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Discussion Starter #1
So I've perused old threads on this topic - looks like no GTO's came with overflow bottles. what's the best idea folks have come up with? Just use a windshield washer bottle? that seems to be the consensus. My question being, will the radiator actually siphon coolant back in?

thanks Joe
 

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You can use a tall beer can, a washer bottle, or better still, you can buy a nice aluminum overflow bottle/tank from Jegs and the like. Yes, the coolant will syphon back into the system. Easy-Peasy.
 

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The washer jug is the most common/economical way to address this IF you have one to spare.
It's a MUST have on any of our cars that see track time but it's also nice to have a catch on any car with minor overheat issues.

However it's a band-Aid if your car is puking it's telling you something.

I'm always amazed at all the High Dollar cars that show up at a show/cruise,
then park and shut down and within minutes their prized possession is marking its turf ;)

Cheers
 

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Not sure why you need an overflow bottle, that's certainly your business, but at one time I also thought the same. I replaced the original radiator of my '71 GTO with a Cold Case one. Filled it. Drove it. Almost every time while sitting overnight, a sizable puddle of antifreeze appeared on the floor. Filled it again. Same thing. Thought I then needed an overflow bottle. But then I thought, this car didn't come from the factory with one, at least I don't think it did, so why this problem now?? I posted here and found my problem on this forum. Unbeknownst to me, the radiator was puking out extra antifreeze it didn't need or want. It was actually seeking it's own level of fill. So, once cooled, I removed the cap and saw that it was down about 1.5" or so from the top. Started the motor with the cap off and watched it. Eventually the thermostat opened and the radiator filled up quite quickly. Had to be quick with the cap. I never put anymore coolant in it and it never puked again. Runs at 180-185 all day long. Just sharing my personal experience, Nicholas.
 

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Like Nicholas I don’t run an overflow bottle. Nothing against them, but if the cooling system works good then the radiator is not supposed to be filled to the brim, rather an inch below the top. It then expands and contracts without spit out. It does have a spit out tube but mine never expels any, runs cool and I run it an inch below the top.

Like nickolas said if it seeks its level about there it should be okay. Now it does get hot the overflow saves you a modicum of antifreeze that would not have spit out, but the amount is only what your jar can hold, maybe a quart.

Newer cars have a little different design and the radiator is meant to be filled to the brim and then all filling goes thru the overflow can.

We drove many cars back then without overflow cans, but there is nothing wrong with running one.
 

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Discussion Starter #6
thanks everyone - after my resto project, I think I'll remove the washer fluid bottle that has been there for years (came with it when purchased 20yr ago). I also have kept my radiator at about 2 in down. It has very clear markings: (full-cold and full-hot) Neither of them are at the neck!

Appreciate the comments though - validates my own thoughts.
 
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