I am replacing the water pump of my 1995 3.0 v6 infinity (same as altima) but my son removed the chain with out marking it, now I need to set the timing. How do I do this? There's marking on the valve sprockets and on the chain. Thanks

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Question edited for clarity.
Question moved to model category.

Tech Feature: Cooling System and Water Pump ...

Underhood Service https://www.underhoodservice.com > tech-feature-coo...
Here's the factory procedure for replacing the water pump on a late-model 3.5L Altima or Maxima: 1. Drain the coolant out of the cooling system by opening ...

Nissan Altima Water Pump Replacement Cost Estimate

RepairPal https://repairpal.com > estimator > water-pump-replace...
The average cost for a Nissan Altima Water Pump Replacement is between $519 and $585. · Labor costs are estimated between $154 and $195 while parts are priced ...

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It looks like your water pump on a 3.5L is run off the timing chain. I got some info which may help see it but may not be the exact as your car. If you are having some problems with overheating from what I saw looks like you have 2 thermostats and after changing thermostats, you can have air trapped in your engine, which will still allow engine to overheat.

Everything blocking the timing chain cover needs to be removed. THEN REMOVE COVER AND REMOVE OLD CHAIN making sure your cam and crank marks align. install new chain

In the 2.7L V6, the water pump is driven by the timing chain. I'm pretty sure that in the 3.2/3.5L V6, it's driven by the timing belt. In both cases, it's a lot of work to get to, as you have to remove everything on the top (intake plenum, valve covers) and front (belts, pulleys, idlers, p/s pump, and timing cover) of the engine. Then, after removing and replacing the water pump and timing chain/belt, you have to make sure that the valve timing is exactly right, and reset the chain tensioner on the 2.7L.

A lot of work. Unless you're very comfortable with working on engines, leave it to a professional. You'll save yourself a headache (not to mention some busted knuckles). ;-)

THE 2.4L AND 2.5L ENGINES.YOU HAVE TO SAFELY RAISE VECHICLE SUPPORT IT USING JACK STANDS.YOU HAVE TO REMOVE THE RIGHT HAND SPLASH SHIELD.THEN LOOSEN WATER PUMP PULLEY BOLTS LEAVE DRIVE BELT IN PLACE TO KEEP WATER PULLEY FROM TURNING WHILE LOOSEN PULLEY BOLTS.THEN YOU HAVE TO MOVE AC COMPRESSOR DONT DISCONNECT ANY REFRIGERANT LINES.JUST SET IT ASIDE THE ALTERNATOR AND ITS MOUNT ALSO HAS TO MOVED.THEN YOU ARE AT WATER PUMP.NOW THE 3.5L ENGINE WATER PUMP IS IN A TOUGH SPOT.YOU HAVE TO REMOVE ENGINE SPLASH SHIELD.REMOVE THE SUBFRAME BRACKET FROM THE RIGHT SIDE OF THE SUBFRAME ASSEMBLY. REMOVE THE INTELLIGENT POWER DISTRIBUTION MODULE ENGINE ROOM FROM THE ENGINE COMPARTMENT.REMOVE THE IPDMER UPPER COVER AND HARNESS COVER RELEASE THE TWO CLIPS.DISCONNECT THE ELECTRICAL CONNECTORS AND LIFT THE ASSEMBLY FROM THE CASE.REMOVE THE RADIATOR SHROUDS REMOVE THE DRIVE BELTS.REMOVE THE ENGINE COOLING FAN.REMOVE THE RADIATOR AND THE COOLANT RESERVOIR.REMOVE THE IDLER PULLEY AND THE POWER STEERING AND ALTERNATOR ADJUSTMENT BRACKETS.REMOVE THE FRONT ENGINE MOUNT.REMOVE COOLANT DRAIN PLUG FROM THE WATER PUMP SIDE OF THE ENGINE BLOCK.REMOVE CHAIN TENSIONER COVER AND THE WATER PUMP COVER FROM THE ENGINE FRONT COVER.REMOVE THE CHAIN TENSIONER.PULL THE LEVER DOWN TO RELEASE THE PLUNGER STOPPER TAB.INSERT A STOPPER PIN INTO THE TENSIONER BODY HOLE TO RETAIN THE LEVER IN THE RELEASED.NO CHAIN TENSION POSITION.MOVE THE PLUNGER INTO THE TENSIONER BY PRESSING THE CHAIN GUIDE AND PUSHING WITH A SCREWDRIVER.MAKE A GAP BETWEEN THE WATER PUMP GEAR AND THE TIMING CHAIN BY ROTATING THE CRANKSHAFT PULLEY 20 DEGREES COUNTERCLOCKWISE.REMOVE THE THREE WATER PUMP MOUNTING BOLTS.INSTALL 2 BOLTS SIZE M8 1.25 X 50 MM INTO THE WATER PUMP BOLT HOLES AND TIGHTEN THEM EQUALLY UNTIL THEY BOTTOM AGAINST THE CHAIN COVER.IT WILL BE NECESSARY TO ROTATE THE WATER PUMP SLIGHTLY TO ALLOW THE BOLTS TO DRIVE AGAINST THE REAR TIMING CHAIN CASE COVER INSTEAD OF THE BOLT HOLES.REMOVE THE WATER PUMP.CLEAN THE SEALANT FROM THE MATING SURFACE AND REPLACE THE O-RINGS.INSTALL THE OUTER O-RING WITH THE WHITE PAINT MARK FACING THE FRONT OF THE ENGINE AND THE INNER O-RING BLACK NEXT.APPLY A LIGHT AMOUNT OF OIL TO THE O-RINGS.TIGHTEN THE WATER PUMP BOLTS TO 62 - 89 INCH POUNDS.TIGHTEN WATER PUMP BOLTS EVENLY DONT OVER TIGHT OR YOU WILL DAMAGE WATER PUMP AND HAVE LEAKS.REINSTALL THE POWER STEERING AND ALTERNATOR ADJUSTMENT BRACKETS AND ANY OTHER COMPONENTS REMOVED FOR ACCESS TO THE WATER PUMP.REFILL THE COOLING SYSTEM.RUN THE ENGINE AND CHECK FOR LEAKS.YOU NEED TO BUY THE HAYNES REPAIR MANUAL.SO THE PHOTOS WILL HELP YOU WHEN REMOVING AND INSTALLING WATER PUMP.

no you need to replace the water pump if its leaking from the seal by the shaft or are you saying it needs a new gasket?

rubber timing belt will need removed in order to service the pump on that vehicle

line the marks on the chain to the sprokets and it should be ok, is that what we call a qx, a32 chassis seires?

A timing belt will no blow up the engine, however it will on occasion bend the valves, you will need to replace the belt and test for damage to the engine. Change the water pump and check all the pulleys while you are in there.