To all good day... In today's article we are considering a typical problem - the oil pressure in the ZMZ 406 engine has disappeared. Unfortunately, this is a fairly common problem and there are quite a few typical reasons in the article, we will analyze all the reasons and how they manifest themselves.
Let's start with a description of the design of the ZMZ 406 lubrication system:
The oil pump is driven from the intermediate shaft through a hexagon. The oil pump has a pressure reducing valve that relieves excess oil pressure back into the crankcase. From the oil pump, oil is fed through a filter to the main oil line, from which the journals are lubricated crankshaft, and bushings of the intermediate shaft of the timing drive. Also from the main highway there is a channel to the cylinder head and to the hydraulic tensioners. In the cylinder head, 2 oil channels are drilled parallel to the camshafts. These channels supply oil to each camshaft journal and to each of the 16 hydraulic lifters.
Most problem areas in the lubrication system - a pressure reducing valve, intermediate shaft bushings and hydraulic chain tensioners, but first things first ...
Oil pressure in the ZMZ 406 suddenly disappeared.
There are only two reasons in this case - the oil pump pressure relief valve is stuck in the open position. It looks like this:
This happens, usually, due to dirt getting under the pressure reducing valve. Even the smallest crumb wedges the valve and it does not close completely.
The second typical reason is a breakdown of the oil pump drive.
The drive looks like this:
It should be noted that these two malfunctions are extremely rare and occur when the oil change interval is not observed and when operating on oil that does not correspond to the climate.
The oil pressure in the engine dropped gradually.
This is the most typical problem, it is associated with normal wear and tear, periodicity of maintenance and design errors.….
The most common reason is the oil filter.
During the operation of the gazelle (2705), I changed the filter every 5000 km, and changed the oil every 10,000 km. The reason is that when operating on gasoline, the oil quickly darkens and a heap of dirt forms in it that clogs the filter. When operating on gas, this problem is not observed!
The second most popular reason is the ingress of gasoline into the fuel.
Basically, the proportion of carburetor versions of the 406 engine is fair (when the gasoline pump membrane breaks, gasoline inevitably enters the oil), but also on injection engine with a traveling nozzle, this is a perfectly possible scenario.
The third reason is wear and tear.
Due to wear, all the gaps in the friction pairs gradually increase.
- The main place where pressure is lost is the intermediate shaft. Many do not change the intermediate shaft support bushings even when overhaul but it is in these bushings that most of the pressure is lost.
- The second most popular place is the worn out hydraulic chain tensioners.
- Third place - cylinder head wear and wear camshafts.. The fact is that on the 406 engine, the camshaft beds are located in the body of the cylinder head and at the slightest "drift" of the plane, the wear of the bed increases significantly - the result is a pressure loss. With the wear of the shaft itself, the gap in the friction pair increases and the pressure is also lost.
- The fourth place is the wear of the oil pump. When worn, the pump will not pump enough oil into the engine lubrication system and there will be no oil pressure. You can deal with this by rebuilding the pump with the output of its planes or replacing the oil pump assembly with an oil pump from ZMZ 514 (it is for a diesel engine and has increased performance).
- Fifth place - hydraulic compensators for valve clearances, expansion joints in the cylinder head 16 (by the number of valves) and at high mileage their beds are also subject to wear and tear, but the service life of the expansion joint beds, as a rule, exceeds the service life of the cylinder head.
The fourth reason is the oil bypass valve springs.
A bypass valve is installed on the oil pump housing, it opens at high oil pressure. The fact is that over time, the valve springs weaken and some of the oil pressure is lost on this valve. It's okay if you place a couple of washers under the valve spring when overhauling the pump.
About the oil cooler.
On some modifications of the ZMZ 406, a radiator is installed for cooling the oil, but in fact this design is practically not used since it reduces the pressure of the already liquefied oil and has low-quality taps that are constantly running. Relatively competently, the oil cooler is implemented at ZMZ 405 (a thermal valve is used), but even there its effectiveness is questionable. In most cases, it is advisable to muffle the oil cooler and use a more thermostable oil (tested on personal experience with gas 2705 with a mileage of 470,000 km).
Ways to increase the oil pressure in the ZMZ 406 engine during operation.
- More frequent replacement oil filter.
- Replacing the oil pump with a pump from ZMZ 514, part number 514 .1011010
- Disconnecting the oil cooler or replacing it with a heat exchanger.
- Replacing the oil with a thicker and higher quality one, it is the viscosity at high temperatures that is important.
- Placing 2-3 washers under the oil bypass valve spring
Ways to increase oil pressure during overhaul.
Be sure to reverse the countershaft and turn the bushings correctly.
Install the jets in the lubrication system.
