Did a 75k mile Coolant Flush

FL335i · January 21, 2018

As stated, I did a coolant flush at 75k on my '14. Few lessons being the first time doing this on the newer K2XX trucks.

1- The owners manual states 5yrs or 150k, whichever occurs first for a coolant change. I'm at 75.5k and 41 months. Even that was too long of an interval. I've been running an external coolant filter which I change the filter every year, but even so, the one compartment of the coolant bottle toward the back of the truck, had crusty 'stuff' built up on the walls. I took the tank out and hose it out beyond belief but could not get it 100% clean. The tank overall had a film on the inside. Similar to algae on the inside of a fish tank that needs cleaning. I bought a new ACDelco tank last night online. Moral of the story here is the overflow tank probably needs removed and hosed out probably every 12 - 18 months to keep this build-up at bay. 5yrs/150k my arse. The barnacle like crap was at the liquid level line. The algae layer was throughout. Hosing the tank out cleaned the algae film but the barnacles would not come out. Plus the one compartment you cannot hose out. It's a baffled compartment. Hence the new tank.

2- Even though I check the coolant for electrolysis at every oil change, it doesn't mean much with dexcool from what I have seen. That is not a good indicator of it's performance. My truck's coolant even up to yesterday before the change showed almost no electrolysis voltage at all; literally 0.03V. I have the same coolant kit on both my '14 and my '89 K5 Jimmy. I change both filters at the same interval, 1yr. On my K5 it works like a champ. Cleaning up the system, picking up debris etc. But that truck is running Prestone Green, not dexcrap. And the underside of the coolant filter base is clean as a whistle in the K5. Yesterday I noticed while taking the coolant filter off my '14, the underside of the filter base was heavily corroded. To the point where I removed my coolant filter system from my '14 due to the heavy corrosion of the coolant filter base. The filter base is carbon steel. I painted the exterior of them flat black, but obviously the inside portion where the filter mattes to it is uncoated steel. Again, the K5's is clean steel 2yrs in the making. The 14's looked horrific. So rather than buying a $27 coolant filter every year for my '14 I will put that money toward doing coolant flushes more frequently. But the point here is the DexCool was so weak in the anti-corrosion department the filter base steel corroded to S**T. So that's all the proof I need for 5yr 150k mile coolant.

3- The radiator drain plug is very accessible on the passenger side, under the lower hose so you do not have to remove the lower hose like on other vehicles. What I did learn is you have to remove both heater core hose from the block on the front right part of the engine. This is the only way to remove the water from the block. Also remove the coolant tank as the rear-ward compartment will not drain. I even removed the 1" hose from the coolant tank, that compartment still holds water. So remove the tank and drain all the water out of it and remove the heater hoses from the block. THEN I used a 6HP shop-vac to suck the water out of the block from both heater connections at the block. I shopvaced everything out. Block, coolant 1" supply hose, you name it. I pulled about 2-3 gallons of water out of the system by doing that. The radiator only will drain about 1-1.5 gallons.

4- For flushing, I put the garden hose in the overflow tank for clean water supply. Remove the radiator drain plug completely. The Tstat overflow 5/16" gets disconnected from the coolant tank and dumps on the ground. Turn the hose on just enough to keep the water level stable in the tank. Run the truck to get it up to operating temp and make the T-stat open. Turn heater on, fan on low speed. I ran the truck for about 20 minutes like this with some 2,500rpm runs to help warm it up and push water through the system.

5- See Item # 3 for ensuring the system is evacuated and you've removed all the water. Then fill with 50/50 Prestone Dexcool. I buy it at walmart for $12/gal vs $20/Gal ACDelco stuff online. After seeing the terrible performance the factory coolant did protecting the coolant filter base steel, I see no reason to buy the ACDelco coolant. Prestone has never performed bad for me. So moving forward I will be removing the coolant tank and hosing it out to prevent barnacles. The complete flush and fill will go no longer than 3yrs/36k as with green stuff recommended intervals. Lesson learned.

Edited January 21, 2018 by FL335i

diyer2 · January 21, 2018

Thanks for the info.

Classic example of why I belong to this forum.

KARNUT · January 21, 2018

Reminds me of the 04 Z71 I had. I waited the recommended time for coolant change, 150K for me was two years. About 2wks later the water pump went out. My system was full of crud that probably broke free from the new fluid. I figured I was safe because I did mostly HWY miles.

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Donstar · January 21, 2018

Good information. I'm certain a service department tech wouldn't go to the efforts to give a thorough flush and clean such as you describe. This makes it even more important to do this regularly. I am sure it comes to a surprise to some how crud can accumulate in such a closed system. Here is a home remedy that will help convince you: If you're not in the habit of draining a few gallons of water out of your home hot water tank every couple of months, drain a bowl of water from the tap located at the bottom of your tank. You may be in for a bit of a shock!

FL335i · January 21, 2018

Donstar- I hook the hose my house's hot water heater once per year and flush it out. Tons of sediment. but that's not a closed system as it's supplied by miles of pipe from the water plant. And you are correct, i'm sure a service dept would not go through the efforts to flush and evacuate the system like I did. They would probably pull the drain plug and re-fill.

