Good afternoon all,
I currently live in AZ and during the summer, my xterra overheats quite often. Last summer I replaced the water pump, radiator, fan clutch, temperature sender, and a miscellaneous engine part. I have also made sure it has the correct amount of coolant in it, yet it still overheats on hot days. Before I did the replacements, it was overheating while driving no matter the temperature, after the upgrades, it only overheats when the temperature reaches a bit over 100 and I have to travel over any type of mountain. My dilemma is that I have to leave the valley and therefore go over the surrounding mountains mid summer. Is there anything that I could do to limit or eliminate the overheating issue at this point or is it just something I should expect with a vehicle of that age.
Sadly knowing the amount of effort and work going into whats already been done and having to deal with similar things in one of my overland rigs here in Nevada as Vegas believe it or not gets into avg temps of 103* often with 2 months of the year near 118* +/- some.
The radiator you have or are using isnt big enough to hold enough coolant to keep temperatures where they should be. NOT so much due to just driving around town but in heat, HIGH heat at that, slow speeds where not enough airflow is coming across the radiator, and your putting the truck to task albeit.
Swapping out to a larger rad isnt exactly enough, it'll do the same thing only take a little longer. Its time to free up some parasitic loss from the Clutch fan and do an E-Fan setup (Electric fan setup) if nothing better, the fan itself may be old and bends with the heat (needing replacing). Whereas some will argue that the current draw from the fan is worse than the drag on the motor, yada yada.. either way its a draw on the engine, its just preference. Not to mention, SHOULD you go elsewhere and encounter a water crossing, you cant turn off a clutch fan, but you can an E-Fan setup.
Other suggestions, if you replaced the T-stat with a stock one. Its likely a 195*-210* temp. Swap it out for a 172.4*. like Mishimoto
https://www.12degnorth.com/product-page/nissan-frontier-xterra-performance-thermostat-by-mishimoto version. Opens up earlier and gets coolant flowing. Yours may not have the same in the 02' but I guarantee you someone makes a 180* T-stat for your engine.
Things like oil coolers, Trans-coolers, all of these things can have an effect on the engine temps. Consider doing an oil cooler. I think Mishimoto may have a universal style one, may want to call to be sure of that. Keeping oil temp down keeps engine temps down which keeps coolant temps down.
Also consider throwing in a bottle of their coolant additive. They claim it keeps coolant temps down which I am sure it does but I've not used it. My only experience with a coolant additive is "Water Wetter" from Redline Oils (available anywhere even Autistic Zone and Oreallys). Its about the same cost but they at least tell you you can expect 10*-12* reduced temps. That's fairly good to be honest, you'll need or want 2 bottles either way you go.
Trans cooler, if your's still runs inside of the Auto radiator, consider it preventive maintenance from S.M.O.D. (if you haven't done so already) and going to an external that's a bit larger with more surface area to cool down better. Several on the market from Mishimoto to B&M, Haydon... etc
An old school trick which seemingly is popular in the import performance crowd set on Ridiculous mode, is the advent of removing the rear hood gasket. It rides along the rear of the hood line inside the engine bay and on top of the firewall. As a test remove it, you may need to shim the hood with a couple washers on the hood hinge bolts. Just dont do like the Honda Civic guys and add 20 washers to each bolt so the hood looks like they tried opening it from the opposite end like a 68' Vette and broke it.
Outside of that consider some retraining of your driving habits. i.e. Climbing a long stretch of tarmac as you stated. Don't try to keep up with traffic and do 75 MPH+. back it off to 55-60 throw it down a gear or 4th if its a manual and ride it out. Most idiots doing that aren't dragging a carcass of a vehicle around like us, they certainly are more efficient at power to weight and that's why they slingshot by, and those that are in SUV and large trucks doing 80-90 MPH - their vehicles are either often in a state of repair or don't last long anyways because they beat on them and sell it to get a new one every two years and keep that perpetual debt can kicked down the road.., or funnier yet, its a rental and just don't care its not theirs.
Not saying that's you, I'm just painting a picture for reference cause.. well someone fits the description because I witness it everyday living in the Vegas Bowl so there is more than one.
As an added thought. May consider taking that list of ideas and running it backwards. Try the water wetter, T-stat, then an Efan/Fan replacement, then as things get more intense for performance related options then you might have to get a little dirty and start adding the other items.
BTW did you have the system reversed flushed by chance to make sure you have no obstructions in the system by chance?
hope some of that helps
