How to replace the cross over tube on heads

If you have antifreeze leaking from what appears to be coming from the transmission bell housing, the leak is most likely (although possible) not at the rear of the engine.

There COULD be a freeze plug at the back side of the engine between the engine and transmission leaking. However, on the 4.6L engines, it is most commonly caused by either a water pump, heater hose, or intake manifold leaking at the FRONT of the engine.

Leaks in these areas will fill the area between the cylinder heads with coolant, which will run to the back of the engine and out the hole in the cylinder block that is located just above the transmission bell housing. This makes it LOOK like the leak is in the rear.

To verify this condition use a flashlight to look under the intake manifold just past the alternator. Sometimes it is also very helpful to remove the serpentine belt and remove the alternator (very easy to do) to verify that this is the problem.

Take a hard look at the coolant cross-over pipe on the front of the intake manifold assembly. These are notorious for leaking on both sides and VERY LIKELY to be leaking on the driver's side where the thermostat is located.

This problem is so common that an aftermarket company named DORMAN has come up with an aftermarket replacement intake manifold to correct the problem. The DORMAN part number for your vehicle is Part Number: 615-175 It is available at many aftermarket parts suppliers including AutoZone, O'Reilly's, and Advance, for around $230 (USD). (See picture below)

The easiest way to make a "temporary" fix is to remove the hose from one of the heater tubes, then cut the other hose so that it is long enough to reach the tube that has the hose removed. Attach the hose from one tube to the other to form a "loop" so the coolant will simply circulate from one tube to the other while bypassing the offending hose in the rear. I cannot tell you exactly WHERE to perform this operation without being able to SEE the vehicle, but it is usually easiest to do this in the engine compartment as close to the engine as possible.

If you are only going to go get it repaired, it may be worth the cost of towing. Cutting the hoses may cause you to have to replace more parts and will involve more labor for the final repair. Depending on your insurance coverage, you MIGHT be able to get reimbursed for the tow. However, you cannot get reimbused for a cut hose. I recommend that you weigh the options before doing anything.

Yes, there are expansion plugs (freeze plugs) on both sides of the engine block and at the rear of the engine block between the engine and transmission. There are also a couple in the ends of the cylinder heads.

With all that said, I would like to add that many times with that engine, the heater tube and connecting hoses can leak and be mistaken for a rear expansion plug leaking. I would definately check this before pulling the transmission out.

There is a tube that runs from the back of the water pump under the intake manifold and out the rear of the engine where it hooks up to the heater hose/heater core. This tube has a small hose connecting it to the back of the water pump. There is also a hole in the back of the engine block that will allow antifreeze from under the intake manifold to leak into the transmission bell housing area. When this tube or hose leaks, it often gets mistaken for a leaking rear expansion plug.

It is very easy to check for this. Remove the serpentine belt and remove the alternator and look under the intake manifold down in the "valley" between the cylinder heads. If there is antifreeze in there, the hose or the tube is leaking. Look at the picture below. Item #3 is the tube and hose assembly I am talking about. Usually, just the hose is leaking. It should be replaced with a short piece of SILICONE heater hose. On some of the vehicles, there are 2 hose clamps. On others, the end of the hose that is attached to the tube has a crimped collar on it. If yours is like this, you can fix it by carefully cutting the crimp collar off and replacing the hose using band clamps. (screw-type)

Also look for antifreeze leaking into this area from the front intake manifold runner. They tend to leak on the front runner near where the thermostat housing is located. These will also leak into the valley area and run out the back of the engine. If the manifold is leaking, chances are it is warped. DORMAN makes a replacement intake manifold kit just for this purpose because it has been so common. It is also very easy to check for this with the alternator removed.
The DORMAN part number for your vehicle is 615-178 (See second picture below)

Depends where it is leaking. If it is leaking on top of the transmission bell housing it is probably the o ring on the back of the thermostat housing. (there is a rather large tube that carries coolant from the water pump on the other side of the engine to the t stat housing.) If the leak is passenger side it could be the water pump or the o ring on the other side of the earlier mentioned tube ( the tube runs under the intake manifold in the V of the engine). Other areas it could be the heater hoses or the upper or lower radiator hoses. Also a bad head gasket will do it also, signs of that can be water in your oil ( oil that is tan in color is a sign of moisture ) but you still can have a blown head gasket without water in the oil. A leaking heater core can also be a problem (wet area on the passenger side floor can be a sign of this) Also a worn radiator cap can leak into the overflow bottle and out on the ground. A sign of this is a over flow bottle that is completely full inspect the rubber seal an the cap or just replace it. The t stat housing problem is unique to the 2.5 v6 and the housing is tricky to remove. I described this procedure on wiki answer. Google - Thermostat housing 2.5 v6 water pipe 1996 and you will find it the instructions apply actually to a 1999 but is similar for most chrysler 2.5 v6's

