The gas distribution system is one of the main components of any engine. It includes a chain or belt drive. The latter is less noisy, but at the same time less reliable. The chain never breaks. But at work it can make sounds. Today we will consider how the timing chain ZMZ-406 is replaced and what this element is.
Characteristic
This part is the basis of the engine. It is thanks to the chain that it is possible to correctly set the timing phases of ZMZ-406. Recall this inlet, compression, stroke and exhaust. In order not to bend the valve and ensure maximum efficiency, a special chain is used.
It is she who distributes the forces on the camshaft, which opens and closes the engine valves at the right time. Thus, the ZMZ-406 timing system ensures the timely supply of the combustible mixture into the combustion chamber and their output after the third step (working stroke). As a result, we get a powerful and economical engine.
Where is?
The timing chain ZMZ-406 is located on the crankshaft pulley. It rotates simultaneously with it when the engine is running. Also used are special timing chain stabilizers ZMZ-406. They provide the necessary tension mechanism.
If it becomes worthless, the installation of the timing phases ZMZ-406 will be carried out incorrectly. The chain will stretch or skip a few teeth. During the operation of the mechanism, a water pump, a hydraulic amplifier (not on all Gazelles) and an intermediate shaft of the ignition system are activated. The timing chain ZMZ-406 is closely connected with each of these elements.
About malfunctions with timing
The main signs of failure are a decrease in engine power, characteristic pops in the exhaust and intake manifold, as well as a low level of compression. It should not be less than 10 kilograms per square centimeter. But it is not necessary to buy a new timing kit ZMZ-406. Perhaps only the chain is out of order. By the way, when it malfunctions, it emits metal knocks. Such malfunctions of the timing belt ZMZ-406 can be provoked by a loose fit of the valve seats. As a result, carbon deposits are formed, valve springs fail. The gap between the beam and the valve stem is not normal. If the engine does not provide sufficient opening of the valves, this can cause damage to the hydraulic lifters. The gear of the crankshaft and camshaft also wears out. As a result, it is necessary to repair the ZMZ-406 engine. Timing is a serious mechanism. In order to avoid trouble, it is necessary to monitor the chain tension and adjust the damper. This must be done at least once every 80 thousand kilometers. A chain, unlike a belt, is a fairly reliable mechanism. It does not tear and does not provoke bending of valves, but only stretches during prolonged use. The resource of the gas distribution mechanism chain is about 200 thousand kilometers. The belt resource does not exceed 80 thousand. But if you have characteristic symptoms of 150 thousand (meaning metal chain knocks), do not hesitate to replace. Below we will look at how to repair this system with our own hands.
Instruments
For the replacement of the timing ZMZ-406 to be successful, we need to prepare a set of tools. We will need a set of heads and hex wrenches, a torque wrench, a hammer and a chisel. Next, we consider the step-by-step process of replacing the timing chain ZMZ-406.
Preparatory work
First we need to prepare containers for draining working fluids. First, pour the antifreeze. In "GAZelle" it contains a lot, about ten liters. It merges by unscrewing the plug at the bottom of the radiator. Be careful - first antifreeze will run a big pressure. As it pours out, it will be smaller. It is recommended to use a bulk canister or bucket. It is important that the container is clean. For a better yield of antifreeze, unscrew the cap on the expansion tank.
What next?
After that, remove the front apron with the radiator grille (if this is a “business" bumper, unscrew its fastenings in the center and on the sides). Next, remove all the clamps and pipes that are connected to the radiator. Dismantle the last element. If your car is equipped with a hydraulic booster, you must remove the power steering pump drive belt.
We also take out the generator belt and the pump, after loosening the tension. Now remove the cylinder head valve cover. All bolts must be folded into a separate box or niche. This will not affect the repair, but will significantly speed up the assembly process. You do not have to look for where the missing bolt or nut lies, as is often the case. Next, we unscrew the viscous coupling of the fan with the impeller itself.
It is recommended that the valve cover be placed in a clean and dry place. The presence of dust on its inner side is extremely undesirable. Next, the pump and the crankshaft rotation sensor are removed (do not forget to reinstall it, otherwise you just will not start the engine). At the next stage, the crankshaft pulley and the oil pan are dismantled. Then unscrew the two mounting bolts of the chain tensioner. The last element goes out. In total, on the 406th and 405th engines there are two hydraulic tensioners - upper and lower. We need to get both mechanisms. The lower one is disassembled by the same principle. Next, we need to remove the chain cover. It is mounted on seven bolts. Be careful - you can damage the front crankshaft oil seal and cylinder head gasket. We unscrew the bolt of the upper tensioner and remove the lever with an asterisk. Next, we unscrew the plastic timing chain stabilizer ZMZ-406. We unscrew the bolts securing the gears to the camshaft flange (there are two of them in this engine). Next we need another tool. To remove the lower gear, it is necessary to install a minus screwdriver (it will serve as a lever) between it and the second gear.
