Whats left? The only thing that I can think of is the water pump. How can I tell for sure if it is the water pump?

Thanks

Critical for thermostat, tank tops and water pump.

Discover the power of the button!

Since head gasket failure is extremely rare unless the engine has been overheated. You always check coolant for hydrocarbon gases [use the typical device] and measure pressure build up time and ramp up rate. To confirm.

Using aftermarket parts which are only 95-90% as efficient to new oem may reduce the safety spread.

Really difficult to diagnose without accurate temperature number and a time to rise chart, idle rpm, ambient temperature, ac on/off.

Many times overheats are somethings you forget like the rubber air surround around radiater allowing an air feedback fom engine compartment to the input side of rad. A restricted airflow condenser, dead auxillary electric fan in front of condenser. high idle rpm, more than 50% AF in coolant.

It would also help us to help you if you would answer the questions asked.

To answer your questions, Tech, the water pump doesn't leak from the weep hole or make strange noises.

The car has been heated up but I have never let it get past the safe zone on the engine temp gauge.

What's the typical device you use to check for hydrocarbon gases?

I have only used OEM parts on my car.

What is this "rubber air surround" you speak of?

I just cleaned the air condenser so that shouldn't be a problem. I was suspecting the AUX fan because it didn't seem to be blowing as hard as it should be.

I really appreciate the help, Tech, and others on here.

Aluminum has little tolerance for over heating.

Modified by maxnix at 7:38 PM 10/10/2008

Lets say it did "overheat" how can I tell what damage was done? And if it did do damage to the engine/head gasket how can that effect the cooling system?

The point is tools are necessary along with technical education to use them. At least the ability to follow written instructions precisely.

When does it get hot? Will it sit at idle and overheat or only overheat while driving/cruising?

If you have access to a laser thermometer use it to take some temp readings of the radiator at a couple of points; top, bottom, and each side. There will be some temperature variation but not like a 100*F difference.

1994 Infiniti Q45 - Modified factory air box, Amsoil synthetic fluids
1991 Nissan 240SX SE Coupe --SOLD--

Since a rad may only drop temp 10-15F from input to output.

Almost always the problems are a used old, dirty, bent fin radiator especially after 8 years [depending on mileage].

After market rads while they fit are made of thinner plastic and aluminum, their fin count per inch is less and generally under stress thay perform 10% less than new OEM.

While 10% less may not sound like much adegree here and there soon adds up causing the feedback system [thermostat vs pump] to lose control with a slow steady rise in coolant temperature.

Why it is important to create a graph of coolant vs ambient vs time in 15 second increments from a cold crank for 15 minutes [60 data points] idling in shade.

THEN turn AC on MAX and data log for another 10 minutes.

DO IT AND YOU WILL SEE what I am saying.

Unfortunately you need a CONSULT to see coolant temp as ecu sees coolant temp.

I drive non engineering techs battey with all my engineering data recovery.

BUT THE DATA NEVER LIES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

The GREGORY HOUSE of Automotive Technology

AFTER ALL if you combust X amount of gasoline in Y time at Z efficiency an exact amount of HEAT is generated. The heat can only go 3 places sitting still..
Heat the air underhood, heat the coolamt, or flow out exhaust pipe

Thanks