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Old 05-11-2016, 08:42 PM   #1
1970 C10 MJW
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Coolant overflow

So when my truck gets up to temp and driven for a while the radiator will have lost a decent amount of coolant once cooled. Obviously I need an overflow... is anyone using the factory radiator and cap with an overflow that seems to be functioning? I don't want to replace the radiator right now it's only 3 years old thanks in advance guys
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Old 05-11-2016, 10:17 PM   #2
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Re: Coolant overflow

Are you loosing water out overflow tube or into engine? Probably not your radiator..have you changed the cap?
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Old 05-11-2016, 10:41 PM   #3
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Re: Coolant overflow

You don't necessarily need an over flow bottle. The full mark on a radiator without an overflow is several inches down from the cap, so if you fill it all the way to the top, it will puke out what it cant hold, after that it should be fine if it isn't overheating.
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Old 05-12-2016, 11:33 AM   #4
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Re: Coolant overflow

Quote:
Originally Posted by mongocanfly View Post
are you loosing water out overflow tube or into engine? Probably not your radiator..have you changed the cap?
............... X 2 !
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Old 05-12-2016, 09:40 PM   #5
1970 C10 MJW
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Re: Coolant overflow

I have changed the cap. Are there higher pressure caps available?
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Old 05-13-2016, 12:21 AM   #6
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Re: Coolant overflow

I have a 25lb cap on mine..
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Old 05-13-2016, 12:49 AM   #7
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Re: Coolant overflow

I've always run a 16lb I believe.
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Old 05-13-2016, 08:35 AM   #8
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Re: Coolant overflow

I use a 7# cap and 50 50 anti freeze with a catch can
I run a electric fan and A/C
Are you sure you do not have any air trapped in your system
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Old 05-13-2016, 02:06 PM   #9
1970 C10 MJW
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Re: Coolant overflow

Engine has about 15-20 hours on it so I would think that the air bubbles would be gone. Where do you get a higher pressure cap
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Old 05-13-2016, 03:12 PM   #10
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Thumbs up Re: Coolant overflow

Just for the sake of doing our part for the environment put a over flow on it. They are cheap enough and it will save you money in the long run. Just take the hose that it runs out of now and hook it to the over flow.
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Old 05-13-2016, 04:02 PM   #11
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Re: Coolant overflow

The air pockets solidaxle is talking about is in the engine..did you fill the engine through the top radiator hose until full? This will eliminate most of the air that's trapped..if you've ran it that long without it overheating I don't think you've got that problem..if its got air trapped it will immediately run hot and the thermostat doesn't open. Radiator caps are sold by parts stores everyday..from my research when doing my swap I found they recommend less than 20lb for older style engines and over 20lb for newer ls engines..doesn't mean a lower than 20lb won't work its got more to do with how much pressure your system can stand without problems and they also said get the biggest one you can find..my old 350 already had the 25lb on it so I just left it on. Like andy suggested get you a overflow tank..that way any coolant that goes out the overflow due to high pressure will be pulled back in when it cools off and the pressure drops...in theory..
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