There are different types of automobile engines, and the disassembly and repair methods are different.
Take the example of the engine of a mini-car.
1) Remove the engine access cover on the cabin floor and remove the wing under the engine.
2) Remove the drain plugs on the radiator and cylinder head respectively to drain the coolant.
3) Disconnect the connecting wire between the engine and the battery, then disconnect the water temperature sensor wire, and remove the alternator electrode connector.
4) Disconnect the fuel pipe and heater pipe on the fuel pump housing, and disconnect the throttle cable and choke cable from the carburetor.
5) Remove the leak circulation system hose from the cylinder head cover, and disconnect the heater return and outlet hoses.
6) Disconnect the hose from the thermostat coverat and remove the air filter assembly.
7) Disconnect the fuel return hose from the carburetor and the radiator outlet hose.
8) Disconnect the lubricating oil pressure sensor wire (yellow/black) and remove the wire nut.
9) Disconnect the clutch cable from the engine installation part and the clutch lever. Remove the muffler from the exhaust manifold and frame, then remove the driveshaft.
10) Disconnect the speedometer flex shaft from the transmission, disconnect the reverse light switch connector, and disconnect the pull rod on the transmission shift rocker arm.
11) Disconnect the starter motor (black/yellow) and (+) pole wires and disconnect the battery ground (-) pole wire from the transmission case.
12) Remove the lower radiator guard and support the engine and transmission.
13) Remove the mounting bracket fromthe frame's transmission and engine mounting bracket.
14) After removing all the connecting parts around the engine, remove the engine avoiding any contact between the cooling fan and the protection plate.
2. How to disassemble the engine of Songhuajiang mini car
1) Remove the starter and transmission from the engine.
2) Unscrew the oil pan drain plug and drain the lubricating oil.
3) Use special tools to remove the clutch cover.
4) Remove the distributor assembly.
5) Remove the fuel pump.
6) Remove the gearbox from the distributor.
7) Remove the cooling fan.
8) Remove the alternator; Remove the alternator mounting bracket plate.
9) Remove the thermostat cover.
10) Use a special tool to block the flywheel and remove the crankshaft pulley.
11) Remove theouter cover of synchronous belt; remove the synchronous belt tensioner assembly and remove the synchronous belt.
12) Use special tools to fix the camshaft and remove the timing gear on the camshaft; remove the timing gear on the crankshaft;
13) Remove the synchronous gear positioning key, then remove the synchronous toothed belt retaining ring and inner cover.
14) Remove the front camshaft support cover from the cylinder head and remove the water pump.
15) Remove the heat shield line from the manifold, remove the exhaust manifold and heat shield liner.
16) Use special tools to remove the oil filter. When removing the oil filter, do not allow oil to splash.
17) Remove the intake manifold and remove the water inlet hose bracket.
18) Remove the cylinder head cover. Ofstighten the 8 valve adjusting screws, unscrew the 10 screws securing the rocker arm shaft, remove the rocker arm shaft, remove the rocker arm and rocker arm spring, remove the camshaft thrust plate and remove the camshaft from the front end of the cylinder. leave.
19) Remove the cylinder head, use a special tool to press the valve spring, remove the valve circlip, then remove the valve spring and valve, remove the flywheel and valve bracket 'alternator and remove them from the bracket; cylinder block Remove the front engine suspension supports (left and right); remove the oil pan and oil filter.
20) Remove the connecting rod covers from the 2nd and 3rd cylinders, and remove the connecting rod piston assembly from the cylinder body on the cylinder head side of the cylinder block. Remove the connecting rod piston assembly from cylinders 1 and 4 in this manner; remove the crankshaft rear oil seal cover and oil pump assembly;remove the bearing cover from the crankshaft main journal and carefully remove the crankshaft, remove the piston from each piston; Pin the circlip and push in the piston pin.
