4.0L Engine - Service Information: Diagnosis Dodge Nitro I

CYLINDER COMBUSTION PRESSURE LEAKAGE TEST

The combustion pressure leakage test provides an accurate means for determining engine condition.

Combustion pressure leakage testing will detect

1. Exhaust and intake valve leaks (improper seating).
2. Leaks between adjacent cylinders or into water jacket.
3. Any causes for combustion/compression pressure loss.

1. Check the coolant level and fill as required. DO NOT install the pressure cap.
2. Start and operate the engine until it attains normal operating temperature, then turn the engine OFF.
3. Clean spark plug recesses with compressed air.
4. Remove the spark plugs.
5. Remove the oil filler cap.
6. Remove the air cleaner.
7. Calibrate the tester according to the manufacturer's instructions. The shop air source for testing should maintain 483 kPa (70 psi) minimum, 1,379 kPa (200 psi) maximum, with 552 kPa (80 psi) recommended.
8. Perform the test procedures on each cylinder according to the tester manufacturer's instructions. While testing, listen for pressurized air escaping through the throttle body, tailpipe and oil filler cap opening. Check for bubbles in the coolant.
9. All gauge pressure indications should be equal, with no more than 25% leakage per cylinder.
10. FOR EXAMPLE: At 552 kPa (80 psi) input pressure, a minimum of 414 kPa (60 psi) should be maintained in the cylinder.

CYLINDER COMPRESSION PRESSURE TEST

The results of a cylinder compression pressure test can be utilized to diagnose several engine malfunctions.

Ensure the battery is completely charged and the engine starter motor is in good operating condition. Otherwise the indicated compression pressures may not be valid for diagnosis purposes.

1. Check engine oil level and add oil if necessary.
2. Drive the vehicle until engine reaches normal operating temperature. Select a route free from traffic and other forms of congestion, observe all traffic laws, and accelerate through the gears several times briskly.
3. Remove all spark plugs from engine. As spark plugs are being removed, check electrodes for abnormal firing indicators fouled, hot, oily, etc. Record cylinder number of spark plug for future reference.
4. Remove the Auto Shutdown (ASD) relay from the PDC.
5. Be sure throttle blade is fully open during the compression check.
6. Insert compression gauge Adapter Special Tool 8116 or the equivalent, into the #1 spark plug hole in cylinder head. Connect the 0-500 psi (Blue) pressure transducer (Special Tool CH7059) with cable Adapters to the DRBIII®. For Special Tool identification, see «SPECIAL TOOLS»(ref-306143-S36634217892008120900000) .
7. Crank engine until maximum pressure is reached on gauge. Record this pressure as #1 cylinder pressure.
8. Repeat the previous step for all remaining cylinders.
9. Compression should not be less than 689 kPa (100 psi) and not vary more than 25 percent from cylinder to cylinder.
10. If one or more cylinders have abnormally low compression pressures, repeat the compression test.
11. If the same cylinder or cylinders repeat an abnormally low reading on the second compression test, it could indicate the existence of a problem in the cylinder in question. The recommended compression pressures are to be used only as a guide to diagnosing engine problems. An engine should not be disassembled to determine the cause of low compression unless some malfunction is present.

ENGINE OIL LEAK INSPECTION

Begin with a thorough visual inspection of the engine, particularly at the area of the suspected leak. If an oil leak source is not readily identifiable, the following steps should be followed