We bend the end of the locking plate, and, holding the intermediate shaft, insert our tool. We take out the gears and the lower part of the chain from the crankshaft. If it is difficult to disassemble, remove the rubber seal between the gear and the bushing. The last element is also dismantled. The second gear is compressed using a puller.
After you removed the chain
So, we get the element out. The chain must be thoroughly washed with gasoline and cleaned of dirt. Inspect her appearance. After 150 or more thousand kilometers, it stretches for 1-2 centimeters. This is quite enough to provoke incorrect gas distribution. If there are signs of wear, nicks and cracks on the mechanism bushings, the mechanism is not subject to further operation. If there are chips on the gears, we also replace them with new ones. Inspect condition of depressants. If damaged, replace the item with a new one. Check the condition of the tensioner sprockets. They should rotate freely on their axis. Scoring and chips on the working surface should not be.
Reverse assembly
First you need to set the timing correctly. To do this, scroll the crankshaft until the first mark on it coincides with the second on the cylinder block. The piston of the first cylinder must be in top dead center position. Next, install the chain damper. We do not tighten the bolts yet. Lubricate the lower chain with machine oil and put it on the driven gear and crankshaft. We install the penultimate one so that the pin enters the bore of the intermediate shaft. The mark on the gear should match the one on the cylinder block. In this case, the part of the chain that passes through the damper will be tensioned. We twist fixing bolts of gears of an intermediate shaft. A lock plate is installed under them.
Use of a torque wrench is recommended. Tightening force - from 22 to 25 Nm. When the bolt tightens with the right moment, this key will begin to snap - go to the second element. Do not forget to fix both bolts with a locking plate. We bend its edges with a hammer and a chisel. Next, click on the tensioner lever and check if the marks on the cylinder block and on the gear match. We tighten the bolts of the damper and lubricate the upper chain. We put it on the gear of the intermediate shaft. Scroll the camshaft clockwise. We put the chain on the second gear. The camshaft pin should enter its hole.
Charging moments and marks
Using a four-sided key, scroll the camshaft counterclockwise. We tighten the timing chain. The crankshaft and countershaft must not rotate. The marks will coincide with the upper surface of the cylinder head. We remove the gear from the exhaust camshaft and install a chain on it. Then we put it back, slightly turning the shaft clockwise. The pins should go into the pinion hole. We rotate the shaft counterclockwise, pulling the timing chain. Next, the chain cover and pump are installed. A small layer of sealant should be applied to the top of the cover. When installing, try not to damage the front crankshaft oil seal. Next, two hydraulic tensioners and a crankshaft pulley are mounted. At the latter, the tightening torque must be observed - from 104 to 129 Nm.
In this case, you need to engage 5th gear and the parking brake. Hold the crankshaft so that it does not crank. Then tighten the ratchet. The latter scrolls two turns. The crankshaft is set to top dead center (relative to the first cylinder). Next, the cylinder head cover is installed. A layer of sealant must be applied to it to prevent oil leaks. The cover is tightened with a torque of about 12 Nm. Next, you need to connect the crankcase ventilation pipe to the fitting on the valve cover. We connect wires to the ignition coils and put their ends on the candles. Fill the antifreeze back, put the radiator in place and start the engine. If everything was done correctly, metallic sounds will disappear, and engine power will return to normal. This completes the process of repairing the gas distribution mechanism . The best timing belt ZMZ-406 is the one that is on the chain. Many car owners are still skeptical of a belt drive. Chain drive is many times more reliable. But practice shows that every year it is losing popularity, especially among foreign manufacturers.
Installation issues
There have been cases when the repair of this mechanism damaged the head gasket. In this case, it is necessary to cut off its remains with a clerical knife and use a sealant. Also, with this tool it is necessary to process all the sealing parts of the cover. Sealant drying time - 24 hours.
Conclusion
So, we found out what the gas distribution mechanism on the GAZelevsky 406th motor is. As you can see, replacing the chain does not require additional tools. But in time it takes all day. Therefore, it is worth planning such repairs in advance. At the service station, such a service takes about 5 hours. Its cost is six thousand rubles. The gas distribution kit itself costs about five thousand. It includes chains (small and large), hydraulic tensioners, dampers and camshaft sprockets.