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Discussion Starter · #1 ·
Hello guys I just got my hands on a early Chevy trailblazer with a 4.2 straight six cylinder and I noticed my temperature was only running 180 degrees and it should have been around 200 or so and I am thinking either my temperature sending unit is bad or the thermostat is stuck open. It was only mid 50's today but it should still have been running warmer then that. My question is what must I do to get rid of all that dexcool crap and run straight old green antifreeze?

I know this sounds like a dumb question but can a regular garage do that sort of a deal or what would I have to do in order to do it myself and what would all I need? I just read you can't add them together.

Thanks guys for any help
 

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Replace thermostat, drain radiator, drain block, fill with straight water, go for test drive, drain everything again, fill to top of radiator and about 1/4 full in overflow tank with 50/50 Anti Freeze from Walmart or whatever. Test drive, let cool, check level in overflow tank, fill to cold level in overflow tank. Done. Just did my 2006 Trailblazer with same engine. Around here you can't get the old green anti-freeze anymore. Just use a decent quality 50/50.
 

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Discussion Starter · #3 ·
Well I do use 50/50 premixed green stuff and not the straight green antifreeze. I hate to ask but how did you get it to drain from the block completely? I am used to first gen old school small block chevy motors and not these more modern ones and I would not have a clue where the drain plugs would be on the block or where to look for them. That sounds like a good plan and when you used water did you use distilled water or just tap water since you was going to drain it quickly anyways?

Thank you so much for your input and just out of curiosity did you ever have the problem where you temperature gauge would only read about 180 degrees and not go any higher? Only just got my trailblazer today so I am new to some of its things but had a previous 4.3 older v6 Envoy years back and it always ran about 200 degrees and mine should be running that as its running to cold. Also how much gallons did your trailblazer hold?
 

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Yes I had the same problem with engine running too cold. Thermostat was bad. On these engines the thermostat and water neck are one unit. Click below and get a 192 Degree thermostat. Drain radiator and block by disconnecting lower radiator hose at radiator. Flush with tap water 1 or 2 times or until water runs out clear. Never put cold water into a hot engine to avoid block or cyl head cracking.

 

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Unless you totally drain the block which involves removing the screw in plugs in the bottom of the jackets close by the engine mounts you shouldn’t change the type of antifreeze.

Once open the engine cooling system and the heater core needs to be flushed with clear water. Then new type antifreeze can be introduced. It’s a lot of messy work.

New antifreeze should be either a commercial 50/50 premix or you can make your own from straight green and either deionized or distilled water. Tap water contains too many reactive dissolved minerals where typical well water is rich in lime, iron and sulfates that occur naturally where “city” water not only may include these natural dissolved elements but also carries chlorides used as a disinfectant and maybe fluorides if the water district feels its their responsibility to prevent tooth decay. All of this stuff results in a corrosion products in your coolant that are especially brutal on the aluminum parts that the coolant touches.

Frankly the temperature at 180 is just fine more likely than not a previous owner decided to rid the engine of the typical 190 to 210 thermostat GM installs. The higher operating temp in theory at least improves milage this being more something engineers can dink with in a dyno cell than something you’ll experience on the street. If you’re building a high compression engine with aluminum head’s it becomes a playground for oozing out more power without hitting the fuel‘s detonation limit, but this is strictly a hotrodding game with Ricardo combustion chambers and preferably aluminum heads.

Bogie
 

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I pull the radiatior
Remove the thermostat
Grab a garden hose and just fill it through the top hose
I let that go for 10 or so minutes
Then pull the thermostat hoses at the engine or shutoff valve (if equiped) and reverse flow the heater core.
I then reverse flow the radiatior for 10 minutes.
Reverse flow your overflow

Put everything back together with a new thermostat and fill it up to the top using that upper hose with water from the hose.

Take a "mean" 5 to 10 mile drive somewhere like a store etc before parking it for 10 minutes at the location then drive it back mean.

Let it cool for a hour+ then drain the water out by pulling the radiatior, lower hose and heater core hoses.

Fill it back up with 50/50 green mix and your good
 

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When I was an auto tech I changed a lot of plastic intake gaskets that dexcool ate away. We always changed over to the classic green antifreeze. Pull the radiator hoses and let every thing drain, than use a garden hose to flush everything out until you can’t see any antifreeze. Using lighter air pressure blow in all the lines you can to flush the water out. Find out how much coolant system your holds and what mix ratio you want to use 50/50..60/40 ect. If you are going with 50/50 Divide your full capacity by 2 and pour that amount of straight antifreeze in your cooling system and fill the rest with water. Since you will never get all the water out of the block this will ensure your mix is right or very close to right.
 

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Oh one last thing. Get some bright green spray paint and spray your cap(remove it or tape off the area around it first).
Then to further idiot proof it write GREEN ONLY on your overflow.

The rare cases I get my oil changed at a oil change place(winter usually) I tell them to only do a oil change. Do not touch the coolant or anything else.

Because yea mixing dex and green is bad.
 

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I agree... change to green. I'll be doing that in the Express Van I recently picked up.

There is a reason GM has something like 41 lawsuits against Havoline for that crap. Dexcool is wonderful stuff until it isn't, and the only thing it takes to make it go sour is air or silicates (which your water jackets are full of from the casting process)
 

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Discussion Starter · #10 ·
I usually take my vehicles to get the oil changed but I am always careful on what they do and always give them instructions on if I don't want a certain thing done. The place I go to only tops off oil of course and washer fluid and that is it. I am also careful to where I go as I don't like some guy stripping my drain plug on my oil pan and even to this day the shop I go to I only let certain folks work on my vehicles as they are guys I used to work with and I know there practices.

I plan on getting a new thermostat housing unit and watched some videos on youtube so I know what is involved on that part and will get it done here soon. I plan on using 50/50 strength like I do all my vehicles and its the old stuff. I am going to try and see what the radiator looks like and if I see to where it has any gummed up junk inside I might replace it as well just to keep things flowing good. I have seen a Preston flush system being used before and what is your opinions on that? I know it will vary. I watched a few videos on folks who flushed out Dexcool and they measured the amount they drained and kept adding Distilled water only and ran it for 7 minutes with the heater on and then flushed it over and over again till it was as clear as it could be. Then they added full strength antifreeze at half of what it holds and put the rest of Distilled water in to make it a 50/50 mix.

According to what I have seen my Trailblazer holds 3 gallons or about 13 quarts with the overflow included. I am afraid of using air as my tiny air compressor goes up to 90 psi though it runs out of pressure really fast though as its just something that is for like bicycle tires and carb cleaning type of a thing. I think Cerials idea sounds the easiest and I don't care how messy I have to get as if it gets rid of that nasty Orange junk then I am up to get it done. I got the thing with only 109,000 miles on it and besides some suspension parts needing placed and tires it was a good buy and the previous owner only drove it mainly on a farm and was an older lady and it was not used much during its entire time.

I just want to get the cooling system as clean as possible. I have not yet tried to see where the block plugs are located and I am assuming one on each side toward the bottom. I know not to add any water and drain it while its hot as it would crack it. I don't know the flow direction though as I am used to small block chevy old school motors. I am trying to find a flow diagram for the 4.2 but all I can come up with is the 4.3 previous v6 they used to use.

Thanks guys for all your help. I am going to get a new thermostat unit which most likely is the original and time for a new one anyways since I doubt it was ever replaced before.
 
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