1. Do not clean or degrease the engine at this time because some solvents may cause rubber to swell, temporarily stopping the leak.
2. Add an oil soluble dye (use as recommended by manufacturer). Start the engine and let idle for approximately 15 minutes. Check the oil level indicator to make sure the dye is thoroughly mixed as indicated with a bright yellow color under a black light.
3. Using a black light, inspect the entire engine for fluorescent dye, particularly at the suspected area of oil leak. If the oil leak is found and identified, repair as necessary.
4. If dye is not observed, drive the vehicle at various speeds for approximately 24 km (15 miles), and repeat inspection.
5. If the oil leak source is not positively identified at this time , proceed with the AIR LEAK DETECTION TEST METHOD as follows: Disconnect the fresh air hose (make-up air) at the cylinder head cover and plug or cap the nipple on the cover. Remove the PCV valve hose from the cylinder head cover. Cap or plug the PCV valve nipple on the cover. Attach an air hose with pressure gauge and regulator to the oil level indicator tube. CAUTION: Do not subject the engine assembly to more than 20.6 kPa (3 PSI) of test pressure. Gradually apply air pressure from 1 psi to 2.5 psi maximum while applying soapy water at the suspected source. Adjust the regulator to the suitable test pressure that provides the best bubbles which will pinpoint the leak source. If the oil leak is detected and identified, repair per service information procedures. If the leakage occurs at the crankshaft rear oil seal area, refer to «INSPECTION FOR REAR SEAL AREA LEAKS»(ref-306143-S03104624482008120900000) .
6. If no leaks are detected, turn off the air supply. Remove the air hose, all plugs, and caps. Install the PCV valve and fresh air hose (make-up air). Proceed to next step.
7. Clean the oil off the suspect oil leak area using a suitable solvent. Drive the vehicle at various speeds approximately 24 km (15 miles). Inspect the engine for signs of an oil leak by using a black light.

Note. If oil leakage is observed at the oil level indicator tube to block location; remove the tube, clean and reseal using Mopar® Stud & Bearing Mount (press fit tube applications only), and for O-ring style tubes, remove tube and replace the O-ring seal.

INSPECTION FOR REAR SEAL AREA LEAKS

Since it is sometimes difficult to determine the source of an oil leak in the rear seal area of the engine, a more involved inspection is necessary. The following steps should be followed to help pinpoint the source of the leak.

If the leakage occurs at the crankshaft rear oil seal area

1. Disconnect the battery.
2. Raise the vehicle.
3. Remove torque converter or clutch housing cover and inspect rear of block for evidence of oil. Use a black light to check for the oil leak. If a leak is present in this area, remove transmission for further inspection. Circular spray pattern generally indicates seal leakage or crankshaft damage. Where leakage tends to run straight down, possible causes are a porous block, oil gallery cup plug, bedplate to cylinder block mating surfaces and seal bore. See proper repair procedures for these items.
4. If no leaks are detected, pressurize the crankcase as previously described in 5 under ENGINE OIL LEAK INSPECTION. CAUTION: Do not exceed 20.6 kPa (3 psi).
5. If the leak is not detected, very slowly turn the crankshaft and watch for leakage. If a leak is detected between the crankshaft and seal while slowly turning the crankshaft, it is possible the crankshaft seal surface is damaged. The seal area on the crankshaft could have minor nicks or scratches that can be polished out with emery cloth. CAUTION: Use extreme caution when crankshaft polishing is necessary to remove minor nicks and scratches. The crankshaft seal flange is specially machined to complement the function of the rear oil seal.
6. For bubbles that remain steady with shaft rotation, no further inspection can be done until disassembled.
7. After the oil leak root cause and appropriate corrective action have been identified, replace component(s) as necessary.

CYLINDER-TO-CYLINDER LEAKAGE TEST

To determine if an engine cylinder head gasket is leaking between adjacent cylinders, follow the procedures in CYLINDER COMPRESSION PRESSURE TEST . An engine cylinder head gasket leaking between adjacent cylinders will result in approximately a 50-70% reduction in compression pressure.

CYLINDER-TO-WATER JACKET LEAKAGE TEST

VISUAL TEST METHOD

With the engine cool, remove the coolant pressure cap. Start the engine and allow it to warm up until thermostat opens.

If a large combustion/compression pressure leak exists, bubbles will be visible in the coolant.

CHEMICAL TEST METHOD

Combustion leaks into the cooling system can also be checked by using Bloc-Chek Kit C-3685-A or equivalent. Perform test following the procedures supplied with the tool kit.

