Engine Disassembly & Reassembly and Cleaning
Engine Disassembly & Reassembly and Cleaning
Removing an Engine
Preliminary Checks and Preparations:
Consult the service manual for the specific vehicle.
Gather necessary hand tools, special tools, an engine hoist or crane, and a jack.
Be aware that engine removal procedures differ; Front-Wheel Drive (FWD) vehicles often require removal from the bottom, while Rear-Wheel Drive (RWD) vehicles typically allow removal from the hood opening.
Keep the engine exit point in mind while disconnecting components.
General Procedures:
Safety First: Block the wheels to prevent movement.
Protect the vehicle with fender covers.
Relieve fuel system pressure as per manufacturer's instructions.
Use a memory saver before disconnecting the battery to preserve computer settings.
Disconnect the negative battery cable(s), insulate the connectors, and move them away from the battery.
If necessary, remove the positive cables and the battery itself.
Hood Removal:
If possible, prop the hood straight up, otherwise, remove it entirely.
Mark hinge locations before unbolting the hood.
Get assistance to safely remove the hood and store it on a protected surface.
Fluid Drainage:
Drain engine oil and remove the oil filter.
Drain coolant from the radiator and engine block with the engine cool and radiator cap removed to increase flow.
If the transmission is being removed with the engine, drain its fluid as well.
Underbody Disconnections:
Disconnect shift linkage, transmission cooling lines, all electrical connections, vacuum hoses, and clutch linkages from the transmission.
For hydraulically operated clutches, unbolt the slave cylinder and set it aside, or disconnect and plug the line.
Air-Fuel System:
Remove air intake ducts and the air cleaner assembly.
Disconnect and plug the fuel line at the fuel rail.
If present, disconnect the return fuel line from the fuel pressure regulator.
Ensure all fuel lines are sealed off with pinch pliers or appropriate plugs/caps.
Vacuum Lines:
Disconnect all vacuum lines at the engine, labeling them beforehand.
Utilize the vacuum wiring diagram decal under the hood for easier reconnection.
Disconnect the throttle linkage at the throttle body and the electrical connector to the throttle position (TP) sensor.
Accessories:
Remove all drive belts, noting their routing for reinstallation.
Unbolt and move the power steering pump and air conditioning (A/C) compressor out of the way without disconnecting lines if possible.
If A/C lines must be disconnected, have the refrigerant recovered by a certified technician.
Plug all disconnected A/C lines and connections to prevent contamination.
Remove or reposition the A/C compressor bracket, power steering pump, air pump, and any other engine-mounted components.
Disconnect and plug all transmission and oil cooler lines.
Electrical Connections:
Unplug all electrical wires between the engine and the vehicle, using masking tape to label each connection.
Remove the crankshaft position sensor if present above the flywheel or flexplate.
Disconnect the engine ground strap, preferably at the engine.
Cooling System:
Disconnect the heater inlet and outlet hoses and the upper and lower radiator hoses.
Remove the fan shroud and cooling fan; if electric, disconnect the wiring first.
Remove the radiator mounting brackets and the radiator itself, often as a unit with the electric cooling fan assembly.
Exhaust System:
Disconnect the exhaust system, ideally at the exhaust manifold.
Disconnect wires connected to exhaust sensors before moving the system.
Remove any heat shields obstructing engine removal.
Final Checks:
Thoroughly inspect under the hood for anything that might interfere with the engine removal process.
Front-Wheel Drive (FWD) Vehicles
General Approach:
Engine removal is often done from the bottom of the vehicle.
Special tools may be needed to secure the transaxle and/or engine during disconnection.
Always consult the service manual before removing the transaxle.
Use an engine cradle and dolly for bottom removal or an engine hoist for hood removal.
The engine and transaxle are typically removed as a unit.
Drive Axles:
Loosen axle shaft hub nuts while the vehicle is on the ground with brakes applied.
Raise the vehicle and remove the front wheel and tire assemblies.
Tap the CV joint shaft with a soft-faced hammer to loosen it.
Disconnect any necessary suspension and steering parts according to the service manual.
