This is intended as a guideline for perspective/new GEN 1 owners. If you have an item to add feel free to post up and I will add it to the OP.
The following items are common issues that can be found on GEN 1 Xterra's. I will try to add pics and a link to the DIY (Do It Yourself) threads for each item.
If you're a new owner it should help you out in fixing and staying ahead of certain issues. If you're a perspective owner it will help you in what to look for as far as problems and possibly help you to bring the owner down in price before buying.
All the DIY threads can be found here.
All of the Factory Nissan Service Manuals can be found here.
Timing Belt. Ask exactly when, and if, the timing belt was changed as they need to be changed every 105,000 miles. The 3.3L V6 engines (VG33E and VG33ER) are interference engines and if the belt slips or breaks it can cause valve/piston damage.
The only indicator you may find for a changed timing belt is going to be a sticker applied to the top of the radiator core support indicating the belt has been changed. Past that you have to trust the owner and his records.
You can do the timing belt your self and will require right around $325 in factory Nissan parts, hand tools, and depending on your skills 6 to 12 hours of your time.
Timing Belt DIY
Torn down, new belt and water pump installed.
Valve covers leaking oil. Most leaks can be slowed or stopped by simply tightening the screws a bit but eventually the gaskets shrink enough to need to be replaced.
Take a flashlight and look at the starter if you see a leak on the passenger side valve cover and check to see if the starter is covered in oil. Oil immersion/intrusion causes the starter to fail prematurely.
You can do the valve cover gaskets your self and will require right around $34 in factory Nissan parts, hand tools, and depending on your skills 1 to 3 hours of your time.
Valve Cover Gasket DIY
Drivers side on mine you can see where oil had been leaking onto the head.
Passenger side note the sludge covering the screws and edge of the rocker cover indicating a leak.
Cracked exhaust manifolds. Nearly all GEN 1 trucks will have this issue at some point. Hard to see the cracks with the heat shields in place but listen to the engine run with the hood open and listen for ticking ex leak noises. Passenger side tends to fail before the drivers. This can be a time consuming difficult job do to lack of clearance between the frame and manifolds. Trucks with a 2" body lift installed are much easier to perform this job on, so much so if a BL is in your future perform it before the manifolds.
You can replace the cracked manifolds your self and will require just shy of $400 in factory Nissan parts, hand tools, and depending on your skills, and whether or not your truck has a body lift, 2 to 6 hours of your time. Aftermarket parts will be much cheaper here.
Manifold DIY
Passenger side note the crack above the O2 sensor. Note the soot from leaking ex gases above the crack another indicator for a bad manifold.
Drivers side thin white line near the bottom running the length of the manifold is a crack. Note the black exhaust soot on the manifold cuased by ex gas leaking from the crack.
Leaking power steering lines. Happens to all of them at some point but it is just the lines for the reservoir usually, not the pressure lines, so easy to fix with bulk hose from auto supply store.
You can replace the leaking lines your self and will require just shy of $20 in hose from your local auto parts store, PS fluid, hand tools, and .5 to 1.5 hours of your time.
There is no DIY at this time.
Passenger side from the top, look for fluid below the PS reservoir on the passenger side inner fender and passenger side suspension.
Passenger side from underneath looking for the gooey mess seen here
Passenger side wheel well skirt will sometimes show the leak as well
Rear main seal leaks. Not much of an issue but oil will collect on the bell housing more of an annoyance than anything. Many times the rear main seal is not even the culprit but rather the leaking valve cover and the oil running down to the bell housing.
Fairly expensive to repair as the transfer case and transmission must be pulled to access the seal to replace it.
There is no DIY at this time.
Seen here on the bell housing. A lot of times it's not even the rear main seal just the valve covers leaking down ending up here.
Leaking power steering gear. Known issue with some trucks and not cheap to fix unless you rebuild the gear yourself. Look for oil on the bottom of the steering gear itself but ensure that is where it is coming from. The A/C high pressure lines can sometimes leak and are located right above the steering gear. A/C compressor oil is green in color but once on the steering gear may appear black so trace the leak.
You can rebuild the unit yourself and will require just over $20 for the P/S Gear Box Major Seal Kit from your local NAPA parts store, PS fluid, hand tools, and 3.0 to 6.0 hours of your time.
Steering Gear Re-seal DIY.
Steering Gear Re-Build DIY.
Example of an obvious leak
Example of the more common "may do this for a couple years before becoming an issue" leak. Notice the very lite sheen of oil on the shaft and nut.
