Cleaning & inspection

The following Impact documents are used:

Cylinder head, pressure test (first) 21171-4
Camshaft wear, check 21516-2
Crankshaft, inspection and renovation 216 / repair / D12A / crankshaft
Connecting rod bushing, changing 216 / repair / con.rod
Flywheel ring gear, replace 21687-5
Oil cooler, pressure test 22325-5
Coolant pump, replace 26202-2
Thermostats, test 26273-4

INSPECTION OF ENGINE PARTS

Engine parts should be inspected and evaluated using the measurements and wear
tolerances found in the engine specifications. The inspection can be carried out in a
different order, but for this course concept we shall follow the grouping in the
specification.
Note! Always ensure that you use the most up to date engine specification, as factors
such as wear tolerances can change.

CYLINDER BLOCK
Do not use a drill or screw tap when cleaning threads in the cylinder block.
Check the threads in the upper block surface and clean if necessary. Check cylinder
liner contact surfaces. If there is any corrosion or other damage, the cylinder block
must be replaced. The liner seat cannot be machined and no shims are available as
spare parts.
The upper surface of the block must not be machined for the same reason as for the
cylinder head surface.
Look at the end plugs for the piston cooling and lubrication passages in the block.
These plugs must be removed and new ones fitted if the passages are to be cleaned.

If there is any damage to the block’s main bearing seats or in the main bearing caps,
the block must be rectified in a machine shop. Main bearing caps are available as a
spare part, but they do not have machined bearing seats.

CYLINDER LINER
The cylinder liners can be reused if they are free from defects. In such cases the
corresponding piston must also be free from defects because pistons and liners are
not available as separate items.
Note! Pistons and liners are tolerance-classified and supplied as one kit. Because of
this, they must not be confused when fitting.

Inspect the surface of the liner under the liner collar. There must not be any
corrosion.

Inspect the outside of the liner. There must be no signs of damage due to cavitations.

Inspect the inside of the liner. Replace the liners if there are any scratches or
polished spots. There is no maximum value specified in respect of wear in the current
service literature. As a general guide, a prominent ridge left by the top piston ring will
mean it is time to change the liner.

PISTONS
Inspect the piston skirts. There should not be any scratches, cut marks or cracks.

There should not be any cracks in the gudgeon pin circlip groove. Check piston ring
grooves and piston rings using the measurements given in the specifications.

Look at the piston’s assembly marking with the arrow facing forward. The piston ring
markings must be face up. The piston ring markings can consist of numerals/letters
or a stamp.

Piston rings and liner seals are available as separate spare parts and can be
replaced as long as the piston and liner are free from defects.

ROCKER ARMS
Check the play of the rocker arm bushings on the rocker arm shaft and the play in the
rocker arm cylinder bushing. If these measurements exceed the specified values, the
rocker arm must be replaced.

ENGINE TIMING GEAR

Inspect the timing gear teeth surfaces for wear.
The nozzle for lubricating the gears must be blown clean.

CAMSHAFT
Inspect the camshaft and compare with the specifications. If the cam profile is worn,
refer to Op. 21516-2 for measuring the wear.
Turn the camshaft. Check the camshaft with regard to wear on the camshaft lobes
and damage to the surfaces.
Unevenness can develop on cam lobe surfaces during normal operation. This does
not mean the camshaft must be replaced.
Figure 1 shows examples of scoring that will not affect the running of the engine.
Camshafts with this type of scoring need not be replaced.
Figure 2 shows examples of camshafts with such damage that they must be
replaced.
The camshaft bearing journals cannot be reground and bearing shells are only
available in one size.

CRANKSHAFT
Inspect the crankshaft as described in the information in 216/repair/D12A/crankshaft.
The crankshaft bearing journals can be reground and bearing shells are available in
over dimensions. For thorough cleaning of the oil channels, the end plugs have to be
removed. When refitting the plugs use some locking fluid.

Firstly, the alignment of the crankshaft needs to be inspected. If the alignment

exceeds the permitted tolerances, the crankshaft must be scrapped. It is forbidden to
straighten it.
The crankshaft's alignment can be measured whilst still in situ in the block, but it
must be supported by bearing shells number 1 and 7. Use the magnetic stand, the
indicator gauge and special tool no. 9998583 or 9996390 as an extension.
Alternatively, the alignment can be checked with the crankshaft positioned on two V-
blocks.

OSCILLATION DAMPER
The only way to check the oscillation damper is to put it on a dry surface with the rear
facing down. Wait for half an hour and check for any leakage from the welding.

The function of the oscillation damper cannot be checked without special equipment.
It is only possible to perform an external visual inspection.

If there are any indentations in the sides of the damper (from collisions or abuse), it
must be replaced.

Defective dampers can cause crankshaft failure.

