Okay I've been fighting with my 2000 X for months now. I took it into my Nissan dealer and had them run a full diagnosis on it. It came back that my radiator and lower hose needed to be replaced, costing about $850. I did some research on here and looked at how difficult it would be to do the work myself. Found all the parts online, and replaced the radiator, upper and lower hose, all of the hose clamps, the thermostat and the temperature sensor. I figured it would be easier to replace anything that could have gone bad with the couple overheatings I had encountered. Put all new coolant in, and bled the system multiple times in order to ensure that I do not have any air left in my system. I drove to our lakehouse this past weekend, and stayed at a normal temp until exiting off the highway when my car overheated. I drove on the highway for about an hour, going between 55 and 75 mph. We thought there might have been air in the system still, so I went through the bleeding process again. Same thing happened on my way home from the lake. I can drive all around the cities going 60 mph to and from class with no issues. It only happened after driving on the freeway for an extended period of time. I asked Nissan to specifically check my head gasket, they said they tested the pressure and it was fine. I also am leaking a small amount of coolant still, while all of my hose connections are dry. So I have kinda limited it down to the fan clutch or the water pump, but I am not exactly well versed on cars or know much of what I am talking about except for the research I have done. Does anyone else have any ideas? Everyone I have talked to isn't really sure of what is wrong. I appreciate any help that I can get. Thanks so much!

Nelsonea good morning! As there are few places coolant can really go without leaving signs except for internally it can evaporate due to excessive temperature. your over heating after highway speeds could cause a loss but not excessive loss. There are a few things to try so that your not just changing parts to eliminate options. Two very strong ideas are what you already mentioned, the pump and fan. Both your ideas can be easily checked in the driveway.

Start the X and get her to running temp, top her off, set the A/C to max, get a cold beverage and wait! With highway driving your pushing ample amounts of air through the rad and cooling through basic properties of forced air and pumped coolant, then at the point of slowing your system then relies upon the fan to provide that same air and pump to cool the engine down but if either one or both is not up to par the system will fight to recover from the load and then not exactly over heat but run in excess of the norm or yes over heat. So by allowing the X to sit and run for an extended amount of time at idle and then revving the engine to say 2500-3000 RPM's you can rule out both of these possibilities.

The fan should not just spin freely with the X off (clutched/therm), there should be resistance if(clutched) not really if elec. and with therm yes/no. Clutched/Therm models should change volume as in tone or loudness as the temperature rises when running or as the ideal rises it should spin faster as the clutch engages with the higher RPM's. (Robb a Ford Ranger of its Elect. Fan system, say 05-12 at your local salvage yard. The complete elec. system on those is simple and will fit. one less question because when its bad you know it, it just simply doesnt come on at between 199-210 degrees!)lol

At running temps and with good circulation the hoses should have resistance from the pump creating pressure, both upper and lower hoses. They should also be hot not one hot and the other mildly hot/warm. At running temp your heat should be hot with the blower at max, if the heat lowers or becomes cool this also is a sign the pump isn't up to par and or there is a blockage.

Head gaskets can be tricky as they can be bad and still show good pressure however if shes burning antifreeze due to a gasket the plugs and exhaust are your best place to research that issue as the plugs will collect residue and the exhaust will smoke a little and or smell sweat on occasion. The performance of your engines idle, acceleration and MPG can suffer greatly with a bad head gasket showing good pressure readings. There are to many variables involved to just state oh the pressure is good so the gaskets are good. I Wish it was as easy as that!

Sorry to run on, I hope this helps!

This is a really confusing somewhat contradictory series of descriptions.



I'll take a stab at at least trying to help summarize your plight:

1) You were over heating, but under unknown conditions. ("A fight"?)

2) The dealer said you needed a new radiator and lower hose.

3) You decided to instead do a radiator, hoses, thermostat and temp sensor, figuring the shotgun approach was in order.

4) Its still over heating...but, at low speeds (pulling off the road), possibly on the highway, possibly not, as you are a bit vague about what was happening...both seeming to say it was fine (To class and back at 60 mph), and also seeming to think there was in air the system at the same time...so, I'm not sure why, unless you were over heating? So, its over heating on the hwy, and, at lower speeds too?

5) You're missing a little coolant, but don't know where its going.


Please correct/fill in missing details for the above as appropriate.





Next steps that might end up being a good idea:

1) Do an OBD port reading in real time when the dash gauge says you're over heating. The dash gauge is wonky, and, most wonky after the thermostat is changed or it is messed with....reading high, on an intermittent basis (Which you report). The OBD/ECU uses a SECOND temp sensor that is in a different location, and, which is more reliable, and which gives the readout in degrees.

