MBE 900 – Section 1.20 Camshaft

Section 1.20
Camshaft

The camshaft is made of induction-hardened steel and has seven bearing journals (five on the 4-cylinder engine). Each cylinder has cams for intake and exhaust valves and a unit pump.‪

Section 1.20.1
Camshaft Removal

Remove the camshaft as follows:‪

Note: Before removing the camshaft, clean the engine to prevent road dirt, grease, or other foreign matter from contaminating the exposed gears and other engine parts.

1. Drain the engine oil and coolant.
2. Remove the engine.
3. Remove the rocker arm assembly and pushrods. Refer to "1.19.1 Rocker Arm Assembly Removal" .
4. Remove the fuel pump. Refer to "2.15.1 Fuel Pump Removal" .
5. Remove the unit pumps. Refer to "2.1.1 Injector Unit Pump Removal" .
6. Remove the oil pan. Refer to "3.7.1 Oil Pan Removal" .
7. Remove the camshaft TDC sensor at the crankcase. See Figure "Camshaft Assembly" .
   

   1. Camshaft‪	5. Valve Tappet‪
   2. O-ring‪	6. Crankshaft Gear‪
   3. Camshaft TDC Sensor‪	7. Flywheel Housing‪
   4. Pushrod‪	8. Camshaft Gear‪

   Figure 1. Camshaft Assembly

   BODILY INJURY ‪
   To avoid injury from a falling component, ensure a proper lifting device is used. Never stand beneath a suspended load.‪

8. Remove the flywheel housing. Refer to "1.14.1 Flywheel Housing Removal" .

   NOTICE:
   Do not damage the camshaft bearings in the crankcase. If the camshaft bearings are damaged, the crankcase will have to be replaced.‪

9. Attach the camshaft removal/installation tool J-46403 to the front of the camshaft.

   Note: The following step may require two persons. The engine must be inverted (turned upside down) at this point in order to remove the camshaft.

10. Carefully remove the camshaft from the crankcase.
11. Pull the valve tappets out of the crankcase. Mark the valve tappets, in order, as removed.
12. Inspect the valve tappets. Refer to "1.20.1.1 Camshaft Inspection"

Section 1.20.1.1
Camshaft Inspection

Inspect the camshaft as follows:‪

1. Inspect the valve tappets. If damage or wear is present, replace the roller tappets.
   1. Inspect the valve tappet outer diameter, the specifications are listed in Table "Valve Tappet Specifications" .
   2. Inspect the valve tappet bore in the crankcase, the specifications are listed in Table "Valve Tappet Specifications" .

      Description‪		4- and 6-Cylinder:‪ mm (in.)‪
      Valve Tappet Outer Diameter‪		‪
      ‪	Standard‪	17.944–17.965‪ (0.7065–0.7073 )‪
      ‪	Oversize 0.25‪	18.194–18.215‪ (0.7163– 0.7171 )‪
      Valve Tappet Bore in Crankcase Diameter‪		‪
      ‪	Standard‪	18.000–18.018‪ (0.7087–0.7094 )‪
      ‪	Oversize 0.25‪	18.250–18.268‪ (0.7185–0.7192 )‪

      Table 4. Valve Tappet Specifications

   Note: Be aware that in order to get a correct hardness reading, it is critical to place a hard base below the cam or bearing journal. Camshaft specifications are listed in Table "Camshaft Specifications" .

   Description‪		6-Cylinder‪ mm (in.)‪	4-Cylinder‪ mm (in.)‪
   Camshaft Radial Runout When Mounted on Outer Bearing Journals‪		‪	‪
   ‪	Timing Gear Seat Maximum‪	0.020‪ (0.0008 )‪	0.020‪ (0.0008 )‪
   ‪	Cam Base Circle Maximum‪	0.025‪ (0.0010 )‪	0.025‪ (0.0010 )‪
   ‪	All Bearing Points Maximum‪	0.030‪ (0.0012)‪	0.030‪ (0.0012)‪
   Cam Rise—Valve Lobes Over Base Circle Diameter‪		‪	‪
   ‪	Inlet Minimum‪	7.3‪ (0.3)‪	7.3‪ (0.3)‪
   ‪	Exhaust Minimum‪	8.2‪ (0.32)‪	8.2‪ (0.32)‪
   Cam Rise—Unit Pump Over Base Circle Diameter‪		‪	‪
   ‪	Minimum‪	13.8‪ (0.54)‪	13.8‪ (0.54)‪
   Hardness of Cams and Bearing Journals HRc‪		54–60 HRc‪

   Table 5. Camshaft Specifications
2. Using a hardness tester, inspect the hardness of the cams and bearing journals at the camshaft. A hard base should be placed below the cam or bearing journal to be inspected. See Figure "Inspecting Cam Hardness" .
   

   1. Camshaft‪

   2. Hardness Tester‪

   Figure 2. Inspecting Cam Hardness

   Note: For all of the following steps, see Figure "Measuring the Cam Rise" .

3. Mount the camshaft at the outer bearing journals, indicated as B in the next illustration. See Figure "Measuring the Cam Rise" .
   

   1. Camshaft Gear‪	3. Camshaft‪
   2. Dial Gauge‪

   Figure 3. Measuring the Cam Rise

   Note: For all of the following steps, use a dial gauge.

4. Measure the radial runout of the cam base circle or bearing points, shown as B. See Figure "Measuring the Cam Rise" .
5. Measure the cam rise of the inlet valve cams, shown as I. See Figure "Measuring the Cam Rise" .
6. Measure the cam rise of the exhaust valve cams, shown as E. See Figure "Measuring the Cam Rise" .
7. Measure the cam rise of the unit pump valve cams, shown as U. See Figure "Measuring the Cam Rise" .
8. If in any of the preceding steps the camshaft does not meet specifications listed in Table "Camshaft Specifications" , replace it.

Section 1.20.2
Camshaft Installation

Install the camshaft as follows:‪

1. Install the valve tappets in the cylinder block, in locations, as removed. Put a light amount of lube oil on the tappets prior to installation.

   NOTICE:
   Do not damage the camshaft bearings in the crankcase. If the camshaft bearings are damaged, the crankcase will have to be replaced.‪

2. Attach the camshaft removal/installation tool J-46403 to the camshaft.
3. Carefully insert the camshaft into the cylinder block.
   

   1. Camshaft Gear‪

   2. Crankshaft Gear‪

   Figure 4. Camshaft Alignment

4. Rotate the camshaft until the marking "1-1" on the camshaft gear is aligned with the marking "1" on the crankshaft gear. See Figure "Camshaft Alignment" .
5. Install the Flywheel housing. Refer to "1.14.2 Flywheel Housing Installation" .
6. Install the camshaft TDC sensor at the cylinder block.
   1. Replace the O-ring.
   2. Carefully push in the TDC sensor until it makes contact with the camshaft gear.
7. Install the oil pan. Refer to "3.7.2 Oil Pan Installation" .
8. Install the unit pumps. Refer to "2.1.2 Injector Unit Pump Installation" .
9. Install the fuel pump. Refer to "2.15.2 Fuel Pump Installation" .
10. Apply clean engine oil on the pushrods. Then, install the pushrods, and the rocker arm assembly. Refer to "1.19.4 Rocker Arm Assembly Installation" .
11. Install the engine.
12. Fill, pressurize, and attach the engine pre-oiler can.
13. Fill the engine with oil.