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Thermostat brown.

revmaster

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Pulled off a thermostat . Was fairly new one. New Celsius coolant antifreeze made by Prestone. Thermostat is brown.

IMG_20250905_145837035.jpg
 
Looks like rust but a little mucky. . Did you flush the system before the new antifreeze?
 
Looks like rust but a little mucky. . Did you flush the system before the new antifreeze?
No. I was going to flush it. I took the water pump off . It's clean in the housing. I was checking the water pump .I'll reverse flush it. Using Celsius antifreeze. It's cheaper they say all garages use it. Antifreeze was a bit dirty but not bad. Looks clean coming out until it's in a pail then you see the dirt. . But color seemed ok..
 
That color of muck can also come from oil in the coolant. Double check those dipsticks for any foreign residue. I don't know what kind of antifreeze you used but in an old car that has had Ethelene glycol in it all it's life, that's what I would use. (the old green stuff)
 
No. I was going to flush it. I took the water pump off . It's clean in the housing. I was checking the water pump .I'll reverse flush it. Using Celsius antifreeze. It's cheaper they say all garages use it. Antifreeze was a bit dirty but not bad. Looks clean coming out until it's in a pail then you see the dirt. . But color seemed ok..
1. Celsius antifreeze is based on ethylene glycol (good)
2. Celsius is an “OAT” (organic acid technology) antifreeze similar to dexcool. I recommend that antifreeze.
3. Originally Mopars used an inorganic acid based antifreeze with silicates. There is a hard-to-find Peak antifreeze with a green label that is close to the original antifreeze…BUT, I recommend you use what you have.
4. That is 100% for sure rust. I suggest an acid-based flush (basic auto parts store radiator flush) with distilled water, drain and fill with more distilled water, drain and add 50/50 Celsius
5. Color means NOTHING…..unless it’s muddy brown, which means rust….but really, antifreeze color means zilch, nada, zip
 
X2 on the Thermocure. You MUST pull the block plugs on each side when you drain it, every cycle. I do this with both my small blocks and big blocks. They're a little tricky the first time. If they're square head, you must use an 8 point socket. The Thermocure needs a lot of flushing after. I ran it in the Charger for a weekend, then did 3 or 4 flush cycles.
 
Get some good cooling system flush and flush it however many times it takes to make the water run clean. Just use the garden hose during the flush cycles (no need to waste 10 gals of distilled water during flush) and then after it runs clean flush it out with distilled water to get the all the minerals out of the system. Removing the block plugs will make it flush faster during the cycles. Then fill her up with fresh antifreeze and distilled water. I use straight Prestone and mix it with distilled water, not the premixed stuff.
 
1. Celsius antifreeze is based on ethylene glycol (good)
2. Celsius is an “OAT” (organic acid technology) antifreeze similar to dexcool. I recommend that antifreeze.
3. Originally Mopars used an inorganic acid based antifreeze with silicates. There is a hard-to-find Peak antifreeze with a green label that is close to the original antifreeze…BUT, I recommend you use what you have.
4. That is 100% for sure rust. I suggest an acid-based flush (basic auto parts store radiator flush) with distilled water, drain and fill with more distilled water, drain and add 50/50 Celsius
5. Color means NOTHING…..unless it’s muddy brown, which means rust….but really, antifreeze color means zilch, nada, zip
Thank you for the info. Good to know. Id like to flush and clean and drain.it. but rad is new. I have Prestone radiator flush says to run from 10 min to 3 hrs depends on how much rust. Like to clean cooling ports . Prestone total cooling system cleaner..
 
Removing the block plugs allows the sediment in the cooling system to be flushed out. I’ve seen blocks so plugged with sediment that water barely drips out with the plugs removed. Use the commercial cooling system flush of your choosing. I normally add the flush and get the engine up operating temperature to circulate it through the cooling system. Then I’ll let it sit for 12-24 hours. Then I’ll drain the radiator, remove the thermostat and block plugs. I stick the garden hose in the water pump housing and flush with water until it runs clear. I use a long plastic tote to catch the water from the block drains to avoid rust stains on the driveway, but more importantly I can see when sediment is no longer coming out. I do the same with the radiator, it wouldn’t hurt to back flush the heater core while you’re at it.

Button everything back up and fill with your preferred type of coolant.

I would also recommend using coolant test strips annually to monitor your coolant’s condition. They are reasonably inexpensive…

 
Toss the Prestone flush aside and get the thermocure. Once you use it you will never use anything else. It is an excellent cooling system cleaner. Leaves it clean and no harsh chemicals to eat hoses or leave a chemical smell.
 
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