3. How to disassemble the cylinder head of a mini car engine
Among mini cars, the cylinder heads of Tianjin Xiali, Huali, Changan and Alto cars are all made of cast aluminum. pieces. There is a gap between the engine and the body. The space is small, and the hardness of cast aluminum parts is worse than that of cast iron parts. When disassembling the cylinder head, be sure to follow the following order:
1) Drain the engine coolant, remove the oil pipe and vacuum pipe, and clean the air. Remove the connector tube and throttle cable.
2) Remove the cylinder head cover and disassemble the water outlet pipe.
3) Remove the water pump drive belt and fan drive belt, then removefit the intake and exhaust manifolds.
4) Remove the upper and lower timing belt covers and the timing belt tensioner.
5) Remove the timing belt. Before removing the timing belt, mark the back of the timing belt to indicate its normal direction of rotation. Avoid getting water or oil on the toothed belt during disassembly.
6) Remove the distributor and distributor base, gradually loosen the cylinder head mounting bolts evenly from both ends to the center in 2-3 times, and remove the cylinder head assembly.
4. How to Repair a Mini Car Engine Cylinder Head
(1) Remove carbon deposits from the cylinder head. Carbon deposits appear on and around the surface of the combustion chamber. the exhaust pipe, which will cause overheating and a reduction in engine power, it will therefore be necessary toAlso remove carbon deposits from the valves. Use chemical reagents to clean carbon deposits or use a scraper to remove carbon deposits; when removing carbon deposits, do not scratch the metal surface or use sharp tools.
(2) Check the flatness of the cylinder head surface. Use a ruler and feeler gauge to check flatness in 6 directions. The flatness of the cylinder head assembly surface is 0.05 mm. If the measured value exceeds the specifications, place 400# sandpaper on the platform so that the surface of the cylinder head faces the sandpaper, and move the cylinder head to grind and cut. the flatness of the surface. If the conditions are still not met, replace the cylinder head.
(3) Check the flatness of the exhaust manifold seat surface, and use a ruler and feeler gauge to check the cylinder.Cover the surface of the exhaust manifold seat assembly. The surface flatness of the entire exhaust manifold seat is 0.1mm. If the measured value exceeds specifications, it must be repaired or replaced. The flatness limits, maintenance methods and requirements of the intake manifold seat are the same as those of the exhaust manifold seat.
5. How to prevent deformation of the cylinder head of Songhuajiang mini car engine
When installing the cylinder head, first clean the joint surface of the cylinder block and cylinder head, and check whether The head gasket is intact. Then install the head gasket to the cylinder block, check for oil, water and other debris in the cylinder head bolt mounting holes on the cylinder block and blow them out with compressed air. Carefully install the cylinder head onto the head gasket to avoid scratching the gasket.
Insert the cylinder head bolts into the bolt mounting holes and tighten the bolts evenly and gradually from the center to both ends to the specified torque. The cylinder head tightening torque is: 53.9-58.8 N·m for Songhuajiang Automobile; 53.9-63.7 N·m for Xiali and Huali sedans; .
6. How to repair the cylinder block of Songhuajiang mini car engine (1) Inspection of the flatness of the upper end surface of the cylinder block The method of inspection of the flatness of the block cylinders. the upper end surface of the cylinder block is consistent with the surface plane of the cylinder head. The flatness inspection method is the same, and the limit value for the flatness of the upper end face of the cylinder block is 0.05mm. If the measured value exceeds the above specifications, it must be repaired or replaced.
(2) For cylinder maintenance, use a cylinder gauge to measure thee diameter of the cylinder at three positions at the top, middle and bottom of the cylinder, in the longitudinal and transverse directions. between the maximum value and the minimum value determines the diameter of the cylinder if the change in size exceeds the limit. If the limit is exceeded or the cylinder wall has been severely scratched or damaged, use a larger number of pistons.
Add a large amount to the piston
Level I
0.25 mm
Level II< / p>
0.50 mm
If one of the four cylinders is enlarged in diameter, the remaining three cylinders must be enlarged accordingly to ensure that the diameters of the four cylinders are the same.
