Tightening and Check of Connecting Rod Screws

08028-0D/H5250/94.08.12

Safety precautions:

Stopped engine

Shut-off starting air

Shut-off cooling water

Shut-off fuel oil

Shut-off cooling oil

Stopped lub. oil circul.

Description:

Tightening procedure for connecting rod screws. Check of connecting rod screws, tightening condition.

Starting position:

Piston, connecting rod, bearing shells

Related procedure:

Tool combinations for tightening of connecting rod screws, see working card 520-01.20.

Hand tools:

Open-end spanner, 24 mm.

Replacement and wearing parts:

L23/30H

Tool combinations for tightening of connecting rod screws, see working card 520-01.20.

Tightening of Connecting Rod Screws

1st Step:

Tightening the screws in tightening order, illustrated in fig 1, using an initial torque of 250 Nm.

Fig 1.

2nd Step:

Once more, tightening the screws in prescribed tightening order, still using a torque of 250 Nm.

3rd Step:

Mark the four screws and the bearing cap felt-tippen, illustrated in fig 2.

Mark on screw collar

Mark on bearing cap

60°

Fig 2.

4th Step:

Check the screw tightening in prescribed order using a torque of 325 Nm.

Proper tightening condition is present, if the screws are not turned further during this test.

5th Step:

Check that the bearing can easily be moved on the journal.

Check of Connecting Rod Screws, Tightening

Condition:

Check of the tightening condition of connecting rod screws has to be executed within a short running period after remounting/mounting of the connecting rod.

This check can be fulfilled after only a few running hours at max. rpm at full load, but has to be fulfilled not later than 200 running hours after starting-up.

The tightening condition is checked with a torque af 325 Nm, executed in prescribed screw tightening order, see fig 1.

08028-0D/H5250/94.08.12

Tightening order by turning through a 60° ± 2° angle, i.e. until the marks on the screw collar and the connecting rod coincide radially.

Proper tightening condition is present, if the screws are not turned further during the test.

In order to ensure observation of any movement, the screws and the connecting rod should be applied with coinciding filt-pen marks prior to the test, see fig 3.

Mark on screw collar

Coinciding mark on bearing cap

Fig 3.

Any turning of the screws during the 325 Nm test indicates insufficient tightening condition, and in this case the big-end assembly has to be dismantled and investigated for evaluation and correction of failure.

As part of recommended overhaul and routine work, the tightening condition of connecting rod screws should also be checked, at certain running hours intervals, see page 500.24.

Nm

08028-0D/H5250/94.08.12

Safety precautions:

Stopped engine

Shut-off starting air

Shut-off cooling water

Shut-off fuel oil

Shut-off cooling oil

Stopped lub. oil circul.

Description:

In-situ inspection and/or replacement of connecting rod big-end bearing, dismounting and mounting.

Top cover for cylinder head removed.

Tool combination for tightening of connecting rod screw, see working card 520-01.20.

Hand tools:

Open-end spanner 24 mm.

Replacement and wearing parts:

Dismounting of Bearing Cap

3)Remove the fuel injector.

4)Insert the long-eye bolt and screw it into the thread hole in the piston, see fig 2.

5)Tighten it slightly by means of a tackle, see fig

2.

Removal of Bearing Shells

6) Dismount the bearing cap and bearing shell. For use of guide pin, see working card 506-01.00.

7) Lift the piston/connecting rod from the bearing journal.

Note: the piston/connecting rod should be lifted further then, just to allow dismounting of the upper bearing shell, see fig 2.

Inspection of Bearing Shells

8) Inspect the bearing shells, see working card

506-01.16.

08028-0D/H5250/94.08.12

Fig 3.

Cleaning of Components before Mounting.

9) Clean all components, see working card 50601.20.

Mounting of Upper Bearing Shells

10) The bearing shell is placed in the bore, the contact surfaces of the shells to be in parallel to the contact surface of the connecting rod and the bearing cap respectively.

08028-0D/H5250/94.08.12

11)Ascertain that the crank throw concerned is in a position of approx 50 degrees before TDC.

12)Coat the journal with clean lubricating oil and lower the piston and connecting rod assembly slowly into correct landing on the journal.

While lowering the connecting rod, it must be guided by hand to ensure a correct approach and landing on the journal, see fig 4.

13) Lubricate the ends of the bearing shells (as in fig 2) with copaslip, molycote or simular.

Mounting of Bearing Cap

14)Mount the bearing cap with inserted lower bigend bearing shell, using the guide pin.

15)Lubricate threads and contact face of the connecting rod screws with copaslip or similar.

16)Mount the screws and tighten them slightly using an open-end spanner.

17)Slacken the tackle and dismount the eye screw from the piston crown.

Tightening of Connecting Rod Screws

18) Tighten the screws according to "Tightening Procedure for Connecting Rod Screw", see working card 506-01.25.