CYLINDER HEAD REMOVAL

2.5L Engines

1. Before servicing the vehicle, refer to the Precautions Section.
   
2. Drain cooling system and engine oil.
   
3. Relieve the fuel system pressure.
   
4. Remove or disconnect the following:
   
   • Negative battery cable
     
   • Upper radiator hose and heater hose
     
   • Right side fuse/relay box and move aside
     
   • Engine undercover
     
   • Resonator and air cleaner case
     
   • Engine top cover
     
   • All electrical and vacuum lines at the head
     
   • Fuse hose quick connector at fuel tube side
     
   • Engine harness and power steering hose bracket
     
   • Timing chain
     
   • Drive belt tensioner
     
   • Camshafts
     
   • Spark plugs
     
   • Exhaust manifold
     
5. Support the engine from above and below with a suitable jack and hoist.
   
6. Remove or disconnect the following:
   
   • Power steering pump and reservoir and wire aside
     
   • Auxiliary drive belts
     
   • A/C compressor and wire aside
     
   • Upper sway bar links
     
   • Front and rear engine mount through bolts
     
   • Lower ball joints
     
   • 2 steering gear housing mounting bolts
     
   • Front suspension member bolts and front suspension member
     
7. Loosen the cylinder head bolts in the sequence shown and remove the cylinder head.
   

Removing the front suspension member—Altima


Cylinder head bolt removal sequence—2.5L engine–Altima and Sentra


Cylinder head bolt tightening sequence—2.5L engine–Altima and Sentra

To install:

1. Clean the gasket surfaces.
   
2. Using new head gaskets, install the cylinder heads.
   NOTE If possible, replacement of the head bolts is suggested.
   
   
3. If replacement of the head bolts is not possible, perform the following bolt measurement:
   
   • Measure the diameter of the head bolt 0.43 in. (11mm) from the bottom of the bolt.
     
   • Measure the diameter of the head bolt 2.17 in. (55mm) from the bottom of the bolt.
     
   • Whenever the size difference between the 2 measurements exceeds 0.0091 in. (0.23mm) the head bolts must be replaced.
     
4. Apply clean engine oil to the bolt threads and seating surfaces and tighten the cylinder head bolts in sequence as follows:
   
   • Step 1: 72 ft. lbs. (98 Nm).
     
   • Step 2: Loosen all the bolts completely.
     
   • Step 2: 29 ft. lbs. (33 Nm).
     
   • Step 4: Plus 75–80 degrees clockwise.
     
   • Step 5: Plus 75–80 degrees clockwise.
     
5. Install the front suspension member and tighten the bolts to the specifications shown in the illustration.
   
6. Install or connect the following:
   
   • 2 steering gear housing mounting bolts
     
   • Lower ball joints
     
   • Front and rear engine mount through bolts
     
   • Upper sway bar links
     
   • A/C compressor
     
   • Auxiliary drive belts
     
   • Power steering pump and reservoir
     
   • Exhaust manifold
     
   • Spark plugs
     
   • Camshafts
     
   • Drive belt tensioner
     
   • Timing chain
     
   • Engine harness and power steering hose bracket
     
   • Fuse hose quick connector at fuel tube side
     
   • All electrical and vacuum lines at the head
     
   • Engine top cover
     
   • Resonator and air cleaner case
     
   • Engine undercover
     
   • Right side fuse/relay box and move aside
     
   • Upper radiator hose and heater hose
     
   • Negative battery cable
     
7. Fill the cooling system and engine oil
   
8. Start the vehicle, check for leaks and repair if necessary.
   

most likely it is the valve cover gasket. it covers the valve train where there is alot of oil to lube the top of the motor. if the head gasket was leaking it may have more signs of running poorly. also having coolant leaks also. so i will have to say valve cover gasket. now usally you may have a oil burning smell with it depending on the area of the lek but not always.

the valve cover can easily be seen when the hood is open. it is right on the top and where it meets the clyinder head is where the gasket is and the leak can be seen.

if you have more question please ask.

The evaporator coil is located in the heater-A/C housing, under the instrument panel.

The heater-A/C housing assembly must be removed from the vehicle and the two halves of the housing separated for service access of the heater core, evaporator coil, blend-air door, and each of the various mode control doors.