Rusted oil pan. This is mostly an issue in states where they use road salt. The pans will actually rust through and leak oil. You will be looking for bubbled/flaking paint, rust, and obviously oil.
You can replace the pan yourself but be aware on the 4x4 model you will be dropping the front differential and a cross member in order to get the old pan out and the new one in. From Nissan the pan will run right at $240. No estimate for time to repair but a good guess would be 8+ hours.
There is no DIY at this time.
Pic showing a rusted through leaking pan
Leaking High Pressure A/C Line. A leaking high pressure line will cause the A/C system to be either weak or non-functioning as it is leaking freon out of the system and allowing moisture in. Becoming a more common issue as these trucks age and fairly easy to spot. Locate the High Pressure line on the drivers side front. It runs from the A/C condenser to the A/C compressor. You are looking for any oil/sludge on the line itself.
You can replace the parts yourself but I suggest you have the system vacuumed down and refilled by a professional. The high pressure line will run you just shy of $90 from Nissan and you should change the drier at the same time and that will cost an additional $70 plus the cost to vac/refill the system. Replacement time for both items is around1-2 hours.
There is no DIY at this time.
Pics borrowed from Knicol
Pic showing line location on drivers side front. Typically they will leak right where the arrows indicate look for compressor oil on the rubber jacket.
Better pic showing the leak. Note the compressor oil on top of the steering box and that it is green in color. If you think you have a leaking steering box trace the leak it may be the high pressure line.
Thermo Control Element The TCE, also referred to as the wax pellet, is located on the base of the of the throttle chamber and controls cold start idle. As the pellet expands as the engine warms up it lowers the mechanical idle. Over time the o-ring that seals them tends to start leaking coolant usually onto the ex manifold. It's often times an annoying coolant leak that can not be traced as there is no leaking coolant apparent but because coolant is being vaporized, as it hits the ex manifold, it leaves the distinct smell of antifreeze around the engine bay.
You can fix it yourself using basic hand tools and a $1 o-ring. The process of replacing it will generally take about 1-2 hours.
Thermo Control Element DIY
Location of the TCE as indicated by the red arrow
Textbook leaking TCE
Those are probably the most common issues you will find with a GEN 1 Xterra and none of them terribly difficult to remedy. Over all they are well built and very off road capable trucks.
The following items are common issues that can be found on GEN 1 Xterra's. I will try to add pics and a link to the DIY (Do It Yourself) threads for each item.
If you're a new owner it should help you out in fixing and staying ahead of certain issues. If you're a perspective owner it will help you in what to look for as far as problems and possibly help you to bring the owner down in price before buying.
All the DIY threads can be found here.
All of the Factory Nissan Service Manuals can be found here.
Timing Belt. Ask exactly when, and if, the timing belt was changed as they need to be changed every 105,000 miles. The 3.3L V6 engines (VG33E and VG33ER) are interference engines and if the belt slips or breaks it can cause valve/piston damage.
The only indicator you may find for a changed timing belt is going to be a sticker applied to the top of the radiator core support indicating the belt has been changed. Past that you have to trust the owner and his records.
You can do the timing belt your self and will require right around $325 in factory Nissan parts, hand tools, and depending on your skills 6 to 12 hours of your time.
Timing Belt DIY
Torn down, new belt and water pump installed.
Valve covers leaking oil. Most leaks can be slowed or stopped by simply tightening the screws a bit but eventually the gaskets shrink enough to need to be replaced.
Take a flashlight and look at the starter if you see a leak on the passenger side valve cover and check to see if the starter is covered in oil. Oil immersion/intrusion causes the starter to fail prematurely.
You can do the valve cover gaskets your self and will require right around $34 in factory Nissan parts, hand tools, and depending on your skills 1 to 3 hours of your time.
Valve Cover Gasket DIY
Drivers side on mine you can see where oil had been leaking onto the head.
Passenger side note the sludge covering the screws and edge of the rocker cover indicating a leak.
Cracked exhaust manifolds. Nearly all GEN 1 trucks will have this issue at some point. Hard to see the cracks with the heat shields in place but listen to the engine run with the hood open and listen for ticking ex leak noises. Passenger side tends to fail before the drivers. This can be a time consuming difficult job do to lack of clearance between the frame and manifolds. Trucks with a 2" body lift installed are much easier to perform this job on, so much so if a BL is in your future perform it before the manifolds.
