A compressor is installed on GAZ-66 vehicles (Fig. 1), designed to inflate tires with air

Vehicle compressors with a tire pressure control system (GAZ-66-01, GAZ-66-02, GAZ-66-04, GAZ-66-05) differ from car compressors without this system (GAZ-66 and GAZ- 66-03) by the fact that an unloading cylinder is screwed into the threaded hole of the compressor head above the inlet valve instead of a plug (Fig. 2).

GAZ-66 car compressor

The piston type, single cylinder, air-cooled compressor is driven through a pulley together with the power steering pump by two belts from the engine crankshaft pulley.

A compressor clutch is installed on the splines of the compressor crankshaft.

The clutch is moved by a fork mounted on a roller, the position of which is fixed with a ball lock.

GAZ-66 compressor head

The compressor receives air from the engine air filter, the compressor receives lubricant from the car engine.

Compressor maintenance

Check the tension of the compressor belts periodically. The belts are tensioned by tilting the power steering pump.

The angle of inclination of the pump should ensure that oil is filled up to the “oil level” mark on the pump reservoir, and if there is no mark, up to the reservoir filler filter.

If the slope does not provide tension to the belts, then rearrange the pump.

If the belts are too tight, rearrange the pump brackets to additional holes in them.

The tension is considered normal if, when you press your finger on the belts between the pump pulleys and the engine crankshaft, the belts bend by 15-20 mm.

Compressor malfunctions and solutions

- Causes of malfunction


Degraded performance:

- Air leakage through valves or piston rings

Repair compressor

- Clogged compressor air filter (for vehicles without tire pressure control system)

Wash the filter pad

- Weak drive belt tension

Adjust belt tension

Compressor overheating:

- Poor oil supply

Clean the oil lines and channels in the crankcase cover and compressor crankshaft

- Carbon deposits on the piston and piston rings

Clean parts from carbon deposits

Oil blowout with forced air:

  • - Wear of piston knees or cylinder
  • - Violation of the seal of the oil supply to the compressor

Repair compressor

Replace the seal 14 (see fig. 1) or the back cover of the compressor

- Broken seal spring

Replace spring

- Clogged oil outlet pipe

clear the pipe

Increased compressor knock:

- Wear of pistons, pins or bearings

Repair compressor

Compressor repair

Remove and disassemble the compressor in the following order.

  • - disconnect the oil outlet and inlet pipes, the inlet hose and the air outlet pipe. Remove the compressor from the engine, then disassemble it
  • - remove the pulley 10 (Fig. 1) of the compressor with bearings as an assembly;
  • - unscrew the locking screw of the compressor fork, remove the roller 7 and the fork 8 for turning on the compressor;
  • - remove clutch 9 to turn on the compressor;
  • - remove the compressor head and bracket 12;
  • - remove the connecting rod cover and take out the piston З with connecting rod 2 as an assembly from cylinder 4;
  • - remove the front and rear covers, remove the seal 14 and the spring 13 from the crankshaft seat;
  • - remove compressor cylinder;
  • - press the crankshaft bearings and remove the crankshaft 1;
  • - unscrew plug 8 (see Fig. 2) of the discharge valve, remove spring 9 and valve 10;
  • - unscrew saddle 11;
  • - unscrew valve body 14 and remove spring 13, valve 12 and valve seat 15;
  • - unscrew plug 6 (see Fig. 1) or unloading cylinder; remove the piston pin and disconnect the piston from the connecting rod;
  • - remove piston rings.

Checking the technical condition and repairing compressor parts

After disassembling the compressor to eliminate any malfunction, check the technical condition of its main parts.

If the wear of the cylinder exceeds the allowable or its mirror is damaged, repair the cylinder to one of the repair dimensions indicated in Table. 2.

Respectively oversized pistons and piston rings are available in these sizes.

The piston repair size group is indicated by numbers on the piston bottom: "+ 0.4", "+ 0.8".

Oversize piston rings are marked:

- one stripe 10 mm wide corresponds to an increase in the diameter of the ring by 0.4 mm compared to the nominal one, and two stripes - by 0.8 mm.

When repairing the crankshaft, use liners of repair dimensions, the thickness of which is increased by 0.15 and 0.3 mm.

