The vehicle accelerates poorly
There are many reasons for a deterioration in acceleration, but the main ones can be identified as follows.
- Engine fault: loss of compression in one or more cylinders, coking of the exhaust system or damage to the exhaust catalytic converter.
- Fuel system fault: clogging of the fuel injectors, fuel filter, pipes and hoses of the fuel supply system. Use of poor-quality fuel or fuel unsuitable for the season.
- Turbocharging system fault: failure of the turbocharger or a loose fit of the system hoses on the intercooler or turbocharger connections (air leak).
- Engine management system fault: failure of system sensors. If any sensor fails, the electronic control unit switches to a back-up programme that allows you to reach a garage, but engine power and fuel economy are reduced.
- Clutch slip: due to wear of the driven plate or a fault in its release mechanism.
- Brake system fault: partial dragging of one or more wheels on the move, incorrect adjustment of the parking brake.
- Insufficient tyre pressure or vehicle overloading.
First of all, check the tyre pressures and bring them up to the correct values.
Checking the operation of the brake system and the parking brake
There is no need to remove the wheels for this. Find a level stretch of road and, in dry, windless weather, carry out a coasting test of the vehicle.
The vehicle must be fully fuelled, with only the driver in the cab.
Accelerate the vehicle to 50 km/h, steady the speed, then depress the clutch (or move the lever to neutral) and coast to a complete stop.
Carry out another run in the opposite direction. A serviceable vehicle should coast for about 500 m.
Checking the operation of the clutch
The initial check is carried out on a level area free of obstructions. Using the accelerator pedal, set an increased idle speed — approximately 1500 rpm.
Hold the vehicle with the parking brake. Depress the clutch and engage first gear.
Then begin to release the clutch pedal smoothly. If the engine stalls, the clutch is serviceable and does not slip.
If the engine does not stall, the clutch is worn and requires replacement. Note: no manual adjustment of the clutch is provided in service; wear is automatically compensated for by a special device in the slave cylinder of the hydraulic drive.
The engine stalled while driving
- First of all, find out whether there is fuel in the tank. Switch on the ignition and look at the fuel level gauge. If the reserve warning lamp is not lit and the needle shows fuel present, it can be assumed that there is fuel in the tank.
- Open the bonnet and carefully inspect the engine compartment. Pay attention to the integrity of all assemblies.
- Check that all wires are in place and that none are broken, burnt or have damaged insulation.
- Inspect the supply line: it may be pinched or blocked, in particular by paraffin (wax) deposits — usually due to poor-quality diesel fuel or its grade not matching the season of use. In this case, after the vehicle has stood for several hours in a warm room (at an air temperature of no less than +10 °C), the engine starts without problems.
- Paraffin deposits usually accumulate in the fine fuel filter or in the strainer of the fuel pick-up module installed in the fuel tank. Clogged filters can also cause the fuel injectors to clog.
- Check the injection system fuse fitted in the fuse box (see the article – Replacing fuses and relays). Replace a blown fuse.
- Inspect the expansion tank of the cooling system: check whether coolant has leaked out.
- Also check the oil level in the engine sump.
- If everything is in order, proceed with the check of the engine management and fuel systems described earlier.
- In addition, a sudden engine stop and the impossibility of a subsequent start may be caused by failure of the crankshaft position sensor or by disconnection of its wiring harness connector.
Loss of oil pressure
The instrument cluster of the GAZelle Next has a warning lamp for critical loss of engine oil pressure. For reliable engine operation, a sufficiently high pressure must be maintained in the lubrication system at all times.
Open the bonnet. Do not rush to check the oil level straight away: let the oil drain into the sump — this takes two or three minutes.
During this time, carefully inspect the engine for fresh oil streaks. Look under the front of the vehicle: check whether the engine sump is holed or leaking.
Pay attention to the oil filter. Oil may seep from under the rubber gasket if it is damaged, or from under the filter itself if it is not tight enough. Sometimes it is enough to tighten it slightly clockwise.
Wipe the dipstick with a clean rag and reinsert it fully.
Remove the dipstick again. If the oil level is close to the lower mark or below it, top up the oil to the correct level.
Start the engine. If the warning lamp goes out at a normal level, you may continue driving.
