Here is some more detailed information... please remember that I am not a mechanic... for $90 from NAPA i got a TB, tensioner pulley, and three belts (AC, alternator and powersteering/waterpump. i ended up not replacing the water pump because it was not leaking and the job did not seem that hard. so once the waterpump leaks i will start all over. same with the seals. 2. i have a copy of the haynes manual that i read about a half dozen times before i started. it was kind of intimidating to dig that deep into the xterra. but i ended up using it more as a picture reference a few times... like making some notes for future reference. 3. it is a 3 hr job that took me 9 because i did alot of looking and cleaning... like cleaning the radiator and using antiseize compound on each bolt i put back on. main tools needed... metric sockets... mostly 10mm socket and 10mm open end wrench, 12mm and 14mm sockets and a 27mm short socket for the crank bolt... a harmonic puller... not included were M-6 60mm or 75mm long with some washers. 4. first step... drain the radiator. there is a shroud under the car that unsnaps that gives you access to the drain plug. pull hard and slow on the plugs or snaps... wiggle them back and forth and they will come loose. there is a philips head screw under the radiator in the middle that comes out. i put a large plastic pipe to keep fluid from splashing everywhere and drained into a mcdonalds pickle bucket. i thought that i would reuse but instead put in new fluid. i think it took me almost two of the 50/50 mix jugs. second, once the radiator fluid is out, disconnect the auto transmission lines if you have an automatic... i don't know what the manual transmmissions have... buy some new transmission line... it is pretty standard stuff. disconnect at car side for easy removal. i put some big bolts in the rubber line to prevent drainage and a couple of plugs from extra new hose (doubled over and tied with wire) to cover the metal lines. take the four 10mm wrench size bolts off the fan and rest the fan inside the radiator housing. next disconnect the radiator hoses. the top one came off easiest at the car side... the lower one from the radiator side of the metal pipe. that whole piece with the metal pipe will eventually be taken off. take off the radiator mounting bolts and associated parts to clear a path to get the radiator out. wiggle the radiator out. i pulled a little bit then got under the car and moved some hoses around. i don't think that i forgot anything... i next took a break and hosed off the radiator... ran a stream of water from back to front to push out all the dirt clogging the fins. take off the fan belts... starting with the AC find the tension wheel and loosen its nut then find the belt tensioning bolt and loosen until you can slip the belt off. with the radiator off they are pretty easy to spot.
next, put the 27mm socket on the crankshaft bolt and attach the breaker bar and pipe if needed. put the breaker bar and extension if you need it on the ground angled towards the drivers side... have someone tap the starter.. mine came loose easy. remove bolt. use harmonic puller to remove pulley... the M-6 bolts go in two holes that you should be able to see or feel. it may take some rust remover or grease to get them in since you probably have some rust in the holes. the crankpulley is on a fairly long straight shaft... the harmonic puller gradually pulls the pulley off... once you get it started and moving you can remove the puller by wiggle by hand. it is pretty heavy so try not to let it drop.
take off the AC belt tightner assembly... a few bolts... disconnect alot of the electrical connectors and hoses that run along the top front of the engine so you can get them out of the way. Note: i had a note pad that i made notes on then tore off and put associated parts and bolts with on the garage floor...
now, if i have not forgot anything, you should be at the meat of the project. remove the TB cover bolts. with a piece of paper make a diagram because most of the bolts are different lengths and must be put back in the same hole. with all the bolts off you can shimmy the two piece TB cover off. next, if you have not done it, get the first cylinder, front left cylinder as you look at engine at top dead center. i am not sure but i believe if you note where the #1 pin is on the distributor cap, remove it, then rotate the engine with the starter or by hand by slipping the crank pulley back on and turning engine clockwise as you look at it until the rotator is pointing at where the #1 distributor pin is then you are at top dead center of the firing. if you use the pulley turn slowly and the engine will turn. once you have the engine at top dead center of the power stroke, look closely at the camshaft pulleys and the crank pulley. there are two dimples on the housing behind the camshaft pulleys... there should be a dot on each camshaft pulley (a cam tooth will have a depression) that lines up with the dimples. because my TB stretched they were not exactly lined up. the crankshaft pulley should have a dot of white paint on a pulley tooth and a white dot of paint on the engine housing. if this is all lined up then you can loosen the TB... loosen the tensioner bolt then with a hex wrench turn the tensioner i think counterclockwise to loosen... note the spring... it is easy to get back on... my TB with 108k miles looked unworn but was loose. enough people scared me about valves going through pistons that i did not want to take a chance. the new TB belt i got from NAPA had a dotted line beside a solid line... you'll use the dotted line. look for another line with an arrow that says FR or front. make sure the arrow faces you then put the dotted line over the tooth on the left cam (as you face the engine)... there should be a solid line that will go over the dot on the right cam... importantly, there are 40 belt teeth between the lines. because my belt had stretch some, i had to turn the right cam a little counterclockwise to get things lined up... or 40 teeth between the camshaft pulley dots. once this is done it is time for a break... put a white dot on the outside of the TB where it will line up with the crankshaft pulley... there should be another line on the belt but it is hard to see once you get the belt on... use a crayon, whiteout or something... get belt back on... line up the camshaft dots with the pulley lines... left side dotted line over the cam pulley dot... get the dot you put on the belt over the white dot on the crankshaft pulley.. .there are 43 teeth between the right cam and the crank... doing your best to keep the belt teeth in place, get the tensioner pulley back on... don't forget to put the spring from the old tensioner on the new one. with a hex turn the tensioner clockwise until the spring is tensioning... there is a stud sticking out that the spring will push against. make sure everything is lined up once you have the tensioner ready to tighten... it took me a few times to get things lined up. tighten until you put about twenty pounds of pressure on the top and you cannot push down more than a half inch.
i put the crankshaft pulley back on and turned the engine around a few times... if you have a strap wrench this can be easier... i used gloves, took my time... there should not be any metal valves hitting pistons. if nothing moved much and the belt was put on like the old one then there should be no problem. put everything back together... put the distributor back on... wiggle the crankshaft pulley back on... put crank bolt back on... i only tightened mine as best i could with an old belt wrapped around a pipewrench and placed over the pulley. an impact wrench or strap wrench would give you some more torqueing power. i got mine back to maybe 70 ft pounds but plan to get a friend to use an impact wrench for a final tightening. replace transmission hose on radiator... no real notes on reassembly... wear gloves when you can because there are some sharp edges. the fan is easier to put on if you can get the bolt to the top to put the nut on... or put the fan back on before tightening the waterpump and powersteering belt... don't forget to put the radiator plug back on... i did not loose enough automatic tranmission fluid to need any... i bought a quart so added maybe a half a pint... when done it should start up... i had to go back and tighten up a few belts so make then tight of you cannot push in more than a half inch where therer is some distance between pulleys.