Water Pump Replacement
Typically, the water pump will need to be removed due to the water pump failing or the water pump O-ring seals (2) failing with age. You may get coolant leaking from the weep hole toward the front of the engine with the inner seal failing. Some will warn that the use of silicate-containing antifreeze will ultimately cause injury to the water pump impeller. If your seals are the only faulty items, it is possible to order the two seals separately and to re-install the old pump. However, the water pump replacement is technically difficult owing to the limited space with which you have to work, so for the sake of piece of mind, it may be just as well to replace the entire water pump. Some 4th generation Maxima's also suffered from faulty timing chain tensioners and some would argue that the part can become "tired" over time (mainly the inner spring), so you can elect to replace the timing chain tensioner as well since it will have to be removed anyways.
- metric box-and-open ended wrench set -- I highly recommend a ratcheting wrench set (ie. GearWrench)
- metric socket wrench set -- standard 3/8" will suffice but the smaller profile 1/4" set will be better.
- telescoping magnet -- you do not want anything falling into the timing chain cover. When removing hardware, apply the magnet so nothing is dropped accidentally, or if it does, you can hopefully fish out the part.
- telescoping mirror (optional)
- RTV sealant -- needed to reseal the tensioner and water pump covers
- two M8 x 40mm bolts -- for "jacking" out the water pump
Water Pump Removal
The water pump is driven by the timing chain, so removal requires removing the timing chain tensioner to create slack in the chain.
(1) Jack up the front end and place jack stands. Remove the passenger side wheel and plastic splash guard. Drain the coolant -- save the coolant in a bucket for reuse if it is still relatively new.
(2) Identify and remove the timing chain tensioner access cover and water pump access cover attached to the (passenger side) timing chain cover. They are boxy, outwardly bulging, black metal covers, each attached by four 10mm screws, as seen the centers of the pics below. You will have to gently pry them off because of the gasket sealant applied around the edges. The timing chain tensioner access cover (below, left) is rearward of the motor mount whilst the water pump access cover (below, right) is in front of the motor mount. Note that the water pump access cover is obstructed by the alternator tensioner pulley (removed in pic)--this will need to be removed along with the belt by loosing the center nut of the pulley, loosing tension on the belt, and then the three bolts on the bracket. Because the pulley will be removed from the bracket, be sure to make note of re-install order of the nut and washers before and after the pulley. Removing the power steering belt is optional: it is more work but may make the job easier by creating more room around the timing chain tensioner area.
Here's a pic of the alternator belt tensioner pulley removed:
(3) Remove the timing chain tensioner.
First, familiarize yourself with the position and components of the timing chain tensioner. You can see it from the acute angle you have looking down into the open access port but I used a telescopic mirror to get a better view of the tensioner as shown below. The second picture is of the timing chain tensioner removed. Pay particular attention to the spring-loaded piston. You first must remove the two long retaining bolts (10mm) and then keeping your thumb on the piston to keep it from springing out, carefully remove the tensioner as one unit. If you let the piston shoot out (as in the picture, right), you run the risk of having the spring or the piston fall down into the timing chain cover which you must avoid AT ALL COSTS. Also note that the long bolts have washers which have the potential to fall in as well so pay attention to remove the bolts horizontally until they are removed from the cover area. With the timing chain tensioner removed, you will now see the timing chain tensioner guide fall into view. Now turn the crank pulley counterclockwise roughly 20 degrees to create chain slack on the water pump. Note: some will say that removal of the tensioner is NOT required to create slack on the timing chain; that only compressing the piston and holding it back with a pin/paper clip is sufficient. However, this was no where near sufficient for me when I tried this. Also, some have suggested putting a mechanic's towel or a sheet of aluminum foil down to block any possibility of anything falling into the timing chain cover.
(4) Remove the water pump.
