Inspection of engine components is necessary after the engine is dismantled. The various parts are inspected in this process. In this article, I will discuss the components of the engine that need to be inspected.
Inspection of Engine Components
The inspection procedure is detailed in the following paragraphs and covers the complete overhaul of the engine with that unit taken out of the vehicle. Before commencing the inspection and repair operations, the following inspections should be kept in mind.
> During and immediately after disassembly, inspect the cylinder block and head for evidence of water leakage or damage after washing them clean, inspect more closely.
> Wash and clean all the disassembled parts. Remove the grease and the carbon particles. Be sure to the dirt and clean the passages of the water jackets.
> Use compressed air to clean internal engine oil holes and passages.
> Do not disturb the sets of combinations of valves, bearings, bearing caps, etc.
The other important components of the engine are discussed in the article below.
Cylinder Head
The cylinder head needs to be examined in a proper manner. The process is-
> Remove all the carbon from the combustion chamber.
> Check the cylinder head for cracks in the intake and exhaust ports, combustion chamber, and head surfaces.
> Check the flatness of the gasket surface. For checking the surface location use the perfect tool recommended by the owner guide. If the distortion limit of 0.05 mm is exceeded, correct the gasket surface plate using an abrasive paper of about 400(waterproof silicon carbide abrasive paper). Place the paper over the surface plate and rub the gasket surface to grind off the uneven spots. Should this fall to reduce the thickness gauge readings within the limit, replace the cylinder head. Leakage of the combustion gases from the gasket joint often occurs due to a wrapped gasket surface. Such leakage results in a reduced power output.
> Check the flatness of the manifold seating faces.
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| Check the seating faces of the cylinder head. |
> Check the seating faces of the cylinder head for manifolds, using a straight-edge and thickness gauge, in order to determine whether these faces should be corrected or the cylinder head replaced.
Rocker Arm
If the tip of the adjusting screw in the rocker’s arm is badly worn, replace the screw. If the rocker is worn then it is advisable to replace it with the new one. Visual examine each rocker arm spring for any evidence of breakage or weakening. Be sure to replace the spring found in bad conditions.
Check the rocker arm shaft for any wear and deflation. If the rocker arm shaft is worn, replace it. The increase of the wear is dependent on the basis of two readings. The first one is taken on the rocker arm ID, and the other is taken on the shaft diameter.
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| Measuring rocker arm id and shaft |
If the deflection happens set the rocker shaft between V blocks, and measure its deflection by using a dial gauge. If the measured deflection exceeds the specific limit of 0.12 mm, replace the shaft.
Rocker arm measurement table
| Item. | Standard. | Limit. |
|---|---|---|
| Rocker arm ID. | 14.985-15.005 | mm. |
| Rocker arm shaft diameter. | 14.965-14.980 | mm. |
| Arm to shaft clearance. | – | 0.07mm. |
Camshaft
A noisy engine or engine not producing enough power frequently has an excessively worn-out camshaft or a camshaft that is bent or bowed. The wearing often occurs on the cams and the journals of the camshaft.
a. Cam wear
Use a micrometer to measure the cam wear. Measure the height of each cam. If the measured height is below its limit replace the camshaft. The height table is below-
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| Measuring cam height. |
| Cam height(H). | Standard(mm). | Limit(mm). |
|---|---|---|
| Inlet cam. | 36.152 | 36.100 |
| Exhaust cam. | 36.152 | 36.100 |
| Pump drive cam | 33.300 | 33.00 |
b. Deflection
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| Measuring cam shaft deflection. |
Set the camshaft between two V blocks, and measure its deflection by using a dial gauge. If the measured deflects the specific limit of 0.10 mm then replace the camshaft.
c. Journal Wear
Check the camshaft journal and camshaft housing for pitting, scratches, wear, or damage. If any wear is found then replace the camshaft or the cylinder head.
Use a micrometer, to measure the journal diameter in two directions at four places to obtain four readings on each journal, and check the journal bores with a cylinder gauge producing four readings on each. From this reading compute the journal clearance. This clearance is also called as the radial clearance.
If the computed radial distance exceeds specific limits, replace both the camshaft and the cylinder head.
d. Thrust Clearance
Use a thickness gauge to measure the thrust clearance. If the measured clearance exceeds specific limits, replace the thrust plate or camshaft.
Valve Guides
Use a micrometer or a bore gauge, to take diameter readings on valve stems and guides to check the stem-to-guide clearance. Check carefully each stem and guide. If the clearance exceeds the limit replace the valves and the valve guides. See the table below for the specific value.
If the bore gauge is not available, check the end deflection of the valve stem with a dial gauge. If the deflection exceeds its limit replace the valve stem and valve guide.
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| Measuring valve stem diameter. |
| Item. | Inlet. | Exhaust. | Limit. |
|---|---|---|---|
| Valve stem diameter. | 6.965-6.980 mm | 7.000-7.015 mm | – |
| Valve guides ID. | 7.000-7.015 mm | 7.000-7.015 mm | – |
| Stem to guide clearance. | 0.020-0.050 mm | 0.035-0.050 mm | 0.09 m |
Valves
Valves used in engines should be examined in the following manner-
- Remove all carbons from the valve.
