Compressor (Fig. 1) piston type, indirect, two-cylinder, single-stage compression

Air from the engine air filter enters the compressor cylinders through the reed inlet valves.

The air compressed by the pistons is displaced into the pneumatic system through reed discharge valves located in the cylinder head.

The block and head are cooled by liquid supplied from the engine cooling system.

The compressor cooling system only fills when the engine is running.

Ural car compressor

Oil to the rubbing surfaces of the compressor is supplied through a tube from the engine oil line to the rear cover of the compressor crankcase and through the seal through the channels of the crankshaft to the connecting rod bearings.

Signs of a malfunctioning compressor are noise during its operation, knocking, increased oil content in the condensate drained from the air cylinders.

Increased oil content in the condensate is usually the result of wear on the piston rings and the bearings of the lower heads of the connecting rods.

The compressor is installed in the rear part of the engine camber (Fig. 2) and is fixed with four bolts 15 to the front wall of the cover 14 of the timing gears, made in the same casting as the flywheel housing.

Installing a compressor on a Ural car engine

Compressor maintenance

Fit valves that do not provide tightness, lap them into the seats, worn or damaged - replace.

Lap new valves onto their seats until continuous ring contact is obtained when checking for paint.

Tighten the block head stud nuts in pairs, starting with the middle diametrically located pair.

Tighten the nuts in two steps: the final tightening torque should be 12-16 N.m (1.2-1.6 kgf / m).

Ural car compressor

Signs of a compressor malfunction: the appearance of noise and knocking, increased heat, increased oil content in the condensate, which is usually the result of worn piston rings and sealing of the rear end of the crankshaft, connecting rod bearings or clogging of the oil drain pipe from the compressor.

To remove the compressor from the engine, drain 10 liters of coolant from the cooling system through the tap on the heater boiler.

Loosen the hose clamp and disconnect the ejection pipe from the damper.

Remove air filter cover 2, filter element 4 and air filter housing 6.

Unscrew the fuel line bolts and union nuts, disconnect the fuel lines from the solenoid valve 7 and the spark plugs of the electric torch starter.

Disconnect the wires from the solenoid valve and spark plugs.

Remove the bolts and remove the connecting pipe 1 of the intake manifolds together with the solenoid valve.

Ural car compressor head

Close the openings on the air ducts with cardboard or plywood plugs.

Unscrew the two nuts 13 securing the flange of the coolant supply pipe to the compressor, then the union nut 11 and remove the pipe 12.

Remove the tube flange and the rubber o-ring.

Unscrew the union nuts and disconnect from the compressor the pipelines connecting the compressor with the car's pneumatic system and the radiator of the engine cooling system.

Remove the four bolts 15 securing the compressor to the cover 14 of the timing gears.

Remove the coupling from pipe 38 (Fig. 3) and take the compressor forward to the fuel pump until gear 10 comes out of the cover, remove the compressor.

Close the hole in the lid with a plywood or cardboard plug.

Compressor disassembly

Unbend the tab of the lock washer 5, unscrew the nut 6 and use the puller "I 801.02.000" to remove the gear 10 from the shaft 4.

Unscrew the plugs 3 (Fig. 4►) of the discharge valves, remove the springs 5 ​​and valves 4.

Compressor diagram

Unscrew saddles 6 using a 10 x 10 square wrench.

The valve plates and seats are ground to each other, so they should not be depersonalized during repairs.

Unscrew bolts 39 (see Fig. 3), remove pipe 38.

Unscrew the nuts 21, protecting the gasket 23 from damage, separate the head 19 from the block 24, remove it and the gasket.

Remove spring 35 and intake valve 36.

If necessary, use a puller (fig. 5) to press 37 inlet valve guides (see fig. 3).

Remove bolts 33 and carefully, protecting gasket 2 from damage, remove cover 1 and gasket.

Compressor inlet valve seat puller

Mark the connecting rods and connecting rod caps and their relative positions.

