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Question about 1985 Nissan 300ZX

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I own a 1985 300zx Turbo?.I like to know why my

I own a 1985 300zx Turbo with 51,000 original miles….I like to know why my overflow tank doesn’t return coolant to my radiator after cool down. I usually have to put a quart of water/coolant in my radiator every couple of days while my overflow tank becomes fuller.

Thank you, James White

Posted by whitej2000 on

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Your overflow tank works on suction to return coolant to the radiator. Check the line and nipple ends for any cracking (cracking on the plastic radiator nippl is very commom). The radiator nipple is not under high prrssure like the fluid under the cap (inside the coolant system). It's on the otherside of the cap and will never "stream or gush" coolant (uless you are over heating badly). As the coolant in the radiator cools it creates a vacuum and draws coolant back from the overflow throgh a small hose. You might not see any leaks as coolant heats up and travels to the overflow. It might be a very small leak and you are usaully driving around and drying up before you see it. Even with a very small crack it will only draw in air and not liquid (as liquid is way heavier than air). Also, I've seen where people have taken out (or fallen out) the tube attached to the overflow cap that goes down deep into the overflow tank. That tube should be long enough to almost reach the bottom of the tank. It's hard to know if something is missing if you do not know it was suppose to be there in th first place but it needs to be there.

Posted on Jul 23, 2010

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Change radiator cap, it's not holding the pressure right

Posted on Jul 04, 2010

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