Donstar · January 21, 2018

I knew "closed system" was not the best term and I know the analogy was a stretch for those that are "in the know". I remember in my youth working for my father in his plumbing and heating business. Customers were often bewildered by the amount of sludge being stored in their tank. In those days much of it was attributed to the corrosion of the galvanized piping within the house. I imagine the build up in an engine's coolant system is from an internal corrosion type activity.

Colossus · January 21, 2018

That's why I keep telling people to not go off of how things look, including spark plugs and fluids. "Oh but my spark plug still looks practically new and is still gapped just fine at 100,000 miles!!" HA!

I take my truck to a shop that uses one of these to do the coolant flush. There are other tools out there that do a good job, but I am sold on this one.

https://www.youtube.com/watch?v=DJ_F8GBRvEU

KARNUT · January 21, 2018

Spark plugs are a different story. On that same 04 Z71 at 100K is the recommended change. I ask a auto shop owner friend about changing them. He said run them till the check engine light comes on. At 180K I traded the truck in with original plugs running great.

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Retired Bob · January 21, 2018

Here's a video on how the service tech should be flushing the coolant system for a 2014 + Silverado:

https://chevroletforum.com/how-tos/a/chevrolet-silverado-2014-present-how-to-flush-your-radiator-389865

Maybe not as thorough as FL335i, but ......

How often to do a flush and what brand coolant is another matter. Some even suggest using distilled water for the cleaning flushes.

FL335i · January 22, 2018

As for the interval.... The key while reading the manual is the 5yrs. If they are saying 5yrs... it's more like 3yrs/50k. or 3yrs 60k. I'm probably going to do the 3yrs or 50k whichever comes first.

mookdoc6 · January 22, 2018

Great Post! I just did mine at almost 50K.......For many reasons FL335i mentioned.....I remember when it was only 1 color and it never went past 36K...So that is what I always did on every vehicle.

Things change and before you know it Brake fluid is in manuals every 3 years or 36-48K? And during that time Coolant has gone from 36K to 150K? WTF, Really complete nonsense you all know how fast aluminum corrodes with proper acidic surroundings? Anyway, well this is my first vehicle in many years I did not change fluid myself. I looked at it thought crap I disconnect the bottom hose and deal with all that fluid gushing out and then what do I do with it? Glad to hear there is a pet-cock I didn't look hard enough I guess....

Back to the Flush....... nonsense if you take this Crap to 150K boys absolute hogwash! I watched my temperature loose 10F cooling from the second I drove off lot to now which is not even 2years.....Yes, First thing I do is write down all Dash values on brand new vehicle at FULL operating temperatures..... then I remove that stupid question in my head of well I think it was always reading this and now it reads this?

I have one mantra in life and that is Coolant is ALWAYS replaced 50K your vehicles problems will most always be reduced....I have owned many vehicles and Water pumps are something I don't replace I my vehicles and if you do on yours it's coolant related and I will bet you will be changing it again if you hold vehicle long enough as that scenario plays out over and over.

108.00 Bucks was my total out the door after taxes for a complete flush and fill....No mess, no fuss best of all I didn't even bird dog the tech because if I did I would have had issues best I don't know what the hell he did? So F your stupid brake fluid for 150K is how much I care about that shit but DEXCOOL to 150K your F'n kidding me....please on it's way out at 75K and shot after 100K,,

Eddie 70 · January 22, 2018

I read this thread last night and thought I should get after mine and flush it this spring. Fast forward to this morning. I am backing in my spot and I notice steam coming from the front of my truck. Its dark out but I pop the hood anyway. I cannot see the leak but can smell it. Hopefully the extended warranty will cover the fix. The coolant level in the bottle is down about 1/2" to 3/4". Calling the dealer today to get it setup.

mookdoc6 · January 22, 2018

46 minutes ago, Eddie 70 said:

I read this thread last night and thought I should get after mine and flush it this spring. Fast forward to this morning. I am backing in my spot and I notice steam coming from the front of my truck. Its dark out but I pop the hood anyway. I cannot see the leak but can smell it. Hopefully the extended warranty will cover the fix. The coolant level in the bottle is down about 1/2" to 3/4". Calling the dealer today to get it setup.

Sucks! I thought that kind of luck only happened to me.....If you have the older 14 model I believe they know it's a known issue and will take care of it so press for it and let us know the outcome. Thanks, Mook

Eddie 70 · January 27, 2018

Just to update my previous post about the leak. I took the truck to the dealer today and they replaced the radiator and installed a the revised thermostat and rented me a car for the 3 hours I was with out my truck. I have 96500 miles on the truck and glad it started leaking when it did. The service guy I usually use, Austin, was not at his station today when I got there. A new guy, Robert, was in his station. I talked with Austin when I called about setting up an appointment. I was informed by Robert that Austin had gotten a promotion and was now over the Service Department. Austin was the only reason I was using this service department. Hopefully as the boss, Austin will do as well. He got me to come back several times. BTW, Robert renting me a car to use for 3 hours was an awesome extra.