There are three 10mm bolts with washers holding the water pump in place. Remove these, again being VERY careful not to drop these short bolts or their washers down into the timing chain cover. Then use the M8 x 40mm bolts to jack the water pump out (see pic below, left). The top and the bottom holes (that you just removed the retaining bolts from) are also threaded for the M8,1.25 bolt. Take successive turns tightening the screws, no more than one full revolution each. As the pump gradually starts to come out, be sure to lift the timing chain off the gear teeth on the water pump so that the timing chain does not become damaged. Once the water pump is far enough out that you can move the unit by hand, remove the two M8 bolts because there is not enough clearance to remove the pump with them still in place. The just turn and wiggle the pump at different angles up and out of the tight space. Do not be surprised to see a gush of coolant spill out from behind the water pump and down into the timing cover. Loosening the water pump coolant drain bolt minimizes the spillage but it is still pretty significant. You will need to drain and refill the oil at this point because of this.
(4) Drain and replace engine oil/filter.
Water Pump Installation
(5) Install the water pump.
Place the new inner and outer O-ring seals on your new or reused water pump. Coat the seals with coolant. Once again, turn and rotate the water pump into position--paying particular attention NOT to let the new seals come into accidental contact with any metal surface or they can be easily damaged--and very gently push into place. While doing this, you will have to push the limp timing chain up and out of the way. Reinstall the 4 short retaining bolts with washers, again being careful not to drop anything into the timing chain cover. Make sure the timing chain falls clearly over the teeth of the water pump gear and turn the crank pulley 20 degrees clockwise to tighten up the timing chain Again, verify that the gear teeth are firmly engaged with the timing chain.
(6) Install the timing chain tensioner.
To reinstall the timing chain tensioner, you must "cock" the piston all the way into the tensioner body and prevent it from "unloading" by inserting a pin or a small paper clip end into the small pin-sized side hole near the front opening. I would recommend attaching a string to the pin or paper clip in the event that it should fall out and accidentally fall into the timing chain cover. Next, you must position the cocked tensioner back into position by pulling back on the timing chain guide which has since fallen in the way. Then reinstall the two long retaining bolts. This can be frustrating because of the limited space and because this is mainly done by feel. Again (I can't say this enough), do not let the bolts or their washers to fall into the timing chain cover and be careful not to accidentally pull the pin/paper clip out, unloading the tensioner. Once successfully bolted up, you can then remove the pin/paper clip. The piston should pop out and contact it's similarly cylindrical counterpart on the chain tensioner guide.
(7) Replace covers.
First clean both timing chain tensioner and water pump access covers and mating surfaces on the timing chain cover of any old gasket material. Use a degreaser (I used brake cleaner) to make sure no oil residues have fouled the surfaces. Apply high-temp RTV gasket sealant (ie. Permatex) to the cover borders and reattach and bolt securely. Note: this can be quite difficult and messy because of the limited space--have paper towels or cleaning wipes handy! Allow the sealant sufficient time to cure.
(8) Final steps.
Replace alternator belt and tensioner pulley. Replace coolant. I would recommend filling the coolant reservoir a little ABOVE the "max" line in anticipation that a significant amount will be drawn into the cooling system to replenish the coolant that was lost to spillage when the pump was removed.
Start up the car. Do NOT be alarmed to hear a horrific chain rattling noise. The noise will eventually quiet but may not go away even when idling for a while. Rest assured that the noise will go completely away after a short drive around the block. You may also hear a gurgling/bubbling sound as the water pump is pumping coolant AND some air in the system. After a long drive to get the engine nice and warm (consider turning the heater on to speed the flow of coolant), recheck the level of the coolant reservoir and add coolant if necessary. NEVER remove the radiator cap when the engine is still warm.
To create more working room, it is also optional to remove the passenger side motor mount. You can also remove the power steering reservoir to move the hose out of the way. As was previously mentioned, you can also remove the power steering belt. Lastly, it is also possible that removing the crank pulley will also create more working room. All these require a little more time but may be worth it if you need the extra room ie. big hands, etc.