# 2002 sentra problems



## mmmisha (Feb 17, 2012)

so after im driving for about 5 mins and the car warms up (i live in canada and its kind of cold right now), the temp gauge goes up to h. i crank the heater which is now blowing cold air - if i drive over 60km the hot air kicks in again and the gauge drops back to normal, just under halfway. if i come to a light, or drop below 60 the cold air comes back and the gauge goes up again... i just had the thermostat replaced in the summer. theres no smoke/liquid coming from the tail pipe and the oil looks good.... any suggestions what this could be and what i can do?

the car has 200k on it, and aside from the thermostat, i havent had any problems in the 6 years ive owned it.

any help would be appreciated
thanks


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## LSDisk0 (Dec 8, 2011)

my friend had the same problem, but a different car; he replaced the heater core and that fixed the problem.


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## smj999smj (Jan 1, 2006)

I would check for a blown head gasket before jumping into a heater core replacement. Are the radiator cooling fans working? Coolant level full? Any air bubble coming up through the coolant when the engine is hot?


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## LSDisk0 (Dec 8, 2011)

touche, smj. 
He replaced the thermo, so i'd have to assume he would have checked the collant level


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## mmmisha (Feb 17, 2012)

*she replaced... and coolant levels fine, no leaks that i can see.
should i be able to see air bubbles? if there are/nt some, what does that mean?
what would be other symptoms for a blown head gasket? 

thanks


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## mmmisha (Feb 17, 2012)

*she replaced... and coolant levels fine, no leaks that i can see.
should i be able to see air bubbles? if there are/nt some, what does that mean?
what would be other symptoms for a blown head gasket? 

thanks


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## LSDisk0 (Dec 8, 2011)

my apologies.
Search around your head for leaking fluid, thats one way to tell if it's cracked. and if you had air bubbles they would most likely be in the system where you cannot see, if I am correct, which even if I think I am smj corrects me lol


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## SPEEDO (Jun 9, 2003)

which engine? 1.8? (2.5 also has a "water control valve") if you have a air bubble in the system, you might hear a gurgling sound, to help the air bubble to escape, raise the front of the car (engine running, cap off)
if you have a bad head gskt, chances are it will not been seen, it will be between cylinders, you can run a pressure test or pull plugs (see what color they are) to help you identify if that is the problem... are you losing coolant? white smoke from exhaust? sweet smell?
some ideas anyway.....


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## smj999smj (Jan 1, 2006)

I use a Lisle "spill-free funnel" (see link below) to check for head gaskets. Remove the rad cap, install the funnel, add a little water or coolant so the level can be seen in the funnel, then run the car at 2000 RPM for several minutes. If a fairly steady stream of bubbles is seen coming up through the coolant (assuming you haven't just serviced the cooling system), chances are likely the head gasket is bad; something that is not uncommon on the 1.8L. Whether it's a blown gasket or cracked head can't really be determined until the head is removed and sent out for inspection, but most of the time it's just the gasket. Other ways to test is removing the spark plugs and pressure testing the coolant system or performing a cylinder leakdown test, which requires a leakdown tester and an air compressor. The Lisle funnel can be found in most auto parts stores for around $20 and comes in handy when bleeding air pockets after service the cooling system.

Amazon.com: Lisle 24610 Spill-Free Funnel: Automotive


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