The shock absorbers are faulty
Since wheel suspensions consist of a large number of parts, there may be a significant number of reasons causing noise and knocking. To make it easier to understand this multitude, we will highlight the most well-known ones.
When you hit a bumpy road, you start to feel an unpleasant sensation as if the bottom of the car is about to break through and the rubber bumpers installed on the rear axle beam will penetrate into the car. Such associations arise when the shock absorbers fail to work. Their main task is to dampen vibrations, but they can only perform their functions under normal operating conditions. No shock absorber can withstand fast driving on a broken road. Shock absorbers are especially hard hit when driving on a bad road is also accompanied by heat. Shock absorbers are hydraulic, and the MGP-10 fluid in them, compressed by a piston (without taking into account the high ambient temperature), heats up almost to boiling. When overheated, the shock absorber fluid partially loses its qualities, and the efficiency of vibration damping decreases.
Often, due to faulty shock absorbers, "breakdowns" of the car suspension occur. In this case, the load-bearing parts of the body (side members, mudguards, pillars) deform. If you do not pay attention to all this, over time you can find cracks in the body pillars. In addition, with faulty shock absorbers, the car wheels lose the necessary contact with the road, which affects traffic safety. Shock absorbers also have a hard time in winter. It takes at least half an hour of driving for the fluid to start functioning normally. Therefore, in the first half hour of driving, try to be especially gentle on the shock absorbers.
To determine the operability of the shock absorbers, you must first check for fluid leaks. A leaking shock absorber is not worth further testing. So it is clear that it must be repaired or replaced. If no leak is detected, further testing is carried out on an inspection ditch or overpass. Disconnect the lower end of the shock absorber and stretch it, then compress it. A faulty shock absorber will stretch in steps, with dips and will not resist as much in certain sections of the stroke. Moreover, when stretching, it is necessary to apply five times more force than when compressing.
To remove the shock absorber, you only need pliers and a 14 mm wrench. With the hood open, find the upper end of the shock absorber and, holding it from turning with pliers, unscrew the nut. While in the inspection ditch, unscrew the nuts of the lower shock absorber bracket mounting bolts, remove the pin and pull the shock absorber out through the hole in the lower suspension arm.
Shock absorbers of domestic and foreign manufacture are installed on VAZ cars (Poland, SFRY, Japan). Not all shock absorbers installed on VAZ cars can be disassembled and repaired. There are also non-disassemblable designs (Japan). Only some car enthusiasts dare to repair shock absorbers that can be disassembled on their own. But since such craftsmen exist, we will remind you of the order of disassembling shock absorbers, the causes of malfunctions and ways to eliminate them.
Before disassembling, the shock absorber is cleaned of dirt, washed and wiped dry. For disassembling, you will need: a vice with jaws that would not crush the body or the shock absorber eye and special keys that must be made independently (we hope that whoever took on the disassembly will also successfully solve the problem of the keys). Having secured the shock absorber in a vice, pull the rod out to the stop and unscrew the nut 18 (Fig. 59) of the reservoir. Remove the cylinder 16 with the rod 1 and its parts from the reservoir. Having released the reservoir from the vice, drain the shock absorber fluid into the vessel. To remove the compression valve from the cylinder, secure the valve body 11 in a vice and slightly rock the cylinder.
To disassemble the recoil valve, the rod 1 is clamped in a vice and the nut 12 of the recoil valve is unscrewed. The piston 6 with the valves, the guide bushing 4 of the rod, the seal 3 of the rod, the collar 2 of the seal, etc. are removed. Having disassembled the shock absorber, the parts are inspected, defective, those that have failed are replaced with new ones, washed in kerosene and assembled.
There are certain requirements for some parts:
- the valve discs and the bypass valve plate must not be deformed, and the bypass holes 10 must be free of contamination. The plate non-flatness is allowed to be no more than 0.05 mm;
- the working surfaces of the piston, piston ring 13, guide bushing 4 of the rod, cylinder 16 must not have any scoring that could impair the operation of the shock absorber;
- valve springs must be intact;
- oil seals should be replaced during any repair.
The assembly is carried out in the reverse order, taking into account the following nuances: the return valve nut is tightened to a torque of 9.8-13.7 N·m, and the reservoir nut - to a torque of 68.6-88.2 N·m.
The compression valve assembly is assembled as follows: two 0.15 mm thick disks are installed in the valve body 11, then the throttle disk 5, the valve plate 9 with the protrusion down, the spring 8 and the nut 7. The assembled valve is inserted into the cylinder. A correctly assembled unit should have a free travel of the plate of at least 1 mm. When assembling the rod unit, it is important to prevent damage to the plate 14 of the bypass valve on the end of the limiting plate 15, so as not to reduce the resistance of the shock absorber during the rebound stroke.
After getting acquainted with the shock absorber device, it will be much easier to understand the cause of a particular defect, and therefore, have a good idea of what needs to be done.
Here are the main reasons for shock absorber leaks:
- wear or damage to the seal 3 of the rod. It is replaced;
- mechanical particles getting on the sealing edges of the gland. In this case, the shock absorber fluid must be filtered;
- shrinkage or damage to the piston sealing ring 13. It is replaced;
- nicks, scratches on the rod 1, complete wear of the protective coating. Such a rod is changed, and with it the seal and liquid. The shock absorbers are filled with MGP-10 liquid in the following quantity; in the front 105-115 cm³, and in the rear 175-185 cm³. It should be remembered that the shock absorbers normally accept only the liquid recommended by the manufacturer. Only in extreme cases can the MGP-10 liquid be replaced with the AZh-12T or AZh-16A liquid;
- loosening of the tightening of the nut 18 of the tank. The nut is tightened.