WARNING: On vehicles equipped with airbags, refer to Airbag Systems Safety Information and Procedures. Before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Failure to take the proper precautions could result in accidental airbag deployment and possible personal injury. See: Restraint SystemsAir Bag SystemsService Precautions

REMOVAL

1. Disconnect and isolate the battery negative cable.
2. Remove the instrument panel from the vehicle.
3. If the vehicle is not equipped with air conditioning, go to Step 6. If the vehicle is equipped with air conditioning, recover the refrigerant from the refrigerant system.
4. Disconnect the liquid line refrigerant line fitting from the evaporator inlet tube.

• Install plugs in, or tape over all of the opened refrigerant line fittings.

1. Disconnect the accumulator inlet tube refrigerant line fitting from the evaporator outlet tube. See Refrigerant Line Coupler for the procedures.

• Install plugs in, or tape over all of the opened refrigerant line fittings.

1. Drain the engine cooling system.
2. Disconnect the heater hoses from the heater core tubes. Install plugs in, or tape over the opened heater core tubes.
3. Unplug the heater-A/C system vacuum supply line connector from the tee fitting near the heater core tubes.

Unplug the heater-A/C unit wire harness connector, which is fastened to the heater-A/C housing next to the blower motor relay.

1. Remove the five nuts from the heater-A/C housing mounting studs on the engine compartment side of the dash panel. Remove or reposition the evaporation canister for additional access, if required.
2. Pull the heater-A/C housing rearward far enough for the mounting studs and the evaporator condensate drain tube to clear the dash panel holes.
3. Remove the heater-A/C housing from the vehicle.

INSTALLATION

1. Position the heater-A/C housing to the dash panel. Be certain that the evaporator condensate drain tube and the housing mounting studs are inserted into their correct mounting holes.
2. Install and tighten the five nuts onto the heater-A/C housing mounting studs on the engine compartment side of the dash panel. Tighten the nuts to 6.2 Nm (55 in. lbs.) .
3. If the evaporation canister was repositioned during the removal procedure, reinstall it to its proper position.
4. Connect the Heater-A/C system vacuum supply line connector to the tee fitting near the heater core tubes.
5. Unplug or remove the tape from the heater core tubes. Connect the heater hoses to the heater core tubes and fill the engine cooling system.
6. If the vehicle is not equipped with air conditioning, go to Step 10. If the vehicle is equipped with air conditioning, unplug or remove the tape from the accumulator inlet tube and the evaporator outlet tube fittings. Connect the accumulator inlet tube coupler to the evaporator outlet tube.
7. Unplug or remove the tape from the liquid line and the evaporator inlet tube fittings. Connect the liquid line coupler to the evaporator inlet tube.
8. Evacuate the refrigerant system.
9. Charge the refrigerant system.
10. Install the instrument panel in the vehicle.
11. Connect the battery negative cable.
12. Start the engine and check for proper operation of the heating and air conditioning systems.

If you just want to change the seal at the fuel lines, you may be able to if you have enough patience and a few specially bent wrenches. It is much easier to remove the turbo. If you do remove the turbo don't forget to replace the two o-rings. If you want to remove the pump completly (most of the time a new pump is needed to repair a leak), then I would remove the fuel supply tube bolt from the back of the pump, remove the fuel lines from both heads, replacing the grommets with the updated grommet which resist breaking apart from the newer fuels. Then remove the two bolts from the pump and rotate the engine by hand untill the pump comes up about a half inch. This way if the tappet falls out of the pump the cam lobe will be up enough that it will not fall down into the engine. Then you can replace the o-ring at the bottem of the pump and all the rest of the seals or the entire pump. Don't forget when going back together seat the pump and then rotate the engine by hand again untill the pump sits almost flush and then torque everything. The fuel supply tube should be about 40 ft. lbs. The bolts are probably around 120 inch lbs like everything else but just use good judgement. You can make a clicking sound while using a regular ratchet if it makes you feel better.

REMOVAL

WARNING:

• ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN AN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.
• REVIEW THE WARNINGS AND CAUTIONS IN THE FRONT OF THIS SECTION BEFORE PERFORMING THE FOLLOWING OPERATION. See: Heating and Air Conditioning\Service Precautions

1. Remove the HVAC housing from the vehicle. See: Heating and Air Conditioning\Housing Assembly HVAC\Service and Repair
2. Remove the foam gasket surrounding the core tubes. NOTE: Notice the orientation of the irregularly shaped gasket on the tubes. The gasket must be placed correctly to ensure proper sealing against the body during reinstallation
   1. Remove the screws and retainers that secure the heater core and tubes to the HVAC housing.
   2. Remove the mode door actuator if necessary for clearance to remove the core.
      1. Lift the heater core straight up and out of the HVAC housing.
      2. When replacing individual tubes, loosen and remove the round tube-to-core clamp, and pull tube from core.
      INSTALLATION
      