Scheme 184

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Scheme 207

1. Perform the fuel system pressure relief procedure. Refer to «STANDARD PROCEDURE»(ref-306144-S17322326742008120900000) .
2. Disconnect and isolate the negative battery cable.
3. Drain the cooling system. Refer to «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
4. Remove the air cleaner element housing. See «REMOVAL»(ref-306143-S23132016952008120900000) .
5. Remove the upper intake manifold including EGR tube, PCV, purge and power brake booster vacuum hoses. See «REMOVAL»(ref-306143-S33795118172008120900000) .
6. Remove fuel rail and lower intake manifold. See «REMOVAL»(ref-306143-S33795118172008120900000) .
7. Disconnect two washer pump hoses, coolant recovery hose and washer pump electrical connector from the coolant recovery/washer fluid reservoir assembly (1).
8. Remove 5 screws and remove the coolant recovery/washer fluid reservoir assembly (1).
9. Disengage the radiator hose retainer (3) from the electric fan shroud.
10. Remove transmission cooling line retainer bolt (2) from the electric fan shroud.
11. Disconnect the electric fan connector (2) from the electric fan shroud.
12. Remove two bolts (1) and lift the electric fan shroud from vehicle.
13. Using Tool 6958 and adapter pins 8346 (1), remove fan/viscous fan drive assembly. Refer to «REMOVAL»(ref-306154-S21887878352008120900000) .
14. Remove accessory drive belt (7). Refer to «REMOVAL»(ref-306154-S30160988302008120900000) .
15. Remove the power steering belt (1). Refer to «REMOVAL»(ref-306154-S30160988302008120900000) .
16. Remove the generator. Refer to «REMOVAL»(ref-306161-S35576092952008120900000) .
17. Remove two nuts (4) and (6) that secure the front of the A/C compressor (1).
18. Back out the two A/C compressor mounting studs (3) and (5) from the accessory drive bracket.
19. Remove four bolts (1) and nut (3) and remove the accessory drive bracket (2).
20. Remove crankshaft damper bolt.
21. Using puller 1023 (1) and insert 9020-R (2), remove crankshaft damper.
22. Remove the fourteen outer timing belt cover bolts and cover (1).
23. Rotate the engine to TDC and align timing belt marks (1,8,9).
24. Raise and support the vehicle.
25. Remove front exhaust pipe to exhaust manifold mounting bolts (3) and (5).
26. Remove bolt (2) and reposition oil cooler hose (1).
27. Remove the timing belt tensioner (12) and reset the tensioner. See «REMOVAL»(ref-306143-S00487284032008120900000) .
28. Lower vehicle.
29. Remove the timing belt (4).
30. Disconnect wire harness connectors from EGR valve, capacitor, and ignition coils (1). Release wire harness track retainer tabs from cylinder head cover.
31. Disconnect electrical connectors from PCM (1), A/C high pressure switch (2), body harness (3), A/C compressor clutch and reposition engine wire harness.
32. Remove the EGR valve (2) with two bolts (6) and gasket.
33. Remove right ignition coils (3). Refer to «REMOVAL»(ref-306179-S22107179072008120900000) .
34. Remove right spark plugs. Refer to «REMOVAL»(ref-306179-S10187668952008120900000) .
35. Remove eight bolts and right cylinder head cover.
36. Remove ten bolts and right rocker arm assembly (2).
37. Remove three bolts (2) and the right rear camshaft thrust plate (1).
38. Counterhold the cam gear and remove the right cam gear retaining bolt.
39. Remove the right cam gear.
40. Remove the three inner timing cover to right cylinder head retaining bolts (1).
41. Remove the cylinder head bolts in REVERSE of tightening sequence.
42. Push the camshaft (5) out of the back of the cylinder head approximately 3.5 inches and remove the cylinder head.
43. Clean and inspect all mating surfaces. If replacing cylinder head assembly, transfer capacitor and exhaust manifold.