If the lamp remains lit, check the serviceability of the oil pressure sensor. To do this, unscrew the standard sensor and fit a mechanical pressure gauge in its place.
If the pressure at minimum idle speed is more than 25 kPa (0.25 kgf/cm²) and rises with engine speed, the sensor or its electrical circuit is faulty.
If you do not have a pressure gauge, all you can do is check the reliability of the contact in the sensor wiring connector or replace the sensor with a known good one.
If, after all visible causes have been eliminated, the engine oil pressure remains insufficient (the warning lamp is lit), carry out diagnostics and repair of the engine.
Engine overheating
The vehicle's instrument cluster includes a coolant temperature gauge. If the engine overheats, the needle approaches the red zone. At the same time, the engine overheating warning lamp comes on.
At the first signs of overheating, if the needle has moved into the red zone but no clouds of steam are coming from under the bonnet, turn the temperature control for the air entering the cab to the extreme right (hottest) position and switch the heater blower to maximum speed.
Let the engine run for a couple of minutes at normal idle speed with the heater at full power.
Important: do not stop the engine immediately! The only condition is that the cooling system remains sealed. If a hose has burst or slipped off, or another leak has developed (other than coolant escaping from under the expansion tank cap), the engine must be stopped immediately!
After an overheated engine is stopped, localised overheating of the coolant begins where it contacts the most heat-stressed components, and vapour locks form. This phenomenon is called heat shock.
- Stop the engine.
- Open the bonnet and inspect the engine compartment. Determine where the steam is coming from.
When inspecting the engine, pay attention to the presence of coolant in the expansion tank and to the integrity of the rubber hoses, radiator and thermostat.
Warning: never open the expansion tank cap immediately on a hot engine! The coolant in the cooling system is under pressure. When the cap is opened, the pressure will drop sharply, the fluid will boil and its splashes can cause serious scalds. If the cap must be opened, first cover it with a thick rag and only then turn it very carefully.
Look under the instrument panel: check for coolant leaks from the radiator or heater hoses.
If leaks are found, a burst hose can be temporarily repaired with adhesive tape. Reinforced (for example, silver-coloured) adhesive tape is particularly suitable for this purpose.
A leak from the radiator, thermostat or heater is quite difficult to fix on the spot, so in such a situation you need to top up the cooling system with water and, while driving, watch the temperature gauge carefully, periodically restoring the level.
Important: prolonged use of water instead of antifreeze leads to scale formation in the cooling system, poorer heat transfer and a shorter engine life. Never add cold water to an overheated engine. The engine must cool with the bonnet open for at least 30 minutes.
If there is no coolant leak, check the condition and tension of the auxiliary drive belt (see the article – Replacing the auxiliary drive belt). Replace a broken belt or adjust its tension.
The engine may also overheat if the thermostat fails; the thermostat regulates the flow of fluid through the radiator or bypassing it (to speed up warm-up of a cold engine).
If the lower radiator hose is cold while the engine is overheating, the thermostat is faulty and there is no circulation through the radiator.
A common cause of engine overheating is failure of the viscous coupling through which the fan impeller is driven. Start the engine, watch the temperature and note whether the cooling fan starts to rotate when overheating occurs. If it does not rotate, replace the coupling.
Two valves are fitted in the expansion tank cap: an inlet valve and an outlet valve. The outlet valve maintains an excess pressure in the system of at least 0.10 MPa (1.1 kgf/cm²), raising the boiling point of the coolant. If the valve jams in the closed position, overheating produces a considerable excess pressure (over 0.15 MPa), which can rupture the tank or blow off the hoses. Jamming in the open position leads to premature boiling of the fluid.
The battery is not charging
If the red battery discharge warning lamp is lit on the instrument cluster, it means that current is not flowing from the alternator into the vehicle's electrical system and the battery's energy reserve is being used up.
Operating the vehicle with the lamp lit is not permissible, as sometimes the cause may be a short circuit in the wiring, leading to a fire in the engine compartment.
Stop the vehicle, switch off the engine and determine the cause.
If the cause was not a short circuit and the battery was fully charged, you can reach the garage even without the alternator, but it is better to try to eliminate the fault on the spot.
