Warm Weather Overheat 01 Again!

I had to change the radiator in my 2K Max to fix that problem!!%!$@#

Geoff

Good suggestion. Replace the radiator. If that doesn't fix it, then the only thing I could think of that I wouldn't want to think of , is a blown head gasket. Last resort kind of thing.

CD

Even my mechanic and the tech at Nissan are scratching there heads. Latest guess is the water pump "baffles". These are the fins that make the coolant circulate. I am told that some of these are made of a type of metal and some are made of a type of plastic. No one kows for sure till it is removed. Its about a 300 dollar job at my guy so thats probable 600 at dealer. Any thoughts on this theory? BTW thanks for the responses as they are always appreciated.

Tony C.

Actually, its a 400 to 500 job for the water pump. The pump has metal fins. I find it interesting that the Nissan mechanic doesn't know for sure what type of water pump you have. Hmmmm. Look at it this way:

replacing the radiator: 300 or less. You could do it yourself even. repalcing the water pump:400-500 replacing the head gasket: very very expensive

CD

Are you sure that it actually does overheat. Could it not be a problem with the temperature sensor or guage?

Al Moodie.

Good question. When I allow the gauge to approach the first HOT indicator, I see that the overflow jug is beyond the "full when hot" indicator and it is bubbling. The weird thing to me is the quickness of the temp gauge to drop back down to just below center. AC of course will become warm as gauge goes up. When I turn off ignition even for one minute then re-start, gauge drops right back down to normal range within one minute. I am going to order new thermostat from the dealer this time just in case the aftermarket one was faulty. I'm probably wasting my time but what the heck. As always any ideas from the group is very much appreciated, Thank You!

Tony C.

This statement makes me supect the temp may in fact be normal, but the sensor is faulty. Water will flow and bubble into the overflow container as the coolant rises in temperature from cold to normal operating temperature, this is normal. I would replace the Engine Coolant Temperature Sensor, it should be a cheap fix, cheaper and easier to replace than the thermostat.

Then again if the problem only happens in warm weather that would mean the cooling system can cope with heat dissipation in cool weather but not in warm (greater load). That suggests a partially blocked radiator or some other partial blockage in the cooling system.

Al Moodie.

Have to disagree here. First, a bubbling overflow tank is not normal. Something's wrong. And regarding the coolant temp sensor; when it fails, the car tends to run cooler than normal.

CD

Hi Codifus,

When the engine is cold the water level in the overflow resevoir will be at "cold" marking. You start the engine, the water heats up, and expands into the overflow tank, and the level rises to the "hot" marking. Wont you get bubbling at this time? No, you are probably correct, there should be little or no air in the system, so there should little no bubbling as the engine heats up.

Again I bow to your superior knowledge. All I really know is that if the coolant temperature sensor is faulty, you will get a faulty temperature reading.

If the coolant temperature sensor is faulty, how does that make the engine run cooler. What does the coolant temperature sensor affect? the thermostat, fans, some other temperature adjusting mechanism?

Educate me please.

Al Moodie

OK, regarding the temp sensors, on this maxima there are 2. One sensor actually tells the ECU what tempurature the car is. The other one is linked to the temp gage that you view on the instrument panel.

The ECU one is the important, critical one.

When that sensor fails, it tends to under-report the tempurature to the ECU. If the car's real temp is 240 degrees, a failing sensor will tell the ECU is 140 degress. The ECU then thinks that the car is still cold, thereby keeping the fuel maps on the rich side, you know, like when you first start the car in winter. Running rich makes a car run cooler because of the excess, and hence unburnt, feul being thrown into the cylinders.

Symptoms of a bad temp sensor: weaker engine, bad gas mileage.

CD

Most of the the Maximas have two temperature sensors, one that feeds the gauges and one that feeds the ECU. If the "other" one is bad, you won't see any cessation of function on the gauge.

If you've got obvious flow into the overflow tank as the engine warms from cold to normal, that usually means a bad radiator cap is opening at too low a pressure. It shouldn't be moving anything into the overflow tank until its fully warmed up and the pressure in the radiator starts to exceed the cap rating. In any event, there shouldn't be any bubbles.

If it continues blowing bubbles into the tank and proceeds directly to overheated, that is a classic symptom of a blown head gasket.

I think your first priority is finding the source of the bubbles - seeping water pump, pin hole in a hose, etc. My daughter's 240SX will behave as you describe if there is an air bubble trapped in the vicinity of the thermostat (usually right after a coolant replacement).

=== Myself I would find a good radiator repair shop and get it fixed before you ruin the engine.

O.K. I appreciate all responses, let me ask this. I have seen an additive called "Water Wetter" made by a company called "Redline" It states that it will reduce engine temp. by 20 degrees and is perfectly safe to add to the existing coolant. Anybody have experience with this stuff? And is 20 degrees enough to solve my probem?

It's not a problem solver. Water Wetter just makes your system run more effficiently. Fix the problem first, then add water wetter.

CD