# Overheating problem



## parashbro (Nov 7, 2005)

Hi all,
I have an overheating problem with my Nissan Altima 1994. I recently bought the car about 6 months ago and I have been driving it back and forth to work which is about 70 miles one way. Mechanic said my water pump was leaking. So I changed it. It has no visible leaks now that him and I can stop, but it doesn't stop overheating. So he told me again that my thermostat was the problem. I changed the thermostat and it doesn't stop there. He says, he can't see where the leak is coming from, but everytime I fill up the coolant in the reservoir, I check in the next 2-3 days and its low. I fill it up and its low again. Now, he says my head gasket could be blown. But before I changed my thermostat, he did a head test and said it was doing ok. Could it have blown, when I drove the car when the thermostat was bad? Or the thermostat was never bad in the first place? Is it the blown head gasket? Please help.


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## jserrano (Oct 27, 2004)

A head gasket will age and eventually go bad when the engine is running in a overheated state for a good couple of minutes. Once it goes bad it will overheat the engine much faster and cause other symptoms. You can do a compression test, leak down test, and take a vacuum reading and it should help isolate a bad head gasket. Visible signs like white exhaust pipe smoke, coolant reservoir boilover, radiator coolant milky bubbles, etc. can help identify that as well.

There are some coolant pipes running along the backside and underneath of the intake manifold. I've heard of people having pinhole leaks that would spray onto the engine and you'd hardly even notice it.

You never mentioned, whether the cooling fans were ever coming ON when the engine was overheating. At what point of the temperature gauge do the fans come ON? The fans are controlled by the ECU as commanded by the coolant temperature sensor (CTS).

One quick test you can do to see if the thermostat is lazy or stuck closed it to simply remove it altogether. Run the engine when it has cooled down. In the mayority of the cars, this should cause the car to take a long time to reach the middle of the temperature gauge. If it still overheats in a short period of time while the engine is running then you really want to take another look at that head gasket.


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