Check whether the auxiliary drive belt is broken. If the belt is intact, check its tension. If the deflection is not within specification, check the operation of the tensioner and, if it is serviceable, replace the belt.
If the lamp remains lit even after the belt has been tensioned, check whether the 90 A cartridge fuse in the fuse box located in the engine compartment on the common bracket with the engine control unit has blown. If the fuse has blown, replace it and start the engine.
If the voltage reading on the display does not flash (the voltmeter needle is in the green zone of the scale and the warning lamp has gone out), the voltage is within specification and you may continue driving.
The wires may be broken, snapped inside the insulation or have oxidised contacts. Eliminate the fault and start the engine. If charging current appears, you may continue driving.
If the lamp has not gone out even after these measures, the possible cause lies in the alternator itself. Such faults are best rectified at a garage. To reduce current consumption when driving with a faulty alternator, switch off the radio, unnecessary lighting, the heater blower, etc.
Extraneous knocking has appeared
- 1. Main bearing knock (heard at the very bottom of the cylinder block) — very dangerous; stop the engine immediately, the vehicle will have to be towed to the garage.
Character: low-pitched knock, noticeably intensifying under load and as crankshaft speed increases. Often accompanied by a drop in oil pressure (the lamp is lit almost constantly). - 2. Big-end bearing knock (heard in the middle of the cylinder block) — very dangerous; stop the engine immediately.
Character: rhythmic, ringing, metallic sound of medium pitch. It increases significantly with load and disappears completely when the fuel injector is cut out. - 3. Gudgeon pin knock (heard at the top of the cylinder block) — dangerous; without loading the engine, you can drive to the garage under your own power.
Character: rhythmic knock of high pitch with a sharp metallic tinge, audible in all modes and intensifying with load. It disappears completely when the fuel injector is cut out.
Knock of worn pistons and cylinders (heard in the same area) — not dangerous. A sound reminiscent of earthenware knocking together. Particularly audible on a cold engine, it diminishes or disappears as the engine warms up. - 4. Valve knock (heard at the top of the engine near the cylinder head cover) — not dangerous, you can drive to the garage under your own power.
Character: metallic knock against a background of general muffled noise. Clearly audible at low and medium engine speeds from the cylinder head side, above the valve locations.
Knocking in the suspension
If extraneous knocks appear in the suspension of a moving vehicle, their source must be identified immediately. The condition of the suspension is best checked with the vehicle on a ramp, an inspection pit or a lift. In any case, you will need an assistant.
Causes of suspension knocks and remedies
- Cause: faulty shock absorbers.
Remedy: replace the shock absorbers. - Cause: loose anti-roll bar link mounting bolts; worn cushions and rubber-metal bushes of the links.
Remedy: tighten the link mountings; replace the rubber cushions if worn. - Cause: damage or deformation of the cushions of the upper mountings and the bushes of the lower mountings of the shock absorbers.
Remedy: replace cushions and bushes with torn, cracked or extruded rubber. - Cause: wear of the ball joints and supports of the front suspension.
Remedy: replace the ball joints and supports. - Cause: excessive clearance in the front wheel hub bearings.
Remedy: replace the bearings. - Cause: severe wheel imbalance or deformation of the wheel rim.
Remedy: balance the wheels or replace the rim. - Cause: sagging or breakage of the front suspension spring.
Remedy: replace the spring. - Cause: wear of the rubber bushes in the eyes of the rear suspension leaf springs and in the frame brackets.
Remedy: replace torn or cracked bushes. - Cause: knock from the suspension «bottoming out» due to destruction of the compression buffers.
Remedy: replace the damaged buffers. - Cause: loosening of the U-bolt nuts securing the rear leaf springs or frequent «bottoming out» due to overloading.
Remedy: tighten the nuts and avoid overloading.
Knocking and vibration in the propeller shaft
- Cause: knock on sudden changes in driving mode and during gear changes (loosening of the nuts securing the propeller shaft to the final drive flange or the intermediate support).
Remedy: tighten the nuts. - Cause: wear of the bearings and trunnions of the universal joint crosses.
Remedy: replace the crosses. - Cause: vibration (lost balance plate, incorrectly assembled splined joint, excessive runout of the sliding yoke, worn joints, broken drive pinion flange, bent shaft tube).