CONNECTING ROD
The specifications are used to check if the connecting rods are warped.
This type of check is normally only performed if the engine has had seized pistons
and there is a suspicion of warped connecting rods.

Special equipment that is normally only available in machine shops is required for the
check; refer to Op. 216/repair/D12A/Connecting rod.

The connecting rod has a front marking arrow that must point forwards in the engine.

Changing the gudgeon pin bushing is also a job that should be performed in a
machine shop, because the bushing must be ground to the correct inner diameter
after being pressed in.
Note! On the later type of connecting rod with split big ends, it is critical that the split
surfaces are kept clean. Blow clean the surfaces with compressed air before
assembly. Do not use a wire brush or rags that can shred.

FLYWHEEL
Check the teeth on the starter motor ring gear.

When replacing the ring gear, refer to Op. 21687-5. Check that the flywheel number
markings (4 and 6) on the front are easy to see. If necessary, clean and make the
markings more legible.

OIL FILTER HOUSING

Remove all the valves. Check the valves and springs for wear.
Check also the flatness of the sealing surface with a steel rule. Small deviations can
be rectified by grinding on a face plate.

OIL PUMP
The oil pump is only available as a complete unit.
OIL COOLER
The oil cooler can be checked by pressure testing, Op. 22325-5.

INJECTORS
Delivery pipes must not be reused. The injectors cannot be repaired.

FUEL FEED PUMP

The fuel pump is only available as a complete unit.

TURBO
The maximum radial and axial play for the turbocharger is not given in the
specifications.

Check that the turbine or compressor wheel does not scrape against the housing
when the wheel is lifted on the shaft at the same time as it is turned. If the wheels
scrape against the housing, the turbocharger must be replaced.

COOLANT PUMP
Op. 26202-2 describes how the pump section is removed from the rear housing.
Make sure the bearing housing evacuation hole is not blocked.

THERMOSTAT
The coolant thermostat can be checked as per Op. 26273-4. Also mention that the
sealing ring in the cylinder head should be replaced when changing the thermostat.

BOLTS
You can find information on assessing and identifying different classes of bolts under
the heading ”Tightening torques” in the engine specifications.

For example, cylinder head bolts that have been washed and dried should be dipped
in anti-corrosive oil (part no. 1161346-0). Point out the importance of letting them drip
dry before fitting. Otherwise, the oil may leak between the cylinder head and the
block when the engine is started and be mistaken for an oil leak.

CYLINDER HEAD
When overhauling the cylinder head, you only need to perform the task on one
cylinder (in order to save time and spare parts).

Start by checking the flatness of the cylinder head. A perfectly straight ruler (min.
1200 mm long) will be required for this. Measure diagonally and compare with the
specifications.
Note! The cylinder head must not be refaced or machined, as it will affect emissions.

Before removing the valves, show (using Op. 21416-2) how the valve stem seals can
be replaced using tool no. 9998506.
Note! When carrying out this work with the cylinder head on the engine, ensure that
the corresponding piston is at TDC.
In order to get an idea of the condition of the valves and valve seats, the distance
between the valve disc and cylinder head face should be measured before removing
the valves. If the measurement exceeds specifications, you will be able to tell
beforehand that something is worn.

Remove the valves from one cylinder. Follow Op. 21405-5 up to item 4. Remove the
valve stem seals.
If a spring tester is available, the measured values can be compared with the
specifications.

Op. 21417-5 can be used for checking valve guide wear.

Op. 21105-5 describes how to replace the valve seats. This type of work is not
normally performed at a truck workshop. It is instead left to a mechanical workshop
as the entire cylinder head must be heated to about 100 degrees Celsius and the
valve seats have to be cooled to minus 60-70 degrees Celsius. (Exchange cylinder
heads always have new valve seats fitted).

Valve grinding is not allowed because the surfaces are coated. Several methods can
be used to check tightness. Using a colour marker or chalk are the most common.
Using soapy water and compressed air, or thinners/alcohol in the inlet and exhaust
passages are also common methods.

There are a number of plugs in the cylinder head that may need replacing. The fuel
passage end plugs must be removed, for example, to clean the passages.

The coolant plugs for the coolant jacket can be replaced by following Op. 21131-5.
Replace one plug if a spare part plug is available.

Follow Op. 23721-3 or 23703-3 for replacing copper sleeves.

Note! It is essential that you follow the order of tightening given in the specifications.
Point out the importance of using the correct tool to protect the fuel passages.

Before refitting valves and springs, the cylinder head can be pressure tested
according to Op. 21171-4. If a sufficiently large water tank is not available, show how
the sealing tools and test equipment are assembled and used. Skip items 15 and 16
as these will be performed later when assembling the engine.

Follow Op. 21405-5, items 5 to 9, fitting valves.