- Inspect each and every valve for wear or distortion. If need to change then change the valve.
- Measure the thickness of the valve head. If the inlet valve thickness exceeds 0.6 mm and the exhaust valve thickness exceeds 0.7 mm then replace it.
- Inspect the valve stem end face from pitting and wear. If any pitting or wear is found in the valve stem end may be resurfaced, but not so much as to grind off its chamber. When it is worn so much that its chamber is gone, replace the valve.
- check each valve with a dial gauge. To check runout, rotate the valve slowly. If the measured runout exceeds the limit, i.e.,n 0.08 mm/0.003 in., replace the valve.
a. Seating contact width
Produce a contact pattern for each valve in the usual manner, that is, by giving a uniform coat of red-lead paste to the valve seat and by rotating and tapping each seat with the valve head. The valve lapper must be used for this purpose.
The pattern produced on the seating face of each valve must be a continuous ring without any break, and the width of the pattern must be within the following specifications.
Inlet – 1.3-1.5 mm
Exhaust – 0.51-0.059 mm.
b. Valve seat repair
A valve seat does not produce uniform contact with its valve or show seating contact that is off the specified width and must be repaired by regrinding or by cutting and regrinding and finished by lapping.
c. Exhaust valve seat
A valve seat cutter marks the three lines on the exhaust valve. Three cutters must be used, the first for making the 15^0 angle, the second for making the 75^0 angle, and the third for making the 45^0 seat angle. The third cut must be made to produce the desired seat width.
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| Valve seat angel |
d. Intake valve seat
For the cutting of the intake valve and the exhaust valve, the sequence can be the same but the cutting angle will be different.
e. Valve lapping
Lap the valve on the seat in two steps, first with a coarse-size lapping compound applied to the face and the second with a sizing compound, each time using a valve lapper according to the usual lapping method.
Valve Springs
Inspections of valve springs are carried out in the following manner-
> Check the sound condition of each spring, free of any evidence of breakage and damage. Remember weakened valve springs can cause chatter, not to mention the possibility of reducing the power output due to gas leakage caused by decreased setting pressure.
> Use a square and surface plate to check each spring for a sequence in terms of the clearance between the end of the valve spring and the square. Valve springs are given the extra clearance of 2.0 mm, and must be replaced.
Cylinder Block
The following checks are done for the checking and inspection of cylinder block-
a. Distortion of gasket surface
Use a straightedge and a thickness gauge, check the gasketed surface for distortion, and if the flatness exceeds the prescribed limit of 0.05 mm., correct it.
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| Measuring cylinder bore. |
b. Honing or reboring cylinders
> Inspect cylinder walls for scratches, roughness, or ridges that indicate excessive wear. If the cylinder bore is very rough deeply scratched, or ridged, rebore the cylinder and use an oversized piston.
> Using a cylinder gauge, measure the cylinder bore in thrust and axial direction at the tree positions.
If any of the following conditions are noted, rebore the cylinder-
- The cylinder bore diameter exceeds the limit.
- Cylinder measurements at two positions exceed tapper limits.
- The difference between the thrust and radial-axial measurements exceeds the out-of-round limit.
Note – If any of the cylinders have to be rebored, rebore the three to the same next oversize. This is important for engine safety.
Pistons
The instructions below should be followed while inspecting the piston-
> Inspect the pistons for faults, cracks, or other damages. Damaged or faulty pistons should be replaced.
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| Measuring piston diameter |
> Check and measure the piston diameter. The piston diameter should be measured at a position 30 mm, from the piston skirt end in the direction perpendicular to the piston pin.
> Measure the piston clearance. Measure the cylinder bore diameter and the piston diameter to find their differences, which gives the piston clearance. Piston clearance should be within the specified limit of 0.04. If the piston clearance does not match the specifications, rebore the cylinder and use an oversized piston.
> Before finishing the checking, first ensure that the piston grooves are clean and dry. Fit the new piston ring to the piston groove, and measure the clearance between the ring and the ring land by using a thickness gauge.
a. Piston Rings
To measure the end gap, insert the piston ring into the cylinder bore with the specified tool and then measure the gap by using a thickness gauge. If the measured gap is higher than the 0.03-0.07 mm., then replace the ring.
Note- Clean the top of the cylinder bore before inserting the piston ring.
b. Piston Pin
First check the piston pin, the connecting rod’s small end bearing, and the piston bore for wear or damage, paying particular attention to the condition of the small end bearing bush. If the pin, connecting rod small end bearing, or piston bore is damaged, replace the pin, connecting rod, or piston.