      WARNING: REVIEW THE WARNINGS AND CAUTIONS IN THE FRONT OF THIS SECTION BEFORE PERFORMING THE FOLLOWING OPERATION. See: Heating and Air Conditioning\Service Precautions
      
      Any kinks or sharp bends in the refrigerant plumbing will reduce the capacity of the entire air conditioning system. Kinks and sharp bends reduce the flow of refrigerant in the system. A good rule for the flexible hose refrigerant lines is to keep the radius of all bends at least ten times the diameter of the hose. In addition, the flexible hose refrigerant lines should be routed so they are at least 80 millimeters (3 inches) from the exhaust manifold.
      
      High pressures are produced in the refrigerant system when the air conditioning compressor is operating. Extreme care must be exercised to make sure that each of the refrigerant system connections is pressure-tight and leak free. It is a good practice to inspect all flexible hose refrigerant lines at least once a year to make sure they are in good condition and properly routed.
      
      
      
      1. When installing individual tubes, insert tube into core ensuring that tube O-ring is seated in core and not pinched. Hold tube in seated position while installing the round tube-to-core clamp. NOTE: The round tube-to-heater-core clamp should be left loose enough to turn the tube in the core. Position the core in the housing, and then tighten the tube-to-heater-core clamp after orienting the tubes to the molded HVAC housing.
      2. Lower the heater core into the HVAC housing.
      3. Install the mode door actuator, if removed from housing for core removal.
      4. Position the retainers over the heater core tubes. Install and tighten the screws that secure the heater core and retainers to the HVAC housing. Tighten the screws to 2.2 Nm (20 in. lbs.) . NOTE: The grounding strap is to be attached to the lower heater core tube retainer.
      5. Reinstall the HVAC housing to the vehicle. See: Heating and Air Conditioning\Housing Assembly HVAC\Service and Repair

1. Position the HVAC housing to the dash panel. Be certain that the evaporator condensate drain tube and the housing mounting studs are inserted into their correct mounting holes.
2. Install the HVAC housing mounting nuts to the studs on the passenger compartment side of the dash panel. Tighten the nuts to 4.5 Nm (40 in. lbs.) .
3. Connect the HVAC housing wire harness connectors.
4. Reinstall the rear floor heat ducts to the center floor heat duct outlets.
5. Install and tighten the nuts onto the HVAC housing mounting studs on the engine compartment side of the dash panel. Tighten the nuts to 7 Nm (60 in. lbs.) .
6. Reinstall the PCM to the passenger side dash panel in the engine compartment. See: Powertrain Management\Computers and Control Systems\Engine Control Module\Service and Repair
7. Reinstall the coolant reserve/overflow bottle to the passenger side inner fender shield. See: Engine, Cooling and Exhaust\Cooling System\Coolant Reservoir
8. If the vehicle is equipped with the manual temperature control system, connect the HVAC system vacuum supply line connector to the tee fitting near the heater core tubes.
9. Unclamp/unplug the heater core hoses and tubes. Connect the heater hoses to the heater core tubes and fill the engine cooling system. See: Engine, Cooling and Exhaust\Cooling System\Service and Repair
10. Unplug or remove the tape from the suction line and the evaporator outlet tube fittings. Connect the suction line to the evaporator outlet tube. Tighten retaining nut to 28 Nm (250 in. lbs.) .
11. Unplug or remove the tape from the liquid line and the evaporator inlet tube fittings. Connect the liquid line to the evaporator inlet tube. Tighten retaining nut to 28 Nm (250 in. lbs.) .
12. Evacuate the refrigerant system. See: Refrigerant\Service and Repair
13. Charge the refrigerant system. See: Refrigerant\Service and Repair
14. Install the instrument panel in the vehicle. Refer to: Body and Frame, Interior Trim, Dashboard/Instrument Panel, Service and Repair, Instrument Panel Service Procedures, Instrument Panel Assembly Replacement, See: Body and Frame\Interior Moulding / Trim\Dashboard / Instrument Panel\Service and Repair\Procedures\Instrument Panel Assembly Replacement
15. Connect the battery negative cable.
16. Start the engine and check for proper operation of the heating and air conditioning systems.
    

The heater-A/C housing assembly must be removed from the vehicle and the two halves of the housing separated for service access of the heater core, evaporator coil, blend-air door, and each of the various mode control doors.