When replacing the piston, the maximum limit of the difference between the maximum diameter and the minimum diameter of the cylinder is 0.05 mm. The gap between the piston and the cylinder should be between 0.04 and 0.06 mm. The gap between the piston and the cylinder is equal to the diameter of the cylindre minus the cylinder diameter, excluding the piston diameter, the piston diameter is measured in the direction perpendicular to the axis of the piston pin and at the same height as the center of. the pin hole, approximately 30mm from the end of the piston skirt. The value of the piston diameter
Piston diameter/mm
Standard size
61.95-61.99
Extra size
62.20-62.24
62.45-62.49
7 . How to repair the cylinder gasket
(1) Determine whether the cylinder gasket is burned When the following phenomena occur, you need to determine whether the cylinder gasket is burned: ① The connection between the cylinder head and. the cylinder blockThere are partial air leaks at the seams. ② Engine power decreases. When the cylinder seal is seriously damaged, the engine cannot start and run. ③If there is a layer of engine oil floating on the water surface in the radiator, this means that the cylinder seal has been blown between the oil passage and the water passage. ④ If carbon deposits form in the cylinder head bolt holes and on the bolts, it means that the cylinder gasket has been burned out at the cylinder port and the cylinder head threaded port. ⑤ If there is thick white smoke and a small amount of blue smoke and water vapor in the exhaust, it means that the cylinder gasket has been burned somewhere between the cylinder mouth and the water channel.
(2) Determine whether the cylinder seal is well sealed, open the radiator cover, fill the radiator with cooling water, and let the engine run at medium speed. At this point, observe the internal conditions of the radiator. If bubbles continue to emerge, this indicates that the cylinder seal is not properly sealed. The more bubbles, the worse the leak will be. When the cylinder seal eIf seriously damaged, apply lubricating oil around the gasket between the cylinder head and the cylinder block and observe the gasket. If bubbles appear, this means that the seal of the cylinder seal is failing and a new seal must be replaced. replaced.
(3) Replace the cylinder seal. Once the cylinder seal is damaged, it should be replaced in time. The cylinder gasket should be replaced when the car is cold. The replacement steps are as follows: ① Remove the cylinder head. ② Check whether there are depressions, bulges, cracks or damage on the cylinder seal surface. No chips are allowed between the covering material and the frame. ③ Before installing the cylinder gasket, clean the old gasket and dirt on the gasket surface of the cylinder block and cylinder head, check whether there are irregularities, cracks and other defects on the two gasket surfaces, then install the gasketcylinder on the cylinder block. ④Install the cylinder head and tighten the cylinder head bolts in the specified order to the specified torque. ⑤Install the timing belt and rotate it in the original direction according to the brand.
8. How to judge whether the piston can continue to be used
Check the gap between the piston and the cylinder. Measure the diameter of each cylinder at 6 points. For example, in Xiali cars, it must be ensured that the difference between the maximum diameter and the minimum diameter of each cylinder does not exceed 0.1mm, otherwise the cylinder must be repaired. Measure the outer diameter of the piston 30mm from the bottom of the piston for Songhuajiang mini car and Alto car, 15mm for Xiali car, 17mm for Huali car and 8-10mm for Wuling car. Calculate the piston-to-cylinder clearance based on the measurements above. The gap between the piston and the cylinder is specified: Songhuajiang mini car is 0.04-0.06mm; the carre Alto is 0.045 to 0.055 mm; Huali car is 0.045-0.12mm; mm. If the measured deviation does not exceed the specified value, the piston can continue to be used.
The piston pin hole, piston ring and corresponding clearance between the piston ring and the ring groove do not exceed the permitted value and can continue to be used.
The matching clearance between the piston pin hole and the piston pin, and between the piston ring and the ring groove, has exceeded the allowable value. However, after replacing the new piston pin and piston ring, the match occurred. The relationship can still meet the technical requirements, the piston can still be used.
9. How to replace the engine piston
When replacing the engine piston, you must use the same level and type of piston. Choose the same size piston and piston pin to guarantee the clearance of myrequired.
