anode is introduced into the cooling system to "pull" any stray electrolysis away from aluminum components. Don't forget to retest for voltage in your cooling system. If you have more than .1v (one tenth), your not done flushing! "

Notice that since it requires additives, DEX could not be used.

Do what you want with this information, you been warned.
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Old 02-06-2019, 01:40 PM   #10
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Re: Radiator/ cooling system flush

Okay. Got it. No DEX. Five years ago I replaced the idlers, etc., so that is not a concern. Main issue right now is that freeze plug and then I'll go from there. Thanks!
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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