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96 Blazer overheating


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120k miles, 4.3 with the auto and 4wd.

 

Noticed I was loosing coolant and running hotter than normal, and I had no heat, pressure checked, found it was seeping though the intake gasket on the passenger side, I figured the no heat was due to the low coolant. So I pull everything apart, replace the gaskets, and reasseble. There is no bleeder valve for the coolant system that I can find, Haynes manual does not mention one. So I fill the engine up through the thermostat hole, put the thermostat in and then fill the radiator. First time out it overheats badly. Half mile of driving is at 230 and climbing. It started puking out of the radiator overflow. So I repressure check, and find there is a crack in the radiator. Replace the radiator, add coolant, throw in a new thermostat (one identicle to what came out, a 195deg 2 stage) let it burp itself for an hour and try to drive it. Overheats exactly the same, puking out the overflow, still no heat. Pulling the hoses off of the heater core, it seemed full. Jacked the front end way up in the air, to make sure the radiator cap was the highest point, and ran it, refilled, etc with no change in the overheating. The water pump has been replaced, and nothing is coming out of the weep hole.

 

The common thing I get is head gaskets, but I have no water in the oil, no steam out of the exhaust, and a great idle, which all say otherwise.

 

Any ideas on what to do next?

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check the hose that goes back into the radiator, squeeze it, if will be able to tell if it is flowing by squeezing it, you will feel it as you squeeze and feel it fill back up.

 

It sounds like pretty much everything is new, radiator, thermostat, water pump, also sounds like the head gasket is good. Maybe do a leak down test to check. Off the top of my head it sound like you have a blockage somewhere, or maybe your running really lean and it is making you overheat. Also, is there anything blocking the airflow of the radiator? sounds dumb to ask but you never know, is the AC condenser in front of the radiator like most cars? are most of the fins bent? may be blocking the airflow from the radiator.

 

Also, hate to be obvious, but are u sure your fluid is full, sounds like is, though whenever i fill mine, i leave the drain peacock on the radiator open until antifreeze comes out then close it, then i start the car and fill it untill the level stops dropping.

 

Also, do u feel any dragging on your drive line? might be a problem

 

bottom line, check fluid again, do a leak down test to test the oil, and check for blockages. little drunk... but i hope you get what i am saying

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you don't need water in the oil, good idle or steam in the exhaust to have bad head gaskets.

 

your heater core may be clogged, one hose (in) will be hot and the other hose (out) will be cold or warm. you may be able to clear it out by putting a water hose on the out side and flush it out.

 

there are a few things on the over heating part. fan clutch could have failed. the impeller on the water pump could have fallen off and not moving the water when your driving. there is more but its hard to say over the internet with out looking at it. you can pick up a block tester from NAPA and that will tell you if you could have bad head gaskets. it changed color with the presents of exhaust gas in the coolant.

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you don't need water in the oil, good idle or steam in the exhaust to have bad head gaskets.

 

your heater core may be clogged, one hose (in) will be hot and the other hose (out) will be cold or warm. you may be able to clear it out by putting a water hose on the out side and flush it out.

 

there are a few things on the over heating part. fan clutch could have failed. the impeller on the water pump could have fallen off and not moving the water when your driving. there is more but its hard to say over the internet with out looking at it. you can pick up a block tester from NAPA and that will tell you if you could have bad head gaskets. it changed color with the presents of exhaust gas in the coolant.

 

 

very true man... when i bought my car it had coolent running down the block and 90 psi number 3 cylinder... you could never tell by exhaust, power or anything... i know my head gasket is bad... only really way to know if ur gasket is bad is to tear down your engine... i know it sucks, but i am betting you have a blockage somewhere or not getting coolent flow...

 

also for cammaro aj... he said he juust replaced his water pump... i doubt it is fucked up.... but is a good guess also a bloockage to the heater core shouldn't affect the fact he is overheating. most heater cores are run in a parallel configuation, meaning the engine is still getting the coolent needed even if the heater core is getting none\

 

 

i know my spelling and shit is fucked up but i know i am pretty dead on... da,m beer

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Temp going in to the heater core is within 2-3 degrees of whats coming out.

 

could still be blocking most of the rows. i had a 96' vette in the shop a month or so ago that was hot in and out but when we put a clear hose on it to watch the flow there was hardly anything and someone just replaced the water pump on that too with a NAPA one. well needless to say we put another pump on and problem solved on the flow part and back flushing fixed the heat part.

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the impeller on the water pump could have fallen off and not moving the water when your driving.

 

Your good. I have never ever seen or even heard of this happening. Pulled the fan and belt off, spun the pulley and it spun really freely. Changed pumps and problem solved.

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