Nissan Sentra B18 (2020-2025) Service Manual: Cylinder Head

Exploded View

Exploded View

REMOVAL

1.	Cylinder head assembly	2.	Cylinder head bolt	3.	Cylinder head gasket
A.	Refer to Removal and Installation.

DISASSEMBLY

1.	Valve collet	2.	Valve spring retainer	3.	Valve spring (EXH)
4.	Valve oil seal	5.	Valve guide (EXH)	6.	Valve seat (EXH)
7.	Valve (EXH)	8.	Valve (INT)	9.	Valve seat (INT)
10.	Cylinder head	11.	Valve guide (INT)	12.	Spark plug
13.	Valve spring (INT)	A.	Refer to Disassembly and Assembly.

Removal and Installation

Removal and Installation

REMOVAL

Remove the camshafts. Refer to Removal and Installation.

Remove the EGR inlet tube heat shield. Refer to Exploded View.

Remove the bolts securing the EGR inlet tube to the exhaust manifold. Refer to Exploded View.

Disconnect the harness connector from the air fuel ratio (A/F) sensor 1.

Disengage the air fuel ratio (A/F) sensor 1 harness from the harness retainer on the exhaust manifold cover.

Remove exhaust manifold cover. Refer to Exploded View.

Remove exhaust manifold stay. Refer to Exploded View.

Loosen exhaust manifold nuts in reverse of the sequence shown and remove exhaust manifold.

CAUTION:

Do not reuse exhaust manifold nuts.

Remove exhaust manifold gasket.

CAUTION:

• Cover engine openings to avoid entry of foreign materials.

• Do not reuse exhaust manifold gasket.

Remove the high pressure fuel rail insulator. Refer to Exploded View.

Disconnect the harness connector from the fuel rail pressure sensor.

Loosen high pressure fuel rail nuts and bolts in reverse of the sequence shown and remove the high pressure fuel rail.

CAUTION:

• When removing, be careful to avoid any interference with fuel injector.

• Use a shop cloth to absorb any fuel that leaks from high pressure fuel rail.

If fuel injectors remain in cylinder head after removing high pressure fuel rail, remove the fuel injectors using the following procedure:

CAUTION:

• Be careful with remaining fuel that may go out from high pressure fuel rail.

• Be careful not to damage injector nozzles during removal.

• Do not bump or drop fuel injector.

• Do not disassemble fuel injector.

Spray a suitable lubricant around fuel injector bore (A). Rotate fuel injector assembly (1) back and forth to allow suitable lubricant to seep into bore. Pull straight out on fuel injector assembly to remove from cylinder head.

Remove O-ring, backup ring and injector holder from fuel injector. Refer to Exploded View.

CAUTION:

Do not reuse O-ring, backup ring or injector holder.

Cut seal ring (1) while pinching it.

CAUTION:

• Do not scratch fuel injector when removing seal ring.

• Do not reuse seal ring.

Disconnect the harness connector from the engine coolant temperature sensor. Refer to Exploded View.

Remove the water hoses from the EGR cooler. Refer to Exploded View.

Remove bolts and remove the EGR cooler (if necessary). Refer to Exploded View.

CAUTION:

Do not reuse EGR cooler gasket.

Remove bolts and remove the EGR cooler bracket (if necessary). Refer to Exploded View.

Remove the bolt and remove the ground cable from the cylinder head.

Remove the water outlet (if necessary). Refer to Exploded View.

Loosen cylinder head bolts in reverse of the sequence shown and remove the cylinder head.

: Engine front

Remove cylinder head gasket.

CAUTION:

Do not reuse cylinder head gasket.

INSTALLATION

Install cylinder head gasket.

CAUTION:

Do not reuse cylinder head gasket.

Install cylinder head and tighten cylinder head bolts using the following procedure:

CAUTION:

If cylinder head bolts are reused, check their outer diameters before installation. Refer to Inspection.

Tighten all cylinder head bolts to the specified torque in the sequence shown.

Cylinder head bolts

: 40 N·m (4.1 kg-m, 30 ft-lb)

: Engine front

Tighten cylinder head bolts to the specified angle in the sequence shown.