Unpin and unscrew the nuts of the connecting rod bolts, remove the connecting rod caps and remove the pistons 18 as an assembly with the connecting rods.

Install the connecting rod caps on the connecting rods in their original position and fasten with connecting rod bolts.

Fix the connecting rod assembly with the piston in a vice, remove the rings from the piston: two compression 17 and one oil scraper 15.

Remove the retaining rings 22 of the piston pin, remove it and disconnect the connecting rod from the piston.

Unscrew the nuts 26 of the studs securing the cylinder block 24 to the crankcase 12.

Remove block 24, deflector plate 28 and gasket 27 from the studs.

Remove retaining ring 9, seal 7 and seal spring 8 from the rear end of the crankshaft.

Unscrew bolts 30 and remove cover 31, gasket 29.

Remove retaining ring 3 from the rear end of crankcase 12, place the crankcase with its front end on a press and press shaft 4 complete with bearings 11 and 32 out of the crankcase through a spacer made of “soft” non-ferrous metal.

Press the shaft out of the bearings. If necessary, unscrew the studs from the compressor crankcase.

When repairing the connecting rod and piston group, worn pistons, piston rings and liners must be replaced with repair kits.

The cylinders of the block and the crankshaft are repaired: the cylinders are bored and honed, the connecting rod journals of the crankshaft are ground to the repair dimensions (Table 1).


Size, mm






Compressor crankcase

Hole Diameter

for crankshaft bearings





Cylinder block.

Cylinder diameter





Crankshaft.Journal diameter:

Main bearings

Crankset for bushings

Under drive gear













Connecting rod assembly with cap

Pin Pin Hole Diameter




Wall thickness




Piston.Outer diameter:









Compression ring

Joint clearance when set in gauge

Gauge diameter







Oil scraper ring

Joint clearance when set in gauge

Gauge diameter







When assembling newly installed parts of the piston group, pistons, connecting rods and pins should be selected in groups (Table 2).


Thinger Ø

Ø Piston holes

Ø Holes in

Connecting Rod Bushing

Ø Color




12,500—1 2,497











12.50 1-12.498







Details of the first and second repair sizes are marked:

The numbers + 0.4 and + 0.8 are stamped on the bottom of the pistons, the numbers - 0.3 and - 0.6 are stamped on the liners on the back (steel) side, the rings on the generatrix are applied with green paint one or two stripes wide 10 mm.

Drift for installing pistons in compressor cylinders

Before assembling the cylinder block and compressor head, check for tightness with compressed air at a pressure of 15 kgf / cm2 with immersion in water, the absence of nicks and warping of the parting planes.

The warping of the parting planes (0.040 mm) is controlled by a curved ruler and a feeler gauge.

A probe with a thickness of 0.05 mm should not pass under the ruler installed on the connector plane.

Check the connecting rod for bending and twisting on a special tool. Non-parallelism of the axes of the upper to the lower (the connecting rod heads are allowed 0.070 mm over a length of 100 mm, their twisting is 0.100 mm over a length of 100 mm.

Assemble the compressor in reverse order of disassembly. In this case, it is necessary to fulfill a number of the following mandatory requirements:

  • - generously lubricate the parts of the connecting rod and piston group with oil used for engine lubrication according to the lubrication map;
  • - install the compression rings on the piston with the groove upwards (towards the piston bottom).
  • - before installing the pistons in the cylinder, open the joints of the rings at an angle of 120˚. Install the pistons in the cylinder using a mandrel (Fig. 6);
  • - the tightening torque of the nuts of the connecting rod bolts should be 1.5 - 4.7 kgf / m. It is not allowed to loosen the nut to install the cotter pin;
  • - tighten the head of the compressor block in two steps, the final tightening torque is 1.2 - 1.7 kgcm;
  • - when installing the seal, insert the ends of the spring into the holes on the crankshaft and the seal.

Install the repaired compressor on the car in the reverse order of removal.

We also look at the article about the compressor - "Repair of the compressor of the Kamaz car"