Scheme 208

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Scheme 210

1. Perform the fuel system pressure relief procedure. Refer to «STANDARD PROCEDURE»(ref-306144-S17322326742008120900000) .
2. Disconnect and isolate the negative battery cable.
3. Drain the cooling system. Refer to «STANDARD PROCEDURE»(ref-306154-S25259837052008120900000) .
4. Remove the air cleaner element housing. See «REMOVAL»(ref-306143-S23132016952008120900000) .
5. Remove the upper intake manifold including support brackets, EGR tube, PCV, purge and power brake booster vacuum hoses. See «REMOVAL»(ref-306143-S33795118172008120900000) .
6. Remove fuel rail and lower intake manifold. See «REMOVAL»(ref-306143-S33795118172008120900000) .
7. Disconnect two washer pump hoses, coolant recovery hose and washer pump electrical connector from the coolant recovery/washer fluid reservoir assembly (1).
8. Remove 5 screws and remove the coolant recovery/washer fluid reservoir assembly (1).
9. Disengage the radiator hose retainer (3) from the electric fan shroud.
10. Remove transmission cooling line retainer bolt (2) from the electric fan shroud.
11. Disconnect the electric fan connector (2) from the electric fan shroud.
12. Remove two bolts (1) and lift the electric fan shroud from vehicle.
13. Using Tool 6958 and adapter pins 8346 (1), remove fan/viscous fan drive assembly. Refer to «REMOVAL»(ref-306154-S21887878352008120900000) .
14. Remove accessory drive belt (7). Refer to «REMOVAL»(ref-306154-S30160988302008120900000) .
15. Remove the power steering belt (1). Refer to «REMOVAL»(ref-306154-S30160988302008120900000) .
16. Remove the generator. Refer to «REMOVAL»(ref-306161-S35576092952008120900000) .
17. Remove two nuts (4) and (6) that secure the front of the A/C compressor (1).
18. Back out the two A/C compressor mounting studs (3) and (5) from the accessory drive bracket.
19. Remove four bolts (1) and nut (3) and remove the accessory drive bracket (2).
20. Remove crankshaft damper bolt.
21. Using puller 1023 (1) and insert 9020-R (2), remove crankshaft damper.
22. Remove the fourteen outer timing belt cover bolts and cover (1).
23. Rotate the engine to TDC and align timing belt marks (1,8,9).
24. Raise and support the vehicle.
25. Remove front exhaust pipe to exhaust manifold mounting bolts (3) and (5).
26. Remove bolt (2) and reposition oil cooler hose (1).
27. Remove the timing belt tensioner (12) and reset the tensioner. See «REMOVAL»(ref-306143-S00487284032008120900000) .
28. Lower vehicle.
29. Remove the timing belt (4).
30. Disconnect wire harness connectors from knock sensor and ignition coils (1). Release wire harness track retainer tabs from cylinder head cover.
31. Remove left ignition coils (3). Refer to «REMOVAL»(ref-306179-S22107179072008120900000) .
32. Remove left spark plugs. Refer to «REMOVAL»(ref-306179-S10187668952008120900000) .
33. Remove dipstick retaining bolt and remove dipstick tube.
34. Remove eight bolts (2) and left cylinder head cover (1).
35. Remove ten bolts and left rocker arm assembly (2).
36. Remove three bolts (2) and the left camshaft thrust plate (1).
37. Counterhold the left cam gear and remove the cam gear retaining bolt.
38. Remove the cam gear.
39. Remove the four inner timing cover to left cylinder head retaining bolts (1) and (2).
40. Remove the cylinder head bolts in REVERSE of tightening sequence.
41. Push the camshaft (5) out of the back of the cylinder head approximately 3.5 inches and remove the cylinder head.
42. Clean and inspect all mating surfaces. If replacing cylinder head, transfer exhaust manifold.

LASH ADJUSTER (TAPPET) NOISE DIAGNOSIS

Proper noise diagnosis is essential in locating the source of a NVH complaint. Locating a lash adjuster (tappet) type noise can sometimes be difficult. As a result, an initial misdiagnosis may occur.

Refer to the following chart indicating possible lash adjuster (tappet) noise sources and possible sources that could lead to a misdiagnosis.

Refer to LASH ADJUSTER (TAPPET) NOISE CHART for Possible Causes and Correction of a lash adjuster (tappet) type noise.

LASH ADJUSTER (TAPPET) NOISE CHART

Scheme 211

Use this procedure to manually bleed aerated oil from the lash adjuster and remove sponginess.