Indexed Parts and Ball Joints:
Index parts to maintain wheel alignment during reassembly.
Separate the lower ball joint from the steering knuckle, either bolted or held with a pinch bolt.
Once loose, pull down the control arm and push the knuckle outward to slide the CV joint shaft out of the hub.
Inboard Joint Removal:
Pry or slide out the inboard joint; some transaxles have retaining clips that need removal first.
For flange-type mountings, unbolt the shafts.
In some cases, leave flange-mounted drive shafts attached to the wheel and hub assembly and unbolt them at the transmission flange.
Support the free ends of the shafts and keep them out of the way.
Remove the drive axles from the transaxle, ensuring brake lines and hoses aren't stressed; suspend them with wire if needed.
Transaxle and Starter Connections:
Disconnect all electrical connectors and the speedometer cable at the transaxle.
Disconnect the shift linkage or cables and the clutch cable.
Remove the starter, either disconnecting it completely or supporting it securely to prevent wire damage or accidental dropping.
Engine Removal Through the Hood:
Attach the engine sling or lifting chains to the engine, using lifting hooks or specified points in the service manual.
Connect the sling to the crane and support the engine weight.
Remove the cross member and engine mounting bolts from underneath the vehicle.
Support the transmission with a transmission jack and remove the transaxle mounts.
Remove all remaining mounts and raise the engine slightly before lifting it out of the engine compartment.
Carefully guide the engine, avoiding damage to surrounding components.
Engine Removal From Under the Vehicle:
Position the engine cradle and dolly, adjusting pegs to fit the engine's recesses.
Secure the engine and remove all engine and transmission mount bolts.
Remove any required frame members.
Disconnect the steering gear from the frame if necessary.
Final Checks and Lifting:
Double-check all wire and hose disconnections.
Support the transmission with a transmission jack and remove the transaxle mounts.
Raise the vehicle, leaving the engine on the cradle.
Monitor for any interference during lifting, ensuring no wires or hoses remain connected.
Rear-Wheel Drive (RWD) Vehicles
General Approach:
Engine removal is typically done through the hood opening using an engine hoist.
Determine the proper engine lift points from the service manual.
Attach a pulling sling or chain to the engine; use eye plates if available or bolt the sling securely to the engine.
Use bolts of sufficient size that thread into the block a minimum of 1\frac{1}{2} times the bolt diameter.
If removing the transmission with the engine, position the hoist hook to slightly tilt the engine towards the transmission.
Lift the engine slightly, checking for any remaining connections.
Transmission Separation:
If separating the engine and transmission, remove all clutch (bell) housing bolts.
For automatic transmissions, remove torque converter mounting bolts.
If removing the transmission with the engine, drain the transmission fluid.
Index the alignment of the rear U-joint and pinion flange with chalk before removing the driveshaft.
Transmission Disconnections:
Disconnect all electrical connections and the speedometer cable at the transmission, protecting them from damage.
Disconnect and remove the transmission and clutch linkage.
Disconnect only the necessary parts of the exhaust system.
Support the transmission with a transmission jack and unbolt the motor mounts.
Engine and Transmission Removal:
If removing the engine with its transmission, lift the front of the engine straight up as the transmission clears the vehicle's bottom.
Remove the transmission mount and cross member.
Final Lifting and Transport:
Center the crane boom over the engine and lift it slightly.
Ensure the engine is securely fastened and all connections are removed.
Raise the engine while pulling it forward, avoiding any binding or damage.
Once clear of the vehicle, move the crane and engine away.
Lower the engine close to the floor for transport to the work area.
Post-Removal Steps:
If the transmission was removed with the engine, remove the bell housing bolts and inspection plate bolts.
For automatic transmissions, remove the torque converter-to-flexplate bolts.
Use a C-clamp to secure the torque converter and mark its position relative to the flexplate.
Engine Disassembly
Mounting the Engine:
Raise the engine and position it next to an engine stand.
Mount the engine to the stand using appropriate bolts, ensuring it's supported by at least four bolts that fit securely.
Position the engine so its center is in the middle of the stand's adapter plate for balanced rotation.
