Question about 1990 GMC Rally

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Over heating i put new rad., new water pump and thermostat in my 1990 rally gmc and i still have problem with it over heating what could it be?

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I would guess a blown headgasket....check for a sweet radiator fluid smell from the exhaust pipe. this is bad news if it is. If the head gasket fails several things can develop. This gasket separates the oil jets...coolant jets and the top of the compression chamber from each other. when it fails..sometimes you lose a little compression...sometimes you leak oil...sometimes oil leaks into your combustion chamber (oil burns) or oil and coolant can leak into each other...(an oil slick in your coolant resevoir and or a milky residue on your oil cap from coolan mixing with your oil).If it has blown from the combustion chamber into your coolant, then when it draws in also sucks in some water..(thus the sweet smelling exhaust) then when the combustion starts then it also forces some of that explosion through that little leak-hole into your coolant system...causing excessive pressure...then also an air pocket forms from the exhaust. this repeats very often...then when you rev your engine suddenly you have a boil over... i hope this helps you...i hope its not a blown heasket...its around 600-1200 bucks to get it fixed depending on the car. there is a product on the market that might fix it by adding it to your radiator fluid...but i have heard very little REAL info on how good it works...i personally question all "Mechanics in a Bottle" type fixes

Posted on Mar 12, 2009


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