You can replace the cracked manifolds your self and will require just shy of $400 in factory Nissan parts, hand tools, and depending on your skills, and whether or not your truck has a body lift, 2 to 6 hours of your time. Aftermarket parts will be much cheaper here.
Manifold DIY
Passenger side note the crack above the O2 sensor. Note the soot from leaking ex gases above the crack another indicator for a bad manifold.
Drivers side thin white line near the bottom running the length of the manifold is a crack. Note the black exhaust soot on the manifold cuased by ex gas leaking from the crack.
Leaking power steering lines. Happens to all of them at some point but it is just the lines for the reservoir usually, not the pressure lines, so easy to fix with bulk hose from auto supply store.
You can replace the leaking lines your self and will require just shy of $20 in hose from your local auto parts store, PS fluid, hand tools, and .5 to 1.5 hours of your time.
There is no DIY at this time.
Passenger side from the top, look for fluid below the PS reservoir on the passenger side inner fender and passenger side suspension.
Passenger side from underneath looking for the gooey mess seen here
Passenger side wheel well skirt will sometimes show the leak as well
Rear main seal leaks. Not much of an issue but oil will collect on the bell housing more of an annoyance than anything. Many times the rear main seal is not even the culprit but rather the leaking valve cover and the oil running down to the bell housing.
Fairly expensive to repair as the transfer case and transmission must be pulled to access the seal to replace it.
There is no DIY at this time.
Seen here on the bell housing. A lot of times it's not even the rear main seal just the valve covers leaking down ending up here.
Leaking power steering gear. Known issue with some trucks and not cheap to fix unless you rebuild the gear yourself. Look for oil on the bottom of the steering gear itself but ensure that is where it is coming from. The A/C high pressure lines can sometimes leak and are located right above the steering gear. A/C compressor oil is green in color but once on the steering gear may appear black so trace the leak.
You can rebuild the unit yourself and will require just over $20 for the P/S Gear Box Major Seal Kit from your local NAPA parts store, PS fluid, hand tools, and 3.0 to 6.0 hours of your time.
Steering Gear Re-seal DIY.
Steering Gear Re-Build DIY.
Example of an obvious leak
Example of the more common "may do this for a couple years before becoming an issue" leak. Notice the very lite sheen of oil on the shaft and nut.
Rusted oil pan. This is mostly an issue in states where they use road salt. The pans will actually rust through and leak oil. You will be looking for bubbled/flaking paint, rust, and obviously oil.
You can replace the pan yourself but be aware on the 4x4 model you will be dropping the front differential and a cross member in order to get the old pan out and the new one in. From Nissan the pan will run right at $240. No estimate for time to repair but a good guess would be 8+ hours.
There is no DIY at this time.
Pic showing a rusted through leaking pan
Leaking High Pressure A/C Line. A leaking high pressure line will cause the A/C system to be either weak or non-functioning as it is leaking freon out of the system and allowing moisture in. Becoming a more common issue as these trucks age and fairly easy to spot. Locate the High Pressure line on the drivers side front. It runs from the A/C condenser to the A/C compressor. You are looking for any oil/sludge on the line itself.
You can replace the parts yourself but I suggest you have the system vacuumed down and refilled by a professional. The high pressure line will run you just shy of $90 from Nissan and you should change the drier at the same time and that will cost an additional $70 plus the cost to vac/refill the system. Replacement time for both items is around1-2 hours.
There is no DIY at this time.
Pics borrowed from Knicol
Pic showing line location on drivers side front. Typically they will leak right where the arrows indicate look for compressor oil on the rubber jacket.
Better pic showing the leak. Note the compressor oil on top of the steering box and that it is green in color. If you think you have a leaking steering box trace the leak it may be the high pressure line.
Thermo Control Element The TCE, also referred to as the wax pellet, is located on the base of the of the throttle chamber and controls cold start idle. As the pellet expands as the engine warms up it lowers the mechanical idle. Over time the o-ring that seals them tends to start leaking coolant usually onto the ex manifold. It's often times an annoying coolant leak that can not be traced as there is no leaking coolant apparent but because coolant is being vaporized, as it hits the ex manifold, it leaves the distinct smell of antifreeze around the engine bay.
You can fix it yourself using basic hand tools and a $1 o-ring. The process of replacing it will generally take about 1-2 hours.
Thermo Control Element DIY
Location of the TCE as indicated by the red arrow
Textbook leaking TCE
Those are probably the most common issues you will find with a GEN 1 Xterra and none of them terribly difficult to remedy. Over all they are well built and very off road capable trucks.