Use special tools to assemble the connecting rod and piston. Insert the spring and long rod into the main body and install the spacer onto the main body with the notched side up. Install the piston on the main body, align it with the notch on the pad, and inject engine lubricating oil into the piston pin hole. Insert the lubricated piston pin into the piston pin hole. Align the small end of the connecting rod with the hole in the piston pin, so that the front mark of the piston and the front mark of the connecting rod are in the same direction, and push the piston pin through the small rod installed on the piston. pin.
Use caution when installing the piston rings to avoid scratching the piston at the open end of the side ring. Position each piston ring opening 120° from the open end of the oil ring liner in the directionopposite each other to ensure that no two piston ring openings have the same angle around the circumference of the piston. Apply lubricating oil to the piston skirt, piston rings and piston pins, and ensure that the open end of the piston ring does not move during operation. Coat the cylinder wall, the upper bearing surface of the connecting rod and the diameter of the connecting rod shaft with lubricating oil, use a ring press to compress the piston ring, and then install the piston into the cylinder depending on the mark on the piston.
When replacing the piston, try to use a piston of the same size. The corresponding clearance between the piston and the cylinder should be basically the same as that of the other cylinders without replacing the piston. The tightness of the piston pin and the pin seat hole should be loosened appropriately according to the use of the moto ensure that it is consistent with the tightening of the other cylinders.
10. How to check piston ring clearance
(1) Check piston ring side clearance Use a feeler gauge to measure the side clearance of each piston ring in the groove. If the gap is measured, when the limits shown in Table 2-3 are exceeded, measure the groove width and piston ring thickness to determine whether the piston or piston ring needs to be replaced.
Piston ring thickness, ring groove width (mm)
Piston ring thickness
First ring
1 .47-1.49
Two rings
1.47-1.49
Oil ring
0.45
Ring groove width
First ring
1.53-1.55
Second ring
1.52-1.54
< p>Oil ring
2.81-2.83
(2) Check piston ring opening Gap mMeasuring and inspecting the piston ring opening space. Place the piston ring into the cylinder and level the piston ring with the top of the piston inverted until it is 110mm from the head gasket mounting surface, then measure the opening gap of the piston ring.
If the opening clearance exceeds the limit specified in the table, replace the entire piston ring set. For a cylinder, if any of the first, second or wiper blades are defective, all piston rings must be replaced as a group.
11. How to Properly Install Piston Rings
Micro car oil rings use a combination of two side rings and one packing ring. The surface of the side ring of the wiper ring in contact with the cylinder is chrome-plated like the first and second rings, and the other surfaces are phosphated; the coating ring is soft nitrided;
Wheninstallation, the side with the manufacturer's mark should face up, and install the piston oil ring first. Install the packing ring into the oil ring. When installing the trim ring, do not make the open end of the trim ring coincide with the front mark, then install the upper side ring. Be careful that the open end of the side ring does not scratch the piston and deflect the open end of the upper side ring 90° to the left relative to the open end of the side ring. When installing the lower side ring, its open end deviates 90° to the right from the open end of the support ring. Then install the first and second piston rings so that each opening of the piston ring is 120° from the open end of the oil ring in opposite directions to ensure that no opening of thepiston ring does not have the same angle around the circumference of the piston.
12. How to inspect the crankshaft
The crankshaft inspection of Songhuajiang mini vehicle is carried out as follows:
(1) Crankshaft bending inspection, measure the crankshaft number. The circular runout of the third main journal (middle), the limit of the circular runout of the main journal of the crankshaft is 0.06mm. If the measured value exceeds the limit, the crankshaft must be repaired or replaced.
(2) Check the crankshaft axial thrust clearance. Install the crankshaft bearing ring and thrust adjustment ring into the cylinder body, then install the bearing cap. Tighten to 43.0-48.0 N·m. the bolts to the tightening torque. As shown in Figure 2-32, use a micrometer to measure the axial movement of the crankshaft. The standard clearance is 0.1-0.3mm and the limit is 0.4mm. If the measurement exceeds thelimit, the thrust adjustment trim must be replaced with an enlarged or Class II adjustment trim.