If the shock absorber resists weakly when checked, the cause should be sought in: leaky rebound valve or bypass valve; breakage or sticking of ring 13 in the piston groove; insufficient amount of liquid; scuffs on the piston or cylinder; contamination of the liquid.
[The article is taken from an online resource: www.VazBook.ru]
When the shock absorber starts to knock and this knock is not caused by wear of the rubber bushings in the lugs and poor tightening of the shock absorber mounting nuts, then the "culprits" are a deformed casing 17, a loose nut 18 of the reservoir, a deformed rod 1 or cylinder 16.
Worn rubber parts and hinges
The rubber bushings of the shock absorber lugs are removed without difficulty. To replace the silent block, i.e. the rubber-metal hinge, a special device is required, manufactured by the Odessa Radial Drilling Machine Plant and available for sale.
It is more difficult to replace or repair the ball joints of the upper and lower arms of the front suspension. In the first and second cases, they must be removed. The upper ball joint is not lubricated during operation. This is ensured by using Teflon fabric impregnated with thermosetting resin as a bearing.
Considering that the ball joint and hinge housings are non-separable, their condition can only be assessed by determining the presence of play between the ball and the bearing surface. However, one should not rush to conclusions. The tactics for detecting the true source of extraneous knocking can be as follows:
- by grasping the upper edge of the front wheel with both hands and rocking it, determine if there is any noticeable play;
- place the car on stands. It is desirable that they be 280-300 mm high;
- adjust the clearance in the hub bearing of the wheel being examined, thus eliminating one unknown;
- at the moment when the assistant is rocking the suspended wheel, determine the presence of play by alternately touching the hinge or silent block with your hand.
It is important to remember that the permissible gap between the ball and the upper support bearing should not exceed 0.8 mm.
To determine the further operability of the ball joint, it is necessary to support the hub on one of the supports (280-300 mm high), clean the area where the conical plug is located from dirt, unscrew it and use a caliper to determine the actual distance from the support body to the end of the ball pin. If this distance is more than 11.8 mm, the support must be replaced or repaired. Removing the upper or lower ball joints can sometimes be very difficult. Neither the device recommended by the manufacturer nor such an ancient and proven tool as a hammer helps.
The most effective device was made by one of the car enthusiasts (fig. 60, a). It copes equally well with both the upper and lower ball joints. Before installing the device (fig. 60, b) necessary:
- securely fix the car;
- unscrew the three nuts securing the support to be removed to the lever and the self-locking nut from the ball joint.
When dismantling the lower support, the self-locking nut should initially be unscrewed only 2-3 threads, otherwise the threads may be damaged.
If you are performing the operation for the first time, you need to be on your guard, because sometimes when the parts are separated, a pop is heard and the upper support can jump up sharply. To avoid surprises, it is advisable to tie the upper support to the eye of the rotary stand with wire before pressing out.
Most car enthusiasts who repair their cars on their own have successfully mastered the repair of upper ball joints. The experience of a car enthusiast from Kursk allows him to try his hand at repairing the lower ball joint (Fig. 61), if necessary (i.e. there is no possibility to purchase a new one) and if it is appropriate (i.e. the housing 2 is intact and all other elements are not very worn: ball pin 1 and antifriction liner 4).
The sequence for restoring the lower ball joint is as follows:
- drill out the welding spots in housing 2 and separate it from the clamp 3;
- place a washer 6 made of sheet oil-resistant rubber 1.5–3.5 mm thick under the rubber heel 5, depending on the degree of wear of the hinge;
- assemble the hinge by connecting both parts of the body by welding.
Before installing new or repaired supports, do not forget to fill the space between the support and the rubber cover with SHRB-4 or Li-tol-24 grease.
When searching for knocks in the front suspension (Fig. 62), it is advisable to carefully examine the condition of the levers 1.8 and cross member 4 themselves. For a number of reasons, cracks may form on them, the presence of which is fraught with major troubles. In addition to shock absorbers 3 and ball joints 2 and 10, knocking in the suspensions can be created by the stabilizer 7 of transverse stability. This happens rarely, but it still happens. The fastening of rubber cushions 6 weakens, or they wear out. In the latter case, they must be replaced.
Considering that the need to replace one or more anti-roll bar cushions usually occurs after 100 thousand km of mileage, the main difficulty is to unscrew the nuts that fasten the 5th and 9th cushion clips to the front suspension arm or side member. Do not break into the open door, make the nuts pliable with a kerosene compress. Having unscrewed the nuts of the cushion clips that are subject to replacement, you can consider that 75% of the job is done. Having released the fastening, the stabilizer, due to its elasticity, will independently separate from the lower arm.
If one of the outer cushions needs to be replaced, a new rubber cushion with a bracket is put on the end of the stabilizer that has come off the lever and, pressing the end of the stabilizer to the lower lever, the nuts are tightened. When it is necessary to replace the cushion of one of the middle brackets, proceed as follows: unscrew the nuts securing the outer and middle brackets; remove the outer bracket with the cushion; tighten the middle bracket with the cushion; install a new cushion into the middle bracket, ensuring that the cushion protrusion fits into the bracket hole; put the middle bracket with the cushion assembly on the stabilizer. To make your job much easier, it is advisable to clean the stabilizer from dirt and unevenness, and then lubricate it with soap. To finally complete the operation, all that remains is to secure the middle bracket, put on and secure the outer one.
Increased clearances or wear of the wheel hub bearing. How to deal with this defect is described above.
The wheel balance is disturbed or the front suspension spring is broken. In this case, it is advisable to contact a service station, since a high-quality wheel balancing can only be done on a special stand. Special equipment is also needed to remove and install the spring. In this case, amateurish work is unacceptable. It is important to remember: a compressed front suspension spring is a high-energy accumulator.