If during over heating, the OBD says its NOT too hot, then, the sensor by the thermostat is wonky, and, you're not actually over heating.


2) If the fan clutch is the issue, its not typically an issue at high speed, as the wind through the grill is providing more CFM for cooling than the fan could anyway. If off road, in slow traffic, etc, is when it over heats (Instead), then the clutch is more suspect. You can test the fan clutch to see if its working.

3) I didn't notice how many miles you had on it. If over 105k, it was due for a timing belt change, and, most people do the water pump when they do the timing belt....as they have to open it all up anyway, etc....so, depending on the maintenance history/mileage, you may need a water pump.

4) If the radiator cap is a wee bit loose/leaks air, you loose pressure, which allows the coolant to boil/suffer cavitation, and that can both cause a small loss in coolant, as well as more over heating.

5) If the heater core or the hoses to that are leaking, you can lose coolant, and pressure, as well, leading to an analogous problem.

6) I don't know you, so, just in case, when you add anti-freeze, you reduce your ability to cool. IE: Pure water cools better than water and anti-freeze. So, too much anti-freeze makes it over heat more easily. 50/50 is typically considered an OK ratio...more than that is worse (As far as cooling goes). Lubrication and not FREEZING are another story.

7) Merely over heating can cause a spike in pressure and release of steam, and, that steam equals a loss in coolant all by itself. IE: You don't NEED a leak to lose a small amount of coolant if you are over heating.

8) Look in the engine oil for emulsions (Creamy stuff) and in your radiator coolant for a rainbow sheen (oil)...to see if the two are trading fluids, as a back up.



Run through the above, and see what makes sense.

Nelsonea, hey another member pointed out a possibility on a different post!

X-wrench stated in another cooling issue about debri build up between the A/C condenser and radiator causing issues, that to could be a possibility in your situation less the build up and more the condenser fins full of debri. When you changed the Radiator was there anything between the two?

This happens in the desert with military equipment alot, the set ups are different mostly but the issue the same! We do not see it as much around central NC any more mostly due to everything is payed now and manufacturers have revamped the openings in which air flows, to be more directional with less openings for air/debri to travel around the condensers. This does lead to condenser build up which in return clogs the flow to the radiator as well!

In years past however build up between the two was a common thing to see. We, my family that is own a salvage yard and from time to time I still pull a A/C condenser that has clogged fins due to bugs, road grime, trash and a small build up between the two parts.

Might be worth a look!

Okay so regarding the questions you have asked...

I know what conditions my car was originally overheating....whenever the engine would heat to normal operating temperature and the radiator was supposed to kick on - it would not work and result in overheating. In order for my X to overheat now, I have to be driving on the highway or freeway for an extended period of time. Once I exit the freeway, and only after I exit it, will it overheat.

I replaced pretty much everything in the cooling system instead of just the radiator and lower hose because the other components had not been changed out previously, and I wanted to just do it all at once since the extra parts did not cost much more.

Of the coolant I have noticed missing, it has ended up on my driveway or garage. It is very inconsistent in which conditions it will leak, but I know that it is leaking out and endeding up on the ground. I have checked all of the hose connections, and all are dry so I am sure they are not leaking anything. The slight loss of coolant does not correlate to when my car has overheated, since I have noticed small puddles on my driveway long after the overheating occured.

Upon replacing the radiator, I also installed a new radiator cap.

The timing belt went out about 25,000 miles ago, and therefore that was just recently done. Our old mechanic (who did the timing belt) did not document very well and I am trying to get in contact with him to see if he replaced the water pump at that time.

I have always used a 50/50 mixture of antifreeze and water.

I am not really sure about the heater core...or how to tell if it is bad or if something is wrong with it.

I did an oil change last week to check if there was anything in it, and it was all clean.

OK, I assume the "Radiator kicking on" meant the radiator fan, so, that implies its the fan clutch.

IE: When first driving, its cold....you get up to speed, and there's heat to be dissipated, but wind speed from driving fast enough is cooling it just fine (And a fan typically is clutched out anyway), but, when you slow down, its still hot, but, there's not enough wind speed anymore to cool it, and, unless the fan would kick on, it would continue to over heat.


If its hot and there's AC condensation dripping, that could explain puddles after parking....and, if you ensured that the puddles were ANTIFREEZE and not condensate, then, the leakage was either evaporating from the hoses and connections before you could check them, or, its coming out to the bottom of the truck from a location that you were not checking.

You could add UV dye to the coolant, drive around, and then use a UV light to see where it leaked from, etc. That helps to locate trickier leak points....and/or confirm the puddle has no dye in it and is not coming from where you thought it was, and so forth.

Steam from over heating, again, can explain some losses all by itself, without a "leak"- but, puddles need another explanation.



Check the fan clutch.