CAUTION:

Check and confirm the tightening angle by using a Tool (A) or protractor. Do not judge by visual inspection without the Tool.

Tool number (A)

: KV10112100 (BT-8653-A)

Tightening angle

: 100°

Tighten cylinder head bolts to the specified angle in the sequence shown.

CAUTION:

Check and confirm the tightening angle by using a Tool (A) or protractor. Do not judge by visual inspection without the Tool.

Tool number (A)

: KV10112100 (BT-8653-A)

Tightening angle

: 100°

Install seal ring to fuel injector using the following procedure:

CAUTION:

• Handle seal ring with bare hands. Do not wear gloves.

• Do not apply engine oil to seal ring.

• Do not clean seal ring with solvent.

Install Tool (A) to fuel injector (1).

Tool number (A)

: KV10119720 (NI-50364)

Set seal ring (1) into Tool (A).

Tool number (A)

: KV10119730 (NI-50364)

Straightly insert seal ring (1), which is set in step b, to fuel injector as shown and install onto fuel injector.

CAUTION:

Be careful that seal ring does not exceed the groove portion of fuel injector.

Insert Tool (A) to fuel injector and rotate clockwise and counterclockwise by 90° while pressing seal ring to fit it. Note:

This is done to correct any elongation of the seal ring caused by installation and for preventing sticking when inserting fuel injector into cylinder head.

Tool number (A)

: KV10119710 (NI-50364)

Install O-ring and backup ring to fuel injector.

CAUTION:

• Do not reuse O-ring.

• Handle O-ring with bare hands. Do not wear gloves.

• Lubricate O-ring with new engine oil.

• Do not clean O-ring with solvent.

• Check that O-ring and its mating part are free of foreign material.

• When installing O-ring , be careful not to scratch it with tool or fingernails. Also be careful not to twist or stretch O-ring . If O-ring was stretched while it was being attached, do not insert it quickly into high pressure fuel rail.

• Insert new O-ring straight into high pressure fuel rail. Do not decenter or twist it.

• Always install the back up ring (1) in the right direction as instructed.

  

Install the fuel injectors to the high pressure fuel rail using the following procedure: Install the injector holder (1) onto the fuel injector (2).

CAUTION:

• Do not reuse injector holder.

• Be careful to keep injector holder from interfering with O-ring. If interference occurs, replace O-ring.

Insert fuel injector into high pressure fuel rail with injector holder attached.

• Insert it while matching it to the axial center.

• Insert so that tab (B) of injector holder is aligned to cutout (A) of high pressure fuel rail.

  

Check that installation is complete by checking that fuel injector does not rotate or come off.

Install high pressure fuel rail and fuel injector assembly to cylinder head and tighten nuts and bolts to the specified torque in the sequence shown.

Step 1	: 10.0 N·m (1.0 kg-m, 89 in-lb)
Step 2	: 25 N·m (2.6 kg-m, 18 ft-lb)

Install exhaust manifold gasket to cylinder head.

CAUTION:

Do not reuse exhaust manifold gasket.

Install exhaust manifold and tighten exhaust manifold nuts to the specified torque in the sequence shown.

CAUTION:

Do not reuse exhaust manifold nuts.

Note:

Repeat tightening sequence to ensure exhaust manifold nuts are tightened to the specified torque.

Exhaust manifold nuts

: 33.4 N·m (3.4 kg-m, 25 ft-lb)

Installation of the remaining components is in the reverse order of removal.

Disassembly and Assembly

Disassembly and Assembly

DISASSEMBLY

Remove spark plug with Tool.

Tool number

: — (NI-48891)

Remove valve lifter.

• Identify installation positions, and store them without mixing them up.

Compress the valve spring with suitable tool (A/B/C) and remove the valve collet with a suitable magnetic tool.

CAUTION:

• Be careful not to damage valve lifter holes.

• The center of the suitable tool (A) and valve spring retainer (1) must be aligned.

  

Remove valve spring retainer and valve spring (with valve spring seat).

CAUTION:

Do not remove valve spring seat from valve spring.

