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Discussion Starter · #1 ·
L76 stock 6.0L, all aluminum radiator (no shoddy plastic)
So I mentioned in my alternator swap thread that I found a tiny amount of coolant on the belt after it had been sitting for a day. This prompted me to check the coolant levels and the dipstick in that yellow reservoir cap was completely dry. There was not a single drop of coolant on the dipstick from what I could tell. This led me to believe that there was no coolant in the reservoir/radiator.

I put about a gallon of 50/50 into the reservoir then noticed it was coming out of the overspill. I noticed that the coolant is above the top of the notches, and also noticed there's a temperature symbol. One question is how am I supposed to check the coolant cold? Is that impossible? Do I need to heat the car up first then check it? The thing is it was completely dry in the reservoir so even starting the car worried me. I don't want to heat it up to check the coolant level.

I'm wondering what happens if this level is too high? Do I need to drain some coolant out of the system? I did not fill directly into the radiator. I filled into the reservoir and a bunch of 50/50 came out of the overspill. Is it going to break something if I run the car with too much coolant in the reservoir? Again, not filled in the radiator it's in the reservoir

If I do need to drain, is there a drain plug of some kind? My radiator isn't stock it's an all aluminum one because the day after I bought the car the stock one cracked on that plastic piece (high side I believe) and spilled coolant all over the car on my way to work (shut off/pulled over immediately luckily no damage to the motor 40k miles later). But I believe if there's a drain plug on the stock one it'd probably be in the same location on this one since it's basically OEM replacement but all aluminum version.

Thanks!
 

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Not a single drop of coolant on the dipstick could equate to the level being too low to register. Shinning a flashlight into the reservoir may have helped to confirm or deny if it was indeed empty. Can check the coolant level at any time as long as the car is on flat ground. Bear in mind, Dexcool's natural orange color may make it more difficult to see where it registers on the "clear" plastic dipstick. Can remove the excess fluid through the fill neck or the radiator's drain on the. Too high of a fluid level won't allow for it to properly circulate throughout the system. Some excess fluid may escape through the seam where the neck meets the reservoir if isn't properly sealed. By the way, what brand is the radiator cap?
 

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No coolant in it when its cold could be from evaporation when it was hot.

Its an overflow for the expanding hot coolant and it will suck it back into the system if its needed

There is no problem topping it up as there is a vent hole if it gets too full when its hot.

Check the rad level when its cold and top it up if needed.
 

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Discussion Starter · #4 ·
Not a single drop of coolant on the dipstick could equate to the level being too low to register. Shinning a flashlight into the reservoir may have helped to confirm or deny if it was indeed empty. Can check the coolant level at any time as long as the car is on flat ground. Bear in mind, Dexcool's natural orange color may make it more difficult to see where it registers on the "clear" plastic dipstick. Can remove the excess fluid through the fill neck or the radiator's drain on the. Too high of a fluid level won't allow for it to properly circulate throughout the system. Some excess fluid may escape through the seam where the neck meets the reservoir if isn't properly sealed. By the way, what brand is the radiator cap?
I'm 100% certain there was no coolant on the dipstick. I know what color it is. It was bone dry. I could tell the difference after I filled it.

In terms of the radiator cap, I'm not sure what brand it is. There's no brand name on it. I just checked.
 

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Discussion Starter · #5 ·
No coolant in it when its cold could be from evaporation when it was hot.

Its an overflow for the expanding hot coolant and it will suck it back into the system if its needed

There is no problem topping it up as there is a vent hole if it gets too full when its hot.

Check the rad level when its cold and top it up if needed.
How high is the coolant supposed to be in the radiator when cold? approx? I don't see any level indicators inside of it.

And would filling both the radiator + reservoir be a problem at this point? Keep in mind the reservoir is overfilled now from what I can tell.
 

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The rad should be nearly to the bottom of the cap, really.

Overfilling the reservoir is not an issue as far as I know.
 

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For what's worth, may want to consider purchasing a genuine AcDelco radiator cap as aftermarkets could be problematic especially if they don't properly regulate coolant pressure.
 

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Hot or cold, the radiator is full all of the time. When the engine gets hot it pushes the expanding coolant and air into the overflow bottle. When it cools, it sucks back coolant to keep the rad full. As long as the overflow is filled above the bottom of the hose it’s fine and the system works. But of the overflow leaks or the water just evaporates. The if has to be topped up and that is where the dipstick helps. Only fill to the level on it.
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