The repair size group of the liner is indicated by numbers on its outer side: "-0.3" and "-0.6" (these liners have a thickness of 1.9-0.013 and 2,05-0,013 mm).

If nicks or annular grooves are found on the reed valves of the cylinder head, replace them and lap the new valves onto the seats to obtain continuous ring contact.

Piston pins, pistons and connecting rods are divided into four groups, which are sorted according to the diameters of the mating surfaces through 0.003 mm (Table 3).

Marking places:

  • -piston - on the boss under the finger;
  • - piston pin - on the pin plug;
  • - connecting rod - on the head under the piston pin.

When assembling, it is allowed to install the pin and connecting rod of the adjacent group.

The pins to the connecting rod and piston are selected without lubrication at a temperature of 10-30°C. The correct selection of the piston pin to the connecting rod bush is checked by touch.

When pressed with the thumb, the piston pin without lubrication should move with some resistance in the bushing of the upper head of the connecting rod.

Compressor assembly

When assembling the piston with the pin-rod assembly, lubricate the pin with clean engine oil.

When installing new rings, check the lock gap after installation in the cylinder.

The gap should be 0.20-0.40 mm, and the ring should fit snugly against the cylinder around the entire circumference (check for clearance).

Check whether the height of the ring and the piston groove match, the gap between the groove wall and the ring should be within 0.035-0.080 mm.

If the gap is smaller and the ring does not roll over the entire piston groove, the end of the ring can be lightly ground off on the finest sandpaper.

Install the compression rings in the grooves of the piston with the undercuts up, and open their joints by 180°.

In the process of assembling the compressor, check the ease of rotation of the crankshaft.

The torque required to turn it should not exceed; 0.2 kgm - before installing the connecting rod and piston group and 0.3 kgm - after installing this group and tightening the connecting rod bolts (but before installing the head).

When installing the inlet valve seat, make sure that the narrower seat band faces the valve.

Through the top opening of the head, check the valve stroke, which should be within 0.7-1.5 mm, and the discharge valve within 1.5-3.2 mm.

Testing the compressor after repair. Testing should include running-in (no load), performance testing, leak testing, and checking the operation of the unloading system.

The compressor is run in for 20 minutes at 1200 - 1350 rpm of the crankshaft.

The pressure of the oil entering the compressor must be 1.5-3.0 kg/cm2, the temperature is not lower than +40˚С.

The pressure of air cooling the compressor must ensure that the temperature of the compressor head does not exceed 90˚.

Performance test is carried out at 1200 - 1350 rpm of the crankshaft and with air injected into a 23 l tank.

When the pressure in the tank is 6.5 kg/cm2 the cavity of the tank communicates with the atmosphere through a calibrated hole with a diameter of 1.0 and a length of 3 mm; under these conditions, the compressor must maintain a pressure in the tank of at least 6 kg / cm2 when running continuously for 3 minutes.

In the specified operating mode of the compressor, the ejection of oil with forced air should not exceed 1 cm3 in 5 minutes.

Tightnessis checked on a non-working compressor by supplying air at a pressure of 5 - 5.5 kg / cm2 to the discharge pipe of the compressor head from a 1 liter tank.

The pressure drop in the cylinder should be no more than 0.3 kg/cm2 for 1 minute.

The operation of the unloading system (for compressors with unloading cylinder) is checked by supplying compressed air at a pressure of 5-5.5 kg/cm2 into the unloading cylinder.

The piston of the unloading cylinder should then descend and fully open the inlet valve.

At the same time, the tightness of the piston seal of the unloading cylinder is checked.

The pressure drop in a 1 liter tank and at a pressure of 5 - 5.5 kg/cm2 must not exceed 0.25 kg/cm2 for 1 minute .

When the pressure is released, the piston under the influence of the return spring should clearly return to its original position.

Tab. 2 Nominal and repair dimensions of the compressor cylinder and piston, mm

Size name

Deviation from










1st repair




2nd repair




Tab. 3 Dimensions and marking of pistons, pins and connecting rods by groups





Mating parts diameter


Piston pin

connecting rod





















Marking places: piston - on the boss under the finger; piston pin - on the pin plug; connecting rod - on the head under the piston pin.