Engine Disassembly, Cleaning,
and Crack Detection
Use the Proper Disassembly Procedure
•When an engine is operated, it builds up internal
stresses. Even cast iron parts such as cylinder heads
can warp if the proper disassembly procedure is not
followed.
•To disassemble any engine without causing harm, just
remember these two important points:
• Disassemble parts from an engine only after it has
been allowed to sit for several hours.
•All engines should be disassembled when the
engine is at room temperature.
Use the Proper Disassembly Procedure
•Always loosen retaining bolts/nuts in the reverse
order of assembly.
•Most vehicle manufacturers recommend tightening
bolts from the center of the component such as a
cylinder head toward the outside (ends).
Use the Proper Disassembly Procedure
•Therefore, to disassemble the engine, the outside (outer) bolts should be
loosened first, followed by bolts closer to the center.
Taking these steps will help reduce the possibility of warpage
occurring when the parts are removed.
Engine Disassembly
The piston assemblies must exit the deck side of
the block.
Engine Disassembly
The crankshaft should be the last major
component removed from the engine.
All camshaft bearings must be removed.
Engine Disassembly
All core plugs and threaded inserts must be
removed before the engine is cleaned.
Engine Disassembly
All parts/bolts should be bagged and labeled
prior to storage. This is your responsibility!
These connecting
rods were numbered
from the factory.
•If the rods
and mains are
not marked, it
is wise to use
a punch to
make
identifying
marks before
disassembly
of the engine.
•The
orientation of
the rods, caps
and pistons
must also be
noted.
Most engines such as this
Chevrolet V-8 with 4-bolt main
bearing caps have arrows
marked on the bearing caps
which should point to the
front of the engine.
Courtesy of Sealed Power Corporation
If the ridge at the top of a cylinder is
not removed, the top piston ring
could break the second piston ring
land when the piston is pushed out
of the cylinder during disassembly,
or the second piston ring land could
break when the engine is first run
after reassembly with new rings.
Ridge being
removed with one
type of ridge
reamer before the
piston assemblies
are removed from
the engine.
Puller being used
to pull the vibration
damper from the
crankshaft.
Worn timing chain on a highmileage engine.
Notice that the timing chain
could “jump a tooth” at the
bottom of the smaller
crankshaft gear where the
chain is in contact with fewer
teeth.
Notice also that the technician
placed all of the bolts back in
the block after removal of the
part.
This procedure helps protect
against loss or damaged bolts
and nuts.
This defective
cylinder head
gasket was
discovered as soon
as the head was
removed. This
cylinder head will
require machining
or replacement.
A torch is used to heat gallery
plugs.
Paraffin wax is then applied and
allowed to flow around the
threads.
This procedure results in easier
removal of the plugs and other
threaded fasteners that cannot
otherwise be loosened.
Mechanical Cleaning
• Scraping
– Putty knife
• Used on iron or steel parts
– Brass putty knife
• Use WITH CAUTION on aluminum parts
• Brushing
– Use only with iron or steel heads
An air-powered grinder
attached to a bristle pad
being used to clean the
gasket surface of a
cylinder head. The color
of the bristles indicates
the grit number.
The white is the finest
and should be used on
aluminum. Yellow is
coarse and can be used
on aluminum. Green is
designed for cast-iron
parts only.
This type of cleaning
pad should not be used
on the engine block
where the grit could get
into the engine oil and
cause harm when the
engine is started and run
after the repair.
Water-Based Cleaning
• Most chemical cleaning is now performed
using water-based (aqueous-based)
solutions due to environmental concerns.
• Most water-based chemicals are now
silicate based and mixed with water.
– Note: The silicates protect aluminum against
corrosion and turning black!
Spray Washing
• Faster than soaking
• Cycles are generally 30 minutes long
• A water-based chemical is heated to 160 180 degrees and sprayed onto the parts.
– Chemicals must also contain an anti-foaming
agent.
A pressure jet washer
is similar to a large
industrial-sized
dishwasher. The
part(s) is then rinsed
with water to remove
chemicals or debris
that may remain on
the part while it is still
in the tank.
Thermal Cleaning
• Baking is advantageous because …
– It cleans the inside as well as the outside.
– The waste generated is non-hazardous.
• Best suited for cleaning cast iron.
– Parts are baked at temperatures between 666
and 800 degrees.