Push valve into combustion chamber side and remove valve.

• Identify installation positions, and store them without mixing them up.

Remove valve oil seal with suitable tool (A).

When valve seat must be replaced.

• Bore out old valve seat until it collapses. Boring should not continue beyond the bottom face of the valve seat recess in cylinder head. Set the machine depth stop to ensure this. Refer to Cylinder Head.

  CAUTION:

  Do not bore excessively to prevent cylinder head from being damaged.

Drive out valve guide with a hammer and suitable tool (A).

ASSEMBLY

When valve guide is removed, install it.

CAUTION:

Replace with oversize [0.2 mm (0.008 in)] valve guide.

Ream cylinder head valve guide hole with a suitable tool (A).

For service parts: Oversize [0.2 mm (0.008 in)]

Refer to Cylinder Head.

Press valve guide (1) from camshaft side to dimensions as shown.

Projection (H)

: Refer to Cylinder Head.

(2)	: Cylinder head

Apply reamer finish to valve guide with a suitable tool (A).

Standard

: Refer to Cylinder Head.

When valve seat is removed, install it.

CAUTION:

Replace with oversize [0.5 mm (0.020 in)] valve seat.

Ream cylinder head (1) recess diameter for service valve seat (2).

For service parts: Oversize [0.5 mm (0.020 in)]

Refer to Cylinder Head.

• Be sure to ream in circles concentric to the valve guide center.

  This will enable valve seat to fit correctly.

Press-fit valve seat into cylinder head. Using suitable tool (A), finish valve seat to the specified dimensions. For dimensions, refer to Cylinder Head.

CAUTION:

When using suitable tool, firmly grip the suitable tool handle with both hands. Then, press on the contacting surface all around the circumference to cut in a single drive. Improper pressure on with the cutter or cutting many different times may result in stage valve seat.

Using compound, grind to adjust valve fitting. Check again for normal contact. Refer to Inspection.

Install valve oil seal using suitable tool (A) to the specified height (H). Note:

Dimension is height that measured before installing valve spring (with valve spring seat).

Height (H)

: 15.1 - 15.7 mm (0.594 - 0.618 in)

Install valve.

• Install larger diameter to intake side.

Install valve spring (with valve spring seat).

• Install smaller pitch (valve spring seat side) to cylinder head side (B).

  

  CAUTION:

  Do not remove valve spring seat (C) from valve spring.

• Confirm identification color (A) of valve spring.

  Intake	: Yellow
  Exhaust	: None

Install valve spring retainer.

Install valve collet.

• Compress the valve spring with suitable tool (A/B/C) and install the valve collet with a suitable magnetic tool.

  

  CAUTION:

  • Be careful not to damage valve lifter holes.

  • The center of the suitable tool (A) and valve spring retainer (1) must be aligned.

    

• Tap valve stem edge lightly with a plastic hammer after installation to check its installed condition.

Install valve lifter.

• Install it in the original position.

Install spark plug with Tool.

Tool number

: — (NI-48891)

Inspection

Inspection

INSPECTION AFTER REMOVAL

Cylinder Head Bolts Outer Diameter

• Cylinder head bolts are tightened by plastic zone tightening method. Whenever the size difference between (A) and (B) exceeds the limit, replace them with a new one.

  

  Limit [(A) – (B)]	: 0.15 mm (0.0059 in)
  Dimension (C)	: 45 mm (1.77 in)
  Dimension (D)	: 11 mm (0.43 in)

• If reduction of outer diameter appears in a position other than (B), use it as (B) point.

Cylinder Head Distortion

Note:

When performing this inspection, cylinder block distortion should be also checked. Refer to Inspection.

Wipe off engine oil and remove water scale (like deposit), gasket, sealant, carbon, etc. with a suitable tool.

CAUTION:

Do not allow gasket debris to enter passages for engine oil or water.

At each of several locations on bottom surface of cylinder head, measure the distortion in six directions using suitable tool (A) and suitable tool (B).

Limit

: Refer to Cylinder Head.

• If it exceeds the limit, replace cylinder head.