Scheme 212

1. Run the engine, bringing it to operating temperature in order to freshly pressurize and warm the valvetrain system oil supply.
2. Remove cylinder head cover(s).
3. Ensure the rocker arm is positioned on the base circle (1) of the cam. (Scheme 211) Rotate engine as necessary. 1 - SPECIAL TOOL 8351 2 - OIL AIR RELIEF SERVICE ACCESS HOLE 3 - ROCKER ARM ASSEMBLY 4 - INTERNAL CHECK BALL 5 - VALVE TIP 6 - HYDRAULIC LASH ADJUSTER WITHIN ROCKER ARM
4. For intake rocker arm positions: Adjust Special Tool 8351 (1) Release Probe's gauge pin to extend approximately 20 mm (0.787 in.). Then, carefully insert the release probe gauge pin into the lash adjuster (6) service access hole (2). (Scheme 212) CAUTION: If probe tip (1) breaks off within the lash adjuster (6), replace the affected rocker arm (3). Gently unseat lash adjuster's internal check ball (4). While the internal check ball (4) is held unseated, press the rocker arm (3) into the valve tip (5), allowing the lash adjuster (6) to fully collapse. Hold this fully collapsed position for about one second, or longer. Slowly release the rocker arm (3), thereby allowing the lash adjuster (6) to extend, which in turn refills the high pressure chamber with non-aerated oil. Remove probe to allow check ball (4) to seat. Recheck for sponginess. If the lash adjuster (6) sponginess is not completely or nearly eliminated, then repeat procedure. If the spongy condition cannot be removed, replace effected rocker arm(s) (3).
5. For exhaust rocker arm (3) positions: Adjust Special Tool 8351 (1) Release Probe gauge pin to extend approximately 20 mm (0.787 in.). Then, using two release probes, carefully insert gauge pins into the lash adjuster service access holes. (Scheme 212) CAUTION: If probe tip (1) breaks off within the lash adjuster (6), replace the affected rocker arm (3). Gently unseat BOTH lash adjuster's internal check ball (4) at the same time. While the internal check ball (4) is held unseated, press the rocker arm (6) into the valve tip, allowing the lash adjuster to fully collapse. Hold this fully collapsed position for about one second, or longer. Slowly release the rocker arm (3), thereby allowing the lash adjuster (6) to extend, which in turn refills the high pressure chamber with non-aerated oil. Remove probes (1) to allow check balls (4) to seat. Recheck for sponginess. If the lash adjuster (6) sponginess is not completely or nearly eliminated, then repeat procedure. If the spongy condition cannot be removed, replace effected rocker arm(s) (3).
6. Install cylinder head cover(s).

Scheme 213

1. Remove cylinder head covers. See «REMOVAL»(ref-306143-S09043848162008120900000).
2. Identify the rocker arm assembly and rocker arms before disassembly. (Scheme 213)
3. Remove rocker arm assembly bolts.
4. Remove rocker arm assembly.

Note. To prevent air ingestion into lash adjusters, avoid turning rocker arm assembly upside down.

Scheme 214

1. Remove rocker arm and shafts. See «REMOVAL»(ref-306143-S41312733922008120900000).
2. Remove dowel pin using a 4 mm screw, nut, spacer, and washer installed into the pin. (Scheme 214) Thread the screw into the pin, then loosen the nut on the screw. This will pull the dowel out of the shaft support. Do not reuse dowel pins. Remove the rocker arms and pedestals in order.
3. Check the rocker arm mounting portion of the shafts for wear or damage. Replace if damaged or heavily worn.
4. Check shaft oil holes for clogging with small wire, clean as required.

Scheme 215

The rocker arm shafts are hollow and are used as lubrication oil ducts. The rocker arm and shaft assembly on the right side of the engine has an oil passage hole from the cylinder head located at the third rocker shaft support pedestal. The rocker arm and shaft assembly on the left side of the engine has an oil passage hole from the cylinder head located at the second rocker shaft support pedestal.

Note. To prevent air ingestion into lash adjusters, avoid turning rocker arm assembly upside down.

The intake and exhaust rocker arms are different. They should be identified before disassembling the assembly. (Scheme 215)

Scheme 216

Check rocker arms for wear or damage. (Scheme 216)

1. Roller scuffing or wear
2. Shaft bore scuffing or wear
3. Swivel pad on lash adjuster missing or broken
4. Rocker arm showing signs of fatigue or cracking
5. Roller axle protruding from arm

Replace assembly as necessary if any rocker arms shows signs of wear.

Scheme 217

1. Install the rocker arms, and pedestals (3) onto the shaft.
2. Install dowel pins (2). (Scheme 217) Dowel pins (2) pass through the pedestal (3) into the exhaust rocker shafts. Dowel pins (2) should be pressed in until they bottom-out against the rocker shaft in the pedestal (3).
3. Install rocker arm and shafts. See «INSTALLATION»(ref-306143-S12715012362008120900000).