Overheating

1989 GMC C1500
6,000 MILES
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JONATHAN57818
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I put a 16 pound cap for my radiator on my 1989 GMC Sierra 5.7l and it began to overheat and leak antifreeze from the cap. Why is this happening should I put a higher psi cap or lower???
Jan 26, 2016 at 7:46 PM
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JOHNNYT73
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Have you replaced the cap? if not then it sounds to me as if the seal is bad and or it is not working and allowing the coolant to boil.
Jan 27, 2016 at 6:34 AM
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HMAC300
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could be a bad head gasket as well if it overheats.. putting compression into coolant.
Jan 27, 2016 at 6:37 AM
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JONATHAN57818
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I replaced the cap and put an new 18 pound. It still heats up to 230 and it returns to 190 but doesn't spill or seem to be overheating. I'm just wondering why the 16 pound didn't work?
Jan 27, 2016 at 10:31 AM
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JOHNNYT73
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Was the 16 psi cap the original? I would check your thermostat as well. Plus make sure you are bleeding the cooling system and getting all the air out of the system.
Jan 27, 2016 at 10:33 AM
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JONATHAN57818
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The 16 psi was new and my thermostat Is also new and how would I know if air is problem?
Jan 27, 2016 at 11:48 AM
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JOHNNYT73
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If you are overheating with no leaks, and you didn't on purpose try to burp the air out of the system. Did you bleed the system after replacing the thermostat?
Jan 27, 2016 at 11:57 AM