As the compressor works, the cylinder-piston group wears out, the tightness of the valves is broken

In case of these malfunctions, the filling time of the pneumatic system (until the control lamps go out) at an engine speed of 2200 rpm exceeds the specified specifications, i.e. 8 minutes, or the compressor does not develop the set pressure at all 7 ... 7, 5 kgf/cm2

In addition, the wear of the cylinder-piston group leads to the suction of oil mist from the compressor crankcase into the cylinders, and then the oil, together with air, goes to the pneumatic system.

After filling the pneumatic system with air in the pressure regulator, the unloading valve opens, the oil, together with the air, is thrown out and settles on the regulator and the frame.

It should be noted here that the oil flow through the compressor increases due to the contamination of the engine air filter.

The fact is that the compressor draws filtered air from the engine intake manifold.

As the filter becomes dirty, the vacuum in the intake manifold increases, and the compressor, even with a working piston group, sucks in oil mist from the crankcase, and then, on the exhaust stroke, throws it into the pneumatic actuator.

Leakage of the gasket 18 of the cylinder head, internal cracks in the head or block lead to the fact that the liquid from the cooling system is sucked into the cylinders, and then, together with the air, goes to the pneumatic drive.

The coolant level in the expansion tank drops, and the liquid in it boils. This is because the piston on the compression stroke pushes air into the compressor cooling jacket, and then the air and liquid merge into the expansion tank.

There is one more dangerous consequence of the considered malfunctions.

The liquid that has entered the compressor cylinder, through the gaps between the cylinder, piston and rings, seeps into the compressor crankcase, and from it flows into the engine oil pan.

In case of liquid getting into the oil, the compressor must also be taken into account when looking for a leak.

Otherwise, due to a faulty compressor, a serviceable engine may be erroneously sent for repair, and a faulty compressor is reinstalled on another serviceable engine.

Oil for lubricating the compressor is supplied from the central oil channel of the engine to the mechanical seal 4 installed in the crankshaft.

The seal is pressed against the flywheel housing by spring 5.

In case of significant wear of the mechanical seal, as well as breakage of the spring, the oil, bypassing the compressor, flows directly onto the timing gear unit and further into the engine sump.

This malfunction can cause failure not only of the compressor (jamming due to lack of lubrication), but also of the engine (rotation of the crankshaft liners due to oil starvation).

Incomplete opening of the exhaust valves leads to overheating of the air at the compressor outlet.

Compressor Disassembly

Disassembly of the compressor fixed on the stand begins with the removal of the cylinder head. Then, the intake valves, their guides and seats are removed from the sockets of the cylinder block.

Clamping the head of the block in a vise, unscrew the plugs of the discharge valves, remove the valves, seats and gaskets.

Bending the antennae of the lock washer 2, and unscrewing the nut 3 of the crankshaft drive gear, remove the lock washer.

Then, using the tool, the compressor drive gear is removed and the key 6 is removed from the groove of the crankshaft.

In order to remove the mechanical seal and spring from the crankshaft, you must first remove the thrust ring from the crankshaft.

Turning the compressor on the stand with the bottom cover up, unscrew the mounting bolts and remove the bottom cover with gasket 24.

Then you need to unpin and unscrew the nut securing the connecting rod caps, remove the caps.

By tapping with a hammer on the end of the lower head of the connecting rod, the piston with the connecting rod is taken out.

After removing the liners, it is necessary to connect the caps and connecting rods in pairs with bolts so as not to confuse them in the future. The connecting rod with the cover is machined as an assembly, so they are only replaced in pairs.

Turning the compressor with the cylinder block up, unscrew the nuts securing the block to the crankcase and remove the cylinder block with oil deflector plates 21.

After that, unscrew the bolts securing the rear crankcase cover 23 and remove the cover.

Before the crankshaft is pressed out of the crankcase, the thrust ring of the main bearing, installed on the side of the drive gear, is removed.

Having clamped the connecting rod in a vise, remove the compression oil scraper rings from the piston, remove the piston pin thrust ring.

After the piston pin 14 is pressed out, the piston is disconnected from the connecting rod, and then pressed intotulku from the upper head of the connecting rod.

Compressor Parts Detection

In case of fault detection, parts with cracks, chips, scuffs and risks on working surfaces, other mechanical damages are subject to rejection.

Size

Diameter

cylinder, mm

Marking

Nominal

60+0,03

0

1st repair

60,4+0,03

+0,4

2st repair

60,8+0,03

+0,8

When the inner surface of the cylinders is worn by more than 0.02 mm, it is necessary to bore the cylinders to the repair size (Table 1). The seat diameter for the intake valve seat must not exceed 17.027 mm.

The diameter for ball bearings in the compressor crankcase should be no more than 72.05 mm.

At a larger diameter, the bearing does not fit with an interference fit.

The non-flatness of the contact surface of the compressor head to the cylinder block should be no more than 0.1 mm.

Risks, wear marks on the surface of the discharge valve seats are eliminated by grinding and lapping the valves.

The diameter of the hole for installing the discharge valve should be no more than 28.8 mm.

Size

Diameter

connecting rod

necks, mm

Marking

Nominal

28,5-0,021

0

1st repair

28,2-0,021

-0,3

2st repair

27,9-0,021

-0,6

At the crankshaft, the diameter for ball bearings and gears must be at least 35 mm, for the mechanical seal no more than 25.05 mm, the keyway width no more than 5.02 mm.

When the connecting rod journals are worn, they must be reground to the next repair size (Table 3).