In most cases, remove the flywheel or flexplate to mount the engine; mark its position on the crankshaft for reassembly.
Loosen the flywheel bolts in a star pattern to avoid distortion of the flywheel.
Flywheel Handling:
Use a flywheel lock to prevent rotation while loosening bolts.
Support the flywheel while removing the bolts to prevent injury or damage due to its weight.
Inspect the flywheel for damage and signs of clutch problems.
Disassembly Procedure:
Once mounted, remove the sling or lifting chain.
Refer to the service manual during disassembly.
Disassemble slowly, inspecting each part for damage, wear, overheating, and leaks.
Cylinder Head Removal
Initial Steps:
Remove the intake and exhaust manifolds; on some inline engines, they may be removed as an assembly.
Remove the valve cover(s) and disassemble rocker arm components following manufacturer guidelines, checking for sludge.
OHC Engine Considerations:
Remove the timing belt cover to access the timing belt or chain and sprockets.
Check the alignment of timing marks on the crankshaft and camshaft sprockets; note any misalignment.
Be aware of interference engines where valves can hit pistons if the timing belt fails.
Replace the timing belt at specified intervals to prevent damage.
Belt/Chain Removal:
Remove the belt or chain by moving the tensioner pulley to relieve tension.
Component Organization:
Keep pushrods, rocker arms, and rocker arm assemblies in order using an organizing tray or labeled markers to aid diagnosis.
Remove lifters from the block and keep them in order.
Cylinder Head Bolt Removal:
Loosen cylinder head bolts in a specified sequence, typically the reverse of the tightening sequence.
If no specific sequence is given, loosen bolts gradually, starting from the ends and working toward the center.
Remove the bolts and lift off the cylinder head.
Final Steps:
Save the cylinder head gasket for comparison during reassembly.
Protect the cylinder head(s) by setting them on a soft surface.
Remove the water pump.
Invert the engine block and remove the oil pan, checking for metal shavings and sludge.
Cleaning Engine Parts
Importance of Cleaning:
Thorough cleaning is essential after disassembly and before inspection or machining.
Incorrect cleaning methods or agents can cause damage.
For example, caustic soda can dissolve aluminum parts.
Caustic soda is a strong detergent found in carbon-removing solvents.
Types of Contaminants:
Water-soluble soils (dirt, dust, mud).
Organic soils (petroleum by-products, combustion by-products, coatings).
Rust (from exposure to oxygen and moisture).
Scale (mineral deposits from heated water).
Cleaning with Chemicals
Processes:
Chemical cleaning uses chemical action to remove dirt, grease, scale, paint, and rust.
Traditional chemicals may have health risks (skin exposure, inhalation) and be flammable.
Alternatives:
Water-based nontoxic chemicals reduce risks and may be biodegradable.
Contaminated cleaning solutions become hazardous waste requiring special disposal.
Some manufacturers offer waste-handling and solvent recycling services.
Chemical Cleaning Machines
Parts Washers:
Widely used and inexpensive for removing grease, oil, and dirt.
Methods include soaking, agitation, solvent streams, and spray gun applicators.
Soak Tanks:
Cold soak tanks are used for carburetors, throttle bodies, and aluminum parts.
Hot soak tanks heat the solution to temperatures ranging from 160^\circ F to 200^\circ F (71^\circ C to 93^\circ C), often large enough for an entire engine block.
Agitation speeds up cleaning by shaking grime loose and penetrating crevices.
Hot Spray Tanks:
Operate like automatic dishwashers, using hot jet sprays to clean parts.
Thermal Cleaning
Process:
Uses heat to bake off or oxidize dirt and contaminants.
Cleaning furnaces operate at temperatures generally from 650^\circ F to 800^\circ F (343^\circ C to 426^\circ C).
Oils and grease are reduced, leaving a powdery ash.
The ash must be removed by shot blasting or washing.
Advantages:
Total reduction of oils and grease.
More environmentally acceptable than chemical cleaning.
Offers easier cleanup with shot blast or glass beads.