Remedy: balance the shaft, fit the parts according to the marks, replace defective parts (after replacing the splined yoke, the shaft must be rebalanced without fail). - Cause: increased noise (destroyed cage of the intermediate support bearing).
Remedy: replace the support as an assembly.
Knocking in the rear axle
- Cause: loud axle noise (hum) (loosened nut securing the drive pinion flange, worn or damaged bearings).
Remedy: tighten the nut, check the condition of the bearings and replace them if necessary. - Cause: pulsating axle noise (loosened crown wheel mounting bolts or crown wheel fitted askew).
Remedy: tighten the crown wheel mounting bolts and check its runout. - Cause: high-pitched noise (whine) (insufficient oil level, oil that is too thin, incorrectly adjusted tooth contact between the gears, scoring on the working surfaces).
Remedy: restore the oil level, replace the oil with the recommended grade, check the contact pattern and adjust it, replace the gears. - Cause: heavy knocking in the axle on sudden acceleration after coasting or in corners (severe wear of differential parts).
Remedy: check the total backlash in the final drive and differential. Replace worn parts. - Cause: continuous knocking and crunching in the axle (worn teeth or bearings).
Remedy: replace worn parts.
Vibration and shocks at the steering wheel
The cause of knocking from below may be faults not only in the suspension but also in the vehicle's steering.
- Cause: increased clearance in the front wheel hub bearings.
Remedy: replace the bearings. - Cause: loosened nuts securing the track rod ball pins or increased clearance in the ball joints.
Remedy: tighten the nuts or replace the track rod ends. - Cause: loosened steering gear mounting.
Remedy: tighten the steering gear mounting.
A possible cause of vibration and shocks at the steering wheel when driving above 70–80 km/h may be front wheel imbalance.
If shocks and vibration at the steering wheel appear when the brake pedal is pressed, the brake pads must be replaced and the front brake discs repaired or replaced.
Brake problems
Reduced braking efficiency, skidding under braking and brake pedal pulsation should be a signal for an urgent brake check.
Regularly check the brake fluid level (DOT 4 is recommended) in the master cylinder reservoir. The level must be between the MAX and MIN marks on the reservoir wall.
A cause of lost braking efficiency may be unsatisfactory operation of the vacuum brake servo. For a quick check, press the brake pedal several times with the engine off to release the vacuum, then, holding the pedal down, start the engine. If the pedal sinks slightly after the engine starts, the vacuum servo is serviceable.
If the pedal remained motionless, check the integrity and security of the hose attachment to the non-return valve of the vacuum servo and to the engine vacuum pump.
Replace or repair the faulty hose. If the hose is serviceable, the vacuum servo must be replaced.
If braking is accompanied by judder and pulsation of the brake pedal, the condition of the front disc brake mechanisms should be checked first.
With the vehicle on a jack, remove the front wheel and check the mobility of the brake pads. To do this, through the window in the calliper, try to lever the pads away from the brake disc with a screwdriver. If the pads cannot be spread apart, they have lost mobility in the calliper seats or the piston has seized in the brake cylinder.
Seizure of the piston leads to constant dragging of the wheel, loss of directional stability and skidding. Having unscrewed the upper calliper mounting bolt, swing the calliper up and check the mobility of the pads. If they move with difficulty, clean the end faces of the pad backplates and the seats in the guide from dirt and rust.
At the same time, check the thickness of the pad linings. If it is less than 2 mm, replace the pads. Inspect the brake disc: its thickness must be at least 30 mm, and the surface flat and smooth on both sides. If the surface is covered with rust, try to clean it with fine-grit abrasive paper. If this does not help, the discs must be machined (skimmed) or replaced.
If braking is accompanied by jerking of the vehicle and squealing near the rear wheels, with the rear end skidding, check the condition of the rear wheel drum brake mechanisms.
With the vehicle on a jack, remove the rear wheels and brake drums one at a time. Measure the diameters of their working surfaces.
The inner diameter of the drum must not exceed 283.0 mm; the working surface must be even and smooth, without circumferential scoring and clearly visible ovality (runout of no more than 0.5 mm).
If the inner diameter of the drum exceeds the permissible value, the circumferential scoring is very deep or uneven wear is clearly visible, the drum will have to be replaced with a new one.