WARNING: On vehicles equipped with airbags, refer to Airbag Systems Safety Information and Procedures. Before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Failure to take the proper precautions could result in accidental airbag deployment and possible personal injury. See: Restraint Systems\Air Bag Systems\Service Precautions

REMOVAL

1. Disconnect and isolate the battery negative cable.
2. Remove the instrument panel from the vehicle. Refer to: Body and Frame, Interior Trim, Dashboard / Instrument Panel, Service and Repair, Instrument Panel Service Procedures, Instrument Panel Assembly Replacement, See: Body and Frame\Interior Moulding / Trim\Dashboard / Instrument Panel\Service and Repair\Instrument Panel Assembly
3. If the vehicle is not equipped with air conditioning, go to Step 6. If the vehicle is equipped with air conditioning, recover the refrigerant from the refrigerant system. Refer to: Heating and Air Conditioning, Service and Repair, Procedures, Refrigerant System Recovery, See: Service and Repair\Refrigerant System Recovery
4. Disconnect the liquid line refrigerant line fitting from the evaporator inlet tube.

• Install plugs in, or tape over all of the opened refrigerant line fittings.

1. Disconnect the accumulator inlet tube refrigerant line fitting from the evaporator outlet tube. See Refrigerant Line Coupler for the procedures.

• Install plugs in, or tape over all of the opened refrigerant line fittings.

1. Drain the engine cooling system.
2. Disconnect the heater hoses from the heater core tubes. Install plugs in, or tape over the opened heater core tubes.
3. Unplug the heater-A/C system vacuum supply line connector from the tee fitting near the heater core tubes.
4. Unplug the heater-A/C unit wire harness connector, which is fastened to the heater-A/C housing next to the blower motor relay.
   1. Remove the five nuts from the heater-A/C housing mounting studs on the engine compartment side of the dash panel. Remove or reposition the evaporation canister for additional access, if required.
   2. Pull the heater-A/C housing rearward far enough for the mounting studs and the evaporator condensate drain tube to clear the dash panel holes.
   3. Remove the heater-A/C housing from the vehicle.
   INSTALLATION
   
   1. Position the heater-A/C housing to the dash panel. Be certain that the evaporator condensate drain tube and the housing mounting studs are inserted into their correct mounting holes.
   2. Install and tighten the five nuts onto the heater-A/C housing mounting studs on the engine compartment side of the dash panel. Tighten the nuts to 6.2 Nm (55 in. lbs.) .
   3. If the evaporation canister was repositioned during the removal procedure, reinstall it to its proper position.
   4. Connect the Heater-A/C system vacuum supply line connector to the tee fitting near the heater core tubes.
   5. Unplug or remove the tape from the heater core tubes. Connect the heater hoses to the heater core tubes and fill the engine cooling system.
   6. If the vehicle is not equipped with air conditioning, go to Step 10. If the vehicle is equipped with air conditioning, unplug or remove the tape from the accumulator inlet tube and the evaporator outlet tube fittings. Connect the accumulator inlet tube coupler to the evaporator outlet tube.
   7. Unplug or remove the tape from the liquid line and the evaporator inlet tube fittings. Connect the liquid line coupler to the evaporator inlet tube.
   8. Evacuate the refrigerant system. Refer to: Heating and Air Conditioning, Service and Repair, Procedures, Refrigerant System Evacuate, See: Service and Repair\Refrigerant System Evacuate
   9. Charge the refrigerant system. Refer to: Heating and Air Conditioning, Service and Repair, Procedures, Refrigerant System Charge, See: Service and Repair\Refrigerant System Charge
   10. Install the instrument panel in the vehicle. Refer to: Body and Frame, Interior Trim, Dashboard / Instrument Panel, Service and Repair, Instrument Panel Service Procedures, Instrument Panel Assembly Replacement, See: Body and Frame\Interior Moulding / Trim\Dashboard / Instrument Panel\Service and Repair\Instrument Panel Assembly
   11. Connect the battery negative cable.
   12. Start the engine and check for proper operation of the heating and air conditioning systems.

REMOVAL AND INSTALLATION

WARNING: On vehicles equipped with airbags, refer to Airbag Systems Safety Information and Procedures. Before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Failure to take the proper precautions could result in accidental airbag deployment and possible personal injury. See: Restraint Systems\Air Bag Systems\Service Precautions

1. Remove and disassemble the heater-A/C housing. Refer to: Heating and Air Conditioning, Housing Assembly HVAC, Service and Repair, See: Heating and Air Conditioning\Housing Assembly HVAC\Service and Repair
2. Lift the heater core out of the lower half of the heater-A/C housing.
3. Reverse the removal procedures to install. Be certain that the heater core foam insulator is reinstalled