Group

Hole diameter

under the finger

in the sleeve, mm

Color

markings

I

12,507...12.504

 

White

II

12,504...12,501

 

Green

III

12,501...12.498

 

Blue

IV

12,498...12,496

Red

The non-parallelism of the axes of the holes of the upper and lower heads of the connecting rod (bending) over a length of 100 mm should be no more than 0.1 mm.

Distortion of the axes of the holes of the upper and lower heads (twisting) over a length of 100 mm should be no more than 0.15 mm.

The diameter of the lower end of the connecting rod must be no more than 32.02 mm, and the diameter of the bushing of the upper head no more than 12.507 mm.

If the top head bushing is loose, it must be replaced.

When replacing a bushing, drill a lubrication hole and turn the bushing to the nominal size.

The connecting rods are divided into groups through 0.003 mm according to the smaller diameter of the hole and are marked with paint (Table 4).

Size

Piston diameter, mm

Marking

At the skirt

At the bottom

Nominal

59,9-0,03

59,8-0,03

-

1st repair

60,3-0,03

60,2-0,095

+0,4

2st repair

60,7-0,06

60,6-0,195

+0,8

The height of the discharge valve plug must be at least 31.1 mm.

The seat diameter of the seal is at least 24.94 mm.

At the compressor drive gear, the tooth thickness along the chord of the pitch circle must be at least 4.2 mm, and along the width of the keyway not more than 5.15 mm.

Group

Hole diameter

under the finger

in the piston boss

(finger diameter)

Color

markings

I

12,500... 12,497

 

White

II

12,497.. .12,494

 

Green

III

12,494.. .12,491

 

Blue

IV

12,491... 12,488

Red

It is not allowed to wear the piston near the bottom and skirt by more than 0.015 mm from the nominal or repair size (Table 5).

The oversize pistons are marked on the outer surface of the bottom. The diameter of the hole in the piston boss under the finger is allowed no more than 12.5 mm.

According to the diameter of the hole in the boss, the pistons are divided into groups at intervals of 0.003 mm (Table 6).

Piston pin diameter must be at least 12.488 mm. The fingers are sorted into groups by diameter.

Dimensions and markings by groups correspond to the sizes and markings for pistons (see table 6).

It is not allowed to wear the liner by more than 0.01 mm from the nominal or repair size (Table 7).

Size

Толщина, мм

Маркировка

Nominal

1,75-0,013

-

1st repair

1,90-0,013

-0,3

2st repair

2,0,5-0,013

-0,6

When checking, piston rings are installed in ring gauges.

The gap in the lock of the piston ring installed in the caliber must be within 0.2 ... 0.6 mm.

Repair kits of rings are marked with green paint, diameters of gauges for checking rings are shown in table 8.

Size

Диаметр

калибра, мм

Маркировка колец

Nominal

60

Not marked

1st repair

60,4

One strip 10 mm wide

2st repair

60,8

Two strips 10 mm wide

Compressor assembly

Before assembling the compressor, you need to select:

  • - by groups, piston pins to pistons and connecting rods with bushings pressed into them;
  • - according to repair dimensions pistons to cylinders;
  • - according to the repair dimensions, piston rings to pistons;
  • - according to repair dimensions, crankshaft liners. When pressing the bushing into the upper head of the connecting rod, make sure that the hole in the bushing coincides with the oil channel in the connecting rod.

The piston pin must be matched to the holes in the piston bosses with a clearance of 0.003 mm, and enter the piston holes under the action of light hammer blows.

The clearance between the piston pin and the connecting rod bushing must be within 0.004 ... 0.010 mm. The finger should fit snugly into the hole of the sleeve from the force of the hand.

Having previously lubricated the friction surfaces with engine oil, it is necessary to install the connecting rod in the piston and, having aligned the holes, press in the piston pin. In the piston, the pin is fixed by thrust rings.

Then rings are installed on the piston.

Compression rings are installed on the piston with a stepped groove upwards, the joints of adjacent rings should be directed in opposite directions.

The gap between the ring and the groove should be 0.035...0.09 mm.

The next step is to assemble the compressor head. To do this, install the gaskets of the discharge valve seats into the head, screw in the valve seats, insert the discharge valves, springs and plug gaskets, screw the discharge valve plugs.

The crankshaft assembly with bearings is installed in the compressor crankcase until it stops against the ring.

Then, a key is installed in the groove of the crankshaft, a gear is mounted on the shaft and the key, which is fixed on the shaft with a nut with a lock washer.

The spring and seal installed in the crankshaft are fixed with a thrust ring.

After installing the seal, it is necessary to check its mobility: when you press the end with your finger, the seal should move freely.

Having installed the compressor crankcase on the stand, and having selected a set of gaskets 22, attach the rear cover to the crankcase.

Then, having installed the plate reflector 21 on the crankcase, fix the cylinder block on it.

Turning the cylinder block with the crankcase assembly on the stand with the crankcase up, blow the cylinders and crankshaft with compressed air.

Install liners of the same repair size with the crankshaft journals on the connecting rod and in the connecting rod cover.

After lubricating the surfaces of the cylinders, pistons and connecting rod journals of the crankshaft with engine oil, install the pistons with connecting rods as an assembly into the cylinders.

Then, install the covers as an assembly with liners on the crankshaft journals and tighten the fastening nuts with a torque of 1.6 ... 1.8 kgm, cotter the nuts.

Then check the ease of rotation of the crankshaft. The turning moment should not exceed 0.8 kgf m. Having previously lubricated the contact surfaces with nitro enamel, fasten the bottom cover with the gasket to the crankcase.

Having pressed the intake valve seats into the cylinder block, install the guides and valves.

After installing the intake valve springs and gasket 18, secure the head to the cylinder block. Tighten the head nuts evenly in two steps.

The final tightening torque of the nuts should be 1.2...1.6 kgm.