Thickness of the crankshaft thrust adjustment pad
Thickness of the crankshaft thrust adjustment pad
Standard
Level
Size/mm
Ⅰ
2.4-2.5
Ⅱ
2.5-2.6
Enlarge
2.6-2.7
(3) Check the crankshaft journal for wear and tear. connecting rod journal. On each main journal and connecting rod journal, take 4 points to measure the outside diameter. The measurement should be carried out over the entire surface of each journal, and the oil hole on the journal should be avoided. Based on each measurement result of the main journal and the connecting rod journal, the difference between the maximum value and the minimum value is calculated, that is, the degree of uneven wear. The uneven wear limit is 0.01 mm. The crankshaft journal and the touconnecting rod ring are very worn or have exceeded the limit. The crankshaft needs to be repaired or replaced.
13. How to inspect the crankshaft main bearing
The inspection of the crankshaft main bearing of Songhuajiang mini vehicle is carried out according to the following steps:
1) Check whether the main bearing is present . Look for signs of rust, ablation and scaling and observe contact. Defective bearings must be replaced. The main pad cannot be ground and repaired with sandpaper (cloth) or other processing methods.
2) Use a fine fuse or plastic wire. Gap gauges measure gaps. Cut the gap gauge to a suitable length, approximately equal to the width of the bearing, avoid the oil hole and place it on the crankshaft main shaft diameter in the axial direction, place the crankshaft on the bearing and lift; The cover ofe bearing at 43.0-48.0 N·m. Tighten with the tightening torque. Each main journal presses a gap gauge. Do not rotate the crankshaft at this time. Remove the bearing cover, remove the flattened wire gauge and use a micrometer. to measure the line at the widest (thinnest) point of the wire gauge. The gauge thickness is used to determine if the deviation is within the specified limit. The standard gap between main bearing and trim bearing is 0.022 to 0.041. mm, and the limit is 0.08 mm. If it exceeds the limit, replace the liner to close the gap. If the packing still exceeds the specified limit after replacing the packing, the shaft diameter can be ground smaller and a corresponding small-quality packing is installed. The radial gap between the small main bearing and the lining is 0.02-0.071mm.
Crankshaft Bearing Size
Sizeof bearing
Crankshaft main bearing diameter/mm
Standard
49.985-50.000
< /p>
Small shape
Grade I grinding size 0.25
49.735-49.750
< p >Grinding grade II 0.50
49,485-49,500
14. How to repair the connecting rod
Songhuajiang mini car connecting rod Carry out the inspection according to the following steps:
(1) Check the end play at the big end of the connecting rod. When the connecting rod and crankshaft rod journal are connected, measure the end play. at the large end of each connecting rod. The measurement results must meet the requirements, otherwise the connecting rod or crankshaft must be replaced.
Connecting rod big end axial play limit
Big end axial play/mm
0.36-0.59
< p> 0.7 p>
Connecting rod big end width/mm
21.71-21.84
< p>Crankshaft side connecting rod journal width/mm
22.2-22.3
(2) Correctionof the connecting rod During use, the connecting rod may bend or twist when it exceeds the use limit, it should be corrected or replaced. The parallelism deviation of the large and small axes of the connecting rod head holes must not be greater than 0.1 mm over a length of 100 mm. The bending limit of the connecting rod is 0.05 mm. Inspection of connecting rod twist is shown in Figure 2-36. bending inspection is shown in Figure 2-37. When the connecting rod is found to be bent or twisted, recall when it is bent or twisted and check whether the small end of the connecting rod is worn or otherwise damaged; measure the gap between the bushing hole at the small end and the connecting rod; piston pin. If the bushing is worn or damaged, the damage is severe, or the measured clearance exceeds the limit, replace the connecting rod.
Limit value of the clearance between the ring and the piston pin
The clearance between the ring and the pinof piston
0.0125 -0.0175
0.05
Inner diameter of small end ring
p>
16.005-16.015
Piston pin diameter
15.99-16.00