> Carefully check the pin clearance in the small end. Replace the connecting rod if its small end is badly worn or damaged or if the clearance exceeds the limits as shown in the table below-
| Name. | Standard. | Limit. |
|---|---|---|
| Piston clearance in the small end. | 0.003-0.016 mm. | 0.05 mm. |
| Small end bore | 16.003-16.001 mm. | – |
| Piston pin dia. | 15.995-16.000 mm. | – |
Connecting Rod
The following checks are advisable to follow when inspecting the connecting rod-
a. Big-end clearance
Check the big end bearing of the connecting rod, for side clearance, with the rod fitted and connected to its crank pin in the normal manner. If the measured clearance is found to exceed its limit(0.30 mm.) replace the connecting rod.
b. Connecting rod alignment
Mount the connecting rod on the aligner to check it for a bow and twist. If the limit is exceeded, replace it. These limits are-
- Limit on bow – 0.05 mm.
- Limit on twist – 0.10 mm.
Crank Pin and Connecting Rod Bearings
Inspection of the crank pin and the connecting rod bearings are carried out in the following ways-
> Check the crank pin for any wear or damage. Measure the crank pin for out-of-tapper or taper with a micrometer. If the crank pin is damaged, or the round-of-round or taper is out of limit, replace the crankshaft or regrind the crank pin to the under-size bearing. See the table for details –
| Connecting rod bearing size. | Crank pin diameter(mm). |
|---|---|
| Standard twist. | 37.985-38.000 |
| 0.25 mm under-size | 37.735-37.750 |
| Limit on twist. | 0.50 under-size |
| Out-of-round and taper limit. | 0.0 |
> Inspect the rod bearing. Inspect the bearing shells for signs of fusion, pitting burn, or flanking and observe the contact pattern. If the bearing shells are found in a defective condition, they should replaced. Two kinds of rod bearings are available- the standard size bearing and the 0.25 mm. undersize bearing.
> Check the rod bearing clearance. Clean the bearing and the crank pin, then check the rod bearing clearance. Install the bearing in the connecting rod and the bearing cap. Place a piece of gaging plastic along the full width of the crank pin as contact by the bearing(Paralla to the crankshaft), avoiding the oil hole.
> Install the rod bearing cap on the connecting rod. When installing the cap, be sure to point the arrow mark on the cap to the crankshaft pully side. after applying engine oil to the rod bolts, tighten the cap nuts to the 28-32 nm torque. Do not turn the crankshaft with the gaging plastic installed.
> Remove the cap using a scale-gaging plastic envelope, and measure the gaging plastic width at the width point.
> If the clearance can not be brought to within its limit even by using a new standard size bearing, regrind the crank pin to undersize and use a 0.25 mm undersize bearing.
Crankshaft
Check and follow the following steps to check the crankshaft-
a. Crankshaft runout-
Using a dial gauge, measure the runout at the central journal. Rotate the crankshaft slowly. If the measurement exceeds its limit of 0.06 mm, replace the crankshaft.
b. Crankshaft thrust play-
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| Crankshaft thrust play |
Measure the crankshaft thrust play with the crankshaft set in the cylinder block in the normal manner, that is, with the thrust bearing and the journal bearing caps installed. Tighten the bearing caps bolts to the 43-48 nm torque. with a dial gauge, we read the displacement in the axial(thrust) direction of the crankshaft. If there are any certain problems found then change the crankshaft.
c. Out-of-round and taper of journals-
A badly worn crankshaft journal shows up as a difference in diameter at a cross-section or along its length. The difference is determined by taking micrometer readings. If any of the journals are badly damaged or if the amount of uneven wear in the sense explained in the proceeding paragraph exceeds the limit, regrind or replace the crankshaft.
Limit on runout or tapper 0.01 mm.
Main Bearings
The main bearings should be checked for pitting, wear, or damage. If any wear or damage is found, both the upper and lower halves are replaced. One-half of the bearing is never replaced without replacing the other half. Check the main bearing clearance using a gaging plastic according to the following procedure-
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| Measuring main bearing clearance |
> Remove the bearing and the main caps.
> Clean the bearings and the main journals.
> Place a piece of gaging plastic along with the entire width of the bearing(parallel to the crankshaft) on the journal, avoiding the oil hole.
> Install the bearing cap as previously specified and evenly tighten the cap bolts to the specified torque. The bearing cap must be torqued to specifications in order to ensure the proper reading of clearance.
Note- Do not rotate the crankshaft while the gaging plastic is installed.
> Remove the cap and using a scale on the gaging plastic envelope, measure the gaging plastic width at its widest point. If the clearance exceeds its limit, replace the bearing. Always replace both the upper and lower inserts as a unit.
A new standard bearing may produce the proper clearance. If not, it will be necessary to regrind the crankshaft journal for the use of 0.25 mm., undersize breaking. After selecting the new bearing, recheck the clearance.
Rear Oil Seal
Carefully inspect the oil seal for wear or damage. If the lip is worn or damaged, replace it.
Flywheel
The flywheel should be inspected as follows-
> If the ring gear is damaged, replace the flywheel.
> If the surface in contact with the clutch disc is damaged, or excessively worn, replace the flywheel.
> Check the flywheel for face runout with a dial gauge. If the runout exceeds the limit of 0.02 mm., replace the flywheel.
Ending up with
Checking the engine parts and the procedure of inspection needs a perfect hand in the automobile sector. The prime engineer can do this work without any instructions.
I hope you will like this article.
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