Removal and repair of the Cummins ISF3.8 flywheel

Removal, dismantling, inspection and installation of the Cummins ISF3.8 engine flywheel

The engine flywheel is removed during a major engine overhaul or to replace the ring gear. Removing and installing the flywheel requires care: correct bolt tightening and the condition of the contact surfaces affect clutch operation and engine starting.

We prepare the vehicle for the task. We disconnect the negative battery terminal.

We remove the transmission assemblies.

We remove the flywheel, for this:

Models with a “wet” clutch: we drain the oil from the clutch housing by unscrewing the plug from its lower part.
Using retainer No. 3824591, we lock the flywheel against rotation.
We unscrew two bolts located opposite each other.
We install two guide pins M12×1.25×90 mm.

We determine the type and size of the bolts and install two T-handles in the flywheel holes (1) and (2).

Fig. 3. Installing the T-handles in the flywheel holes.

Note: if the design includes a clutch, the pressure plate mounting bolt holes may be metric or imperial threaded. Do not make a mistake when selecting the bolts.

We unscrew the remaining six flywheel mounting bolts.
We remove the flywheel from the guide pins.

Dismantling, inspection and repair of the flywheel

Inspecting the pilot bearing — Fig. 4. Inspecting the gearbox input shaft pilot bearing.

We inspect the condition of the gearbox input shaft pilot bearing pressed into the flywheel bore. If there is excessive play or seizing of the rolling elements, the bearing must be replaced.

Bearing removal — Fig. 5. Removing the pilot bearing with a drift.

We remove the pilot bearing using a drift and a hammer.
We clean the bearing seat with fine abrasive paper.
We check the flywheel surface for scores and burrs.

Fig. 6. Inspecting the flywheel surface.

Minor defects can be removed with abrasive paper.

Removing defects — Fig. 7. Removing minor defects with abrasive paper.

We check the flywheel ring gear for wear and damaged teeth. If necessary, we replace the flywheel ring gear, for this:

Fig. 8. Knocking off the ring gear with a copper bar.

using a copper bar, we knock off the ring gear;

Fig. 9. Heating the ring gear in an oven.

we heat the new ring gear for 20 minutes in an oven preheated to 127°C;

Fig. 10. Installing the ring gear on the flywheel.

we install the ring gear on the flywheel with the chamfered side of the teeth towards the crankshaft.

Flywheel assembly

Installing a new bearing — Fig. 11. Installing a new pilot bearing.

We install the new pilot bearing using a hammer and a drift.

Flywheel installation

Installing the guide pins in the flange — Fig. 12. Installing the guide pins in the crankshaft flange.

We install two guide pins M12×1.25×90 mm in the crankshaft flange holes opposite each other.
We determine the type and size of the bolts and install two T-handles in the flywheel holes (1) and (2).

Note: if the design includes a clutch, the pressure plate mounting bolt holes may be metric or imperial threaded. Do not make a mistake when selecting the bolts.

Fig. 13. Preparation for flywheel installation.

We check the rear end of the crankshaft and the flange under the flywheel for dirt and protruding scores and burrs.
We install the flywheel on the guide pins.
We lubricate the bolt threads and washers with clean engine oil.

Installing the mounting bolts — Fig. 14. Installing the flywheel mounting bolts.

We install six bolts.
We remove the T-handles and guide pins (1) and (2).
We install the remaining bolts in the holes from which the guide pins were removed.
We lock the crankshaft against rotation using tool No. 3824591 for holding the flywheel stationary.

Fig. 15. Locking the flywheel with tool No. 3824591.

We tighten the bolts in the sequence shown in the figure. Tightening torque: first stage – 30 N·m; second stage – turn a further 90°.

Checking flywheel runout

Installing the dial indicator for runout checking — Fig. 16. Installing a dial indicator to check flywheel runout.

We determine the flywheel (4) face runout using a dial indicator (1) and a dial indicator holder (2):

we install the holder on the flywheel housing;
we secure the gauge on the holder;
we place the indicator plunger on the flywheel face at the radius specified in the table, as close as possible to its outer diameter, to measure the flywheel face (1) runout;
we push the flywheel forward to take up the crankshaft end play. We set the indicator to zero;
we turn the crankshaft one revolution. We measure and record the flywheel runout at four equally spaced points around its circumference.

Always push the flywheel forward for each measurement to take up the crankshaft end play.

Measuring runout — Fig. 17. Measuring flywheel runout.

we determine the total runout. Total runout is defined as the difference between the maximum and minimum indicator readings at the four measurement points.