Abrasive Cleaners
Application:
Abrasive cleaning is often used with other cleaning processes.
Cleaning by Hand:
Manual cleaning is sometimes necessary.
Use scraping or wire brushing to remove heavy buildup.
Clean aluminum and soft metals carefully.
Techniques:
Steel or plastic scrapers are used to remove old gasket material.
Power tools with sanding discs (emery cloth) are also used.
Carbon Removal:
Carbon can be removed with wire brushes or wheels driven by electric or air drill motors.
Gallery Cleaning:
Oil galleries must be cleaned by hand, using brushes soaked in cleaning solvent after removing gallery plugs.
Abrasive Blaster
Application:
Compressed air shot and grit blasters are used on parts that will be machined after cleaning.
Types of Media:
Shot (round) and grit (angular).
Process:
Parts must be dry and grease-free.
Media Types and Effects:
Steel shot and glass beads are used for cleaning and/or peening (increased resistance to fatigue and stress).
Steel shot is normally used with airless wheel blast equipment.
Glass beads are blown through a nozzle by compressed air in an enclosure.
Grit is used for aggressive cleaning or etching.
Cautions:
Grit removes metal, which can change tolerances.
Grit blasting can create pits where pollutants can settle, leading to stress corrosion.
Grit should not be used for peening.
Parts Tumbler
Application:
Used for cleaning small parts like engine valves.
Various cleaning media can be used.
Saves hand labor and eliminates dust.
Vibratory Cleaning
Process:
Uses a vibrating tub filled with ceramic, steel, porcelain, or aluminum abrasive to scrub parts.
Solvent is flushed through the tub and filtered.
Alternative Cleaning Methods
Ultrasonic Cleaning:
Uses high-frequency sound waves to create microscopic bubbles to loosen soil.
Minimizes chemical content.
Citrus Chemicals:
Citrus-based cleaning chemicals are being developed as replacements for hazardous solvents.
Salt Bath:
Uses high-temperature molten salt to dissolve organic materials.
Crack Detection
Causes of Cracks:
Cracks result from stress or strain.
Stresses can be caused by pressure or temperature changes during casting.
Fatigue from repeated stress cycles also leads to fracturing a thin-walled casting.
Impacts, flexing, excessive overheating, or sudden cooling can also cause cracking.
Detection Methods:
Visual inspection.
Specialized equipment for suspected cracks.
Pressure Checks: Coolant passages are plugged, air is injected, and the block/head is submerged in water to check for bubbles.
Crack Detection Methods
Magnetic Checks:
Magnetic Particle Inspection (MPI) uses a magnet to create a magnetic field in a cast iron unit.
Iron filings are sprinkled on the surface to detect a secondary magnetic field resulting from a crack.
The magnet must be rotated and the metal checked in both directions since the secondary magnetic field will not form if the crack is in the same direction as the magnet.
Die Penetrant:
Uses penetrant, cleaner, and developer.
Follow this sequence:
Spray penetrant onto the surface.
Wait 5 minutes.
Spray cleaner onto a clean cloth.
Wipe off visible penetrant.
Spray developer on the tested area.
Wait until the developer is totally dry.
Inspect for red lines indicating cracks.
Crack Repair: Decide to replace or repair, considering cost.
Engine Reassembly
General Rule: The sequence is essentially the reverse of disassembly.
Consult Service Manual: Always refer to the service manual during reassembly.
Installing The Engine
Complexity: Installing a computer-controlled engine can be complex.
Referring to the vehicle’s service manual is absolutely essential for this procedure.
General rule: Typically the procedure is the reverse of the removal procedure.
Summary
Service Manual: To prepare an engine removal and disassembly (as well as reassembly and installation), it is important to always follow the specific service manual procedures for the particular vehicle being worked on.
Cleaning: An understanding of specific soil types, chemical types, cleaning machines, and cleaning methods can save time and effort during the engine cleaning process.
Crack Detecting: There are three common methods for detecting cracks in the metal casting of engine parts: using a magnet and magnetic powder (iron filings), using penetrant dye (especially for aluminum heads and blocks), and pressuring with air.