INSPECTION AFTER DISASSEMBLY

VALVE DIMENSIONS

• Check the dimensions of each valve. For the dimensions, refer to Cylinder Head.

• If dimensions are out of the standard, replace valve and check valve seat contact. Refer to "VALVE SEAT CONTACT".

VALVE GUIDE CLEARANCE

Valve Stem Diameter

• Measure the diameter of valve stem with a suitable tool (B).

  

  Standard

  : Refer to Cylinder Head.

Valve Guide Inner Diameter

• Measure the inner diameter of valve guide with a suitable tool (A).

  Standard

  : Refer to Cylinder Head.

Valve Guide Clearance

• (Valve guide clearance) = (Valve guide inner diameter) – (Valve stem diameter)

  Standard and Limit

  : Refer to Cylinder Head.

• If the calculated value exceeds the limit, replace valve and/or valve guide. When valve guide must be replaced. Refer to Disassembly and Assembly.

VALVE SEAT CONTACT

• After confirming that the dimensions of valve guides and valves are within the specifications, perform this procedure.

• Apply prussian blue (or white lead) onto contacting surface of valve seat to check the condition of the valve contact on the surface.

• Check if the contact area band is continuous all around the circumference.

  

  (A)

  : OK

• If not, grind to adjust valve fitting and check again. If the contacting surface still has “NG” conditions (B) even after the recheck, replace valve seat. Refer to Disassembly and Assembly.

VALVE SPRING SQUARENESS

• Set a suitable tool (D) along the side of valve spring and rotate spring. Measure the maximum clearance (A) between the top of spring and suitable tool.

  

  (B)	: Suitable tool
  (C)	: Contact area

  Limit

  : Refer to Cylinder Head.

• If it exceeds the limit, replace valve spring.

VALVE SPRING DIMENSIONS AND VALVE SPRING PRESSURE LOAD

• Check valve spring pressure (A) with valve spring seat installed at the specified spring height.

  

  CAUTION:

  Do not remove valve spring seat from valve spring.

  Note:

  Before measuring valve spring pressure, compress each spring to specified solid height for intake and exhaust valve springs.

  Valve spring (EXH)	: 28.4 mm (1.118 in)
  Valve spring (INT)	: 26.77 mm (1.0539 in)

  Standard

  : Refer to Cylinder Head.

• If the installation load or load with valve open is out of the standard, replace valve spring (with valve spring seat).

INSPECTION AFTER INSTALLATION

Inspection for Leakage

The following are procedures for checking fluids leakage, lubricates leakage, and exhaust gases leakage.

• Before starting engine, check oil/fluid levels including engine coolant and engine oil. If less than required quantity, fill to the specified level. Refer to Fluids and Lubricants.

• Use procedure below to check for fuel leakage.

  • Place ignition switch in the “ON” position (with engine stopped). With fuel pressure applied to fuel piping, check for fuel leakage at connection points.

  • Start engine. With engine speed increased, check again for fuel leakage at connection points.

• Run engine to check for unusual noise and vibration.

  Note:

  If hydraulic pressure inside timing chain tensioner drops after removal/installation, slack in guide may generate a pounding noise during and just after the engine start. However, this does not indicate an unusualness. Noise will stop after hydraulic pressure rises.

• Warm up engine thoroughly to check there is no leakage of fuel, or any oil/fluids including engine oil and engine coolant.

• Bleed air from lines and hoses of applicable lines, such as in cooling system.

• After cooling down engine, again check oil/fluid levels including engine oil and engine coolant. Refill to the specified level, if necessary.

  Summary of the inspection items:

  Items		Before starting engine	Engine running	After engine stopped
  Engine coolant		Level	Leakage	Level
  Engine oil		Level	Leakage	Level
  Transmission / transaxle fluid	AT & CVT Models	Leakage	Level / Leakage	Leakage
  	MT Models	Level / Leakage	Leakage	Level / Leakage
  Other oils and fluids*		Level	Leakage	Level
  Fuel		Leakage	Leakage	Leakage
  Exhaust gases		—	Leakage	—

  *: Power steering fluid, brake fluid, etc.