• Aluminum should not be baked over 600
degrees. (cylinder heads over 400 degrees).
Thermal Cleaning (cont.)
• A disadvantage of baking is that it leaves a
dull and burnt appearance.
• A shot blaster is usually used to enhance
appearance.
Airless blaster
Pyrolytic oven
A pyrolytic (high temperature)
oven cleans by baking the engine
parts.
After the parts have been
cleaned, they are then placed into
an airless blaster. This unit uses
a paddle to scoop stainless steel
shot from the reservoir and
forces it against the engine part.
The parts must be free of grease
and oil to function correctly.
Blasting
• Small solid particles are blasted using
compressed air.
–
–
–
–
–
Sand
Glass
Steel
Iron
Aluminum
Stainless steel shot used
in an airless blaster.
Engine block after being
cleaned in a pyrolytic oven
and airless blaster.
Airless Blaster
• The steel shot from an airless blaster will
lodge into any and all holes in an engine
block.
– For this reason the block must be thoroughly
blown out with compressed air.
– All threaded holes must be tapped or thread
chased!
Small engine parts
can be blasted clean
in a sealed cabinet.
Chemical Cleaning
• Deposits or debris that can be dissolved
with a chemical are said to be soluble.
• Carbon deposits are removed with
chemicals that are said to be caustic.
– Caustic materials are highly corrosive, therefore
they should be neutralized with water and then
air-blown after cleaning.
Chemical Cleaning
• Chemicals are classified by a pH value
between 1 and 14
– Pure water is neutral and given a value of pH7.
• Caustic chemicals are rated between 8 and 14 on the
pH scale. The higher the number the higher its
causticity.
• Acid materials are rated between 1 and 6. The lower
the number, the greater the acid property.
Chemical Cleaning
Caustics and acids
neutralize each other.
Parts Cleaning
•
•
•
•
Cold tank cleaning
Hot tank cleaning
Vapor cleaning
Vibratory cleaning
Parts Inspection
• After parts have been thoroughly cleaned
they should be checked for defects.
– Visual inspection - dugh
Magnaflux
• Magnetic crack inspection
• The part is connected to a large
electromagnet.
• Magnetic lines of force are more
concentrated along the edges of a crack.
• A fine iron powder is applied to the part,
being more concentrated on the edges of a
crack.
– A brand name
– Used on iron or steel parts
If the lines of force are
interrupted by a break
(crack) in the casting,
two magnetic fields are
created and the powder
will lodge in the crack.
A strong electromagnet
can be used to check a
cast-iron cylinder head
for cracks.
The cylinder head
should be thoroughly
cleaned and placed on
a work surface that
gives good visibility.
Turn the electromagnet
on using the switch at
the top and spray a fine
iron powder between the
poles of the magnet.
The magnetic lines of
force are more
concentrated on the
edges of a crack, and the
iron powder will be
attracted to the strong
magnetic concentration
around the crack.
Pay particular attention
to the area around and
between the valve seats.
This cylinder head has
cracks running from
two valve seats. The
head will either have to
be replaced or repaired.
This crack in a
vintage Ford 289,
V-8 block was
likely caused by
the technician
using excessive
force trying to
remove the plug
from the block.
Crack
The technician
should have used
heat and wax, not
only to make the
job easier, but also
to prevent
damaging the
block.
Crack in cylinder wall
Soapy water spray bottle
To make sure that the mark
observed in the cylinder wall
was a crack, compressed air
was forced into the water jacket
while soapy water was sprayed
on the cylinder wall.
Bubbles confirmed that the
mark was indeed a crack.
Pressure Testing
• Coolant passages are sealed and compressed
air is forced into them.
• The component is then lowered into a water
tank – air bubbles will appear if a crack is
detected.
A cylinder head is under
water and being
pressure tested using
compressed air.
Note that the air bubbles
indicate a crack.
Dye Penetrate Testing
• Used on non-magnetic
materials.
– A red penetrating
chemical is sprayed
onto the component
and then cleaned.
– A white or yellow
powder is then applied.
• A UV lamp is used to
view the part.
• staining will occur if a
crack is present.
(a) Before welding, the crack is ground
out using a carbide grinder.
(b) Here the technician is practicing
using the special cast-iron welding
torch before welding the cracked
cylinder head.
(c) The finished welded crack before
final machining.
(d) The finished cylinder head after the
crack has been repaired using
welding.