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Discussion Starter #1
ok hi there. im not new to the chevy brand, just the impala. well anyway, i just picked up a 2002 base impala with a 3.4 and 169k that supposedly had a bad head gasket. i only paid 200 bucks for it and the body is in great shape. deffinately a steal. btw pics are in my garage. onto the problem.

so i was driving it home last night and was cruising along and it overheated once and i pulled over for about 15 to 20 minutes. let it cool down. then took off again now when i was driving the temp gauge went past half like it was gonna overheat then i hear a click and the defrost heats up and the temp drops below half to about 1/4 or so.

now today i popped the hood checked the oil and coolant, both looked and smelt like they should, oil and coolant. i thought that if it was a headgasket one or both would be milky from mixing. so i drove it about 20 miles and fine then on the way back the temp gauge starts to go to the overheating. i drove it home, just a few blocks from where i was, and pop open the hood and stick my hand on top of the intake and it was barely warm. shouldnt this be hot if its truly overheating. well thanks for any help in advance and i hope to learn a lot from this forum
 

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Have your mechanic do a compression test on this engine. Then intake that you put your hand on does not have coolant passages for it was the Upper Intake. The Lower Intake has coolant hoses that hook up just below the TB, and it should have been warm.

Your gasket may be cracked between cylinders, or just at an Intake Port, or even an Exhaust Port and not cause the oil and water to mix or leak. Or it could be cracked where it only blows into the water jacket and out the coolant resevoir.

With out seeing the car and evaluating it, it is hard to tell you exactly what the problem is. For it could be that the electric fans are not working, water pump is weak.

Hope this helps.
 

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Also have the mechanic use a heat gun to determine engine temp when the gauge shows its getting hot, these cars have problems with the gauges that read incorrectly.
 

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Discussion Starter #4
i am doubtful of the headgasket diagnosis. i work with the guy i bought it from, and he is deffinately a little scatterbrained. he admits that he knows nothing about cars. i know the guy doesnt have much extra money so he took it to a mechanic and i dont think the guy looked at it he just gave him his opinion on what he thought was wrong. so i think it could quite possibly be the gauge. tonight i drove it around town quite awhile and then i sat in idle for about an hour. still couldnt get it to overheat so i am hoping its just a simple problem like the gauge or the temp sensor would also be nice.

i was digging in the glove box and found receipts that he replaced the tstat in june so thats the first place im gonna start once i get ahold of a heat gun to check it out.
 

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if youre not loosing coolant, it may be just a bad temp sensor & stuck t-stat (pretty common & easy fixes) if yo uare loosing coolant, and its not in the oil start w/ the LIM gaskets (also common, and not too bad to fix) get the alum ones (green) and if its a 3.4 you can do a 3.5 topswap (to prevent the Intake from crappin out) if a 3.8 you can get a UIM from a L26 (05+ 3.8 non s/c gp or lucenre) theyre alum and fix the L36 UIM issues ;)
 

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Discussion Starter #6
well didnt get a chance to go mess around with the car today (since its just a third vehichle that will probably become a dd) but while at work i got a chance to speak with the guy i bought it from and he had the tstat and lim gasket replaced this past summer so im gonna just try a temp sensor first and see what that does. i am leary of the water pump also. still gotta take a closer look at that to make sure its not leaking.

oh as for the coolant temp sensor it is right next to the tstat housing, right.
 

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should be, right below it IIRC, in the LIM itself

I havent heard of to many water pump issues w/ these cars, but fwiw, its a PITA to change, but you can do it w/o removing the engine
 

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Discussion Starter #8
well i havent posted in awhile but finally i got the tstat and temp sensor replaced but still have a weird issue with the heating. it starts out fine and heats good but then while im driving the needle goes back and fourth between about 1/4 and about 3/4. when the needle hit 1/2 or so it will start kicking out heat nicely but then drop with the temp. it goes back and foruth the whole time its running. the temp will also drop when its getting high if i shift into neutral and rev the motor a few times then its fine for a mile or two until this starts all over. any ideas guys? you have alll been helpfull thus far.
 
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