The fact is that there are several places in the engine where a lot of pressure is lost, and in order to increase the engine's service life during a major overhaul, it makes sense to plug some channels in the lubrication system with carburetor jets! The best option turned out to be jets reamed with a 2 mm drill.
So, here are these places and options for their jetting:
Oil pump shaft lubrication hole
Hydraulic chain tensioners (upper and lower)
That's all for me. I hope that the problem of missing oil pressure in the 406 engine will never bother you again.
The ZMZ-406 lubrication system consists of an oil level indicator, an oil pump with an oil receiver, oil channels, an oil filter, pressure reducing valve, oil purification filter, oil pan, oil filler cap, oil cooler, safety valve and shut-off valve.
The lubrication system of the ZMZ-406 engine is combined: the main and connecting rod bearings of the crankshaft, piston pins, camshaft bearings, bearings of the intermediate shaft and the oil pump drive shaft, hydraulic pushers and helical gears are lubricated under pressure. Other parts are spray lubricated.
The oil pump is gear-type, single-section driven from the intermediate shaft by means of a pair of helical gears. An oil cooler and a full-flow filter are integrated into the lubrication system. The oil level indicator has marks: the highest level "P" and lower level"O". The oil level should be close to the "P" mark, not exceeding it.
Oil can be delivered to work surfaces under pressure, spray and gravity. The choice of the method of supplying oil to a particular part depends on the conditions of its operation and the convenience of supplying lubricant. V car engines a combined lubrication system is used, in which lubricant is supplied to the most loaded parts under pressure, and to the rest of the parts by spraying and gravity.
Oil path from pump to timing valve assembly
A gear-type oil pump is installed inside the oil sump and is attached to the cylinder block with two pins. The pump body is made of aluminum alloy, the pump cover is made of cast iron, the pump gears are made of cermet. The drive gear is pinned to the shaft, the driven gear rotates freely on an axis pressed into the pump housing.
A 0.3 mm thick cardboard sealing gasket provides the required clearance between the ends of the gears and the cover. An oil receiver with a grid is attached to the lid of an aluminum alloy cast. A pressure reducing valve is located in the pump housing. Oil from the pump through the channels in the cylinder block and the outer tube on the left side of the block is supplied to the oil filter.
From the oil filter through the channels in the block, oil is supplied to the crankshaft main bearings and bearings camshaft, from the main bearings of the crankshaft through channels in the crankshaft, oil is supplied to the connecting rod bearings, and from the camshaft bearings through channels to the cylinder head for lubricating the rocker arms and upper tips of the rods.
A plunger-type pressure reducing valve is located in the oil pump housing and is factory-adjusted with a calibration spring. The adjustment should not be changed during operation. The oil pressure is determined by a pointer, the sensor of which is screwed into the oil line of the cylinder block.
In addition, the system is equipped with an emergency oil pressure indicator, the sensor of which is screwed into the lower part of the oil filter housing. The emergency oil pressure indicator lights up at a pressure of 0.4 ... 0.8 kgf / cm 2.
The oil pump is driven from the camshaft by a pair of helical gears. The drive gear is steel, cast into the camshaft body, the driven gear is steel, nitrocarburized, fixed with a pin on the shaft rotating in a cast iron housing. On the upper end of the shaft, a bushing is put on and fixed with a pin, which has a slot shifted by 1.5 mm to the side for driving the ignition distributor sensor. An intermediate hexagonal shaft is pivotally connected to the lower end of the shaft, the lower end of which enters the hexagonal hole of the oil pump shaft.
The shaft in the drive housing is lubricated with oil, which is sprayed by the moving parts of the motor. The splashed oil, flowing down the block walls, enters the slot - a trap at the lower end of the body shank and through the hole enters the shaft surface.
The shaft hole in the housing has a helical groove, due to which the oil is evenly distributed over its entire length when the shaft rotates. Excess oil from the upper cavity of the drive housing flows back into the crankcase through a channel in the housing. The drive gears are lubricated by a jet of oil flowing from a 2 mm hole in the cylinder block and connected to the fourth camshaft bearing, which has an annular groove.
Oil purification filter - full-flow, with a cardboard replaceable element, located on the left side of the engine. All the oil pumped into the system by the pump passes through the filter. The filter consists of a body, a cover, a center rod and a filter element.
In the upper part of the central rod there is a bypass valve, which, when the filter element is clogged, passes oil, bypassing it, into the oil line. The resistance of a clean filter element is 0.1 ... 0.2 kgf / cm2, the bypass valve starts to bypass oil when the resistance increases as a result of filter clogging up to 0.6 ... 0.7 kgf / cm2.
The oil cooler serves for additional cooling of the oil during the operation of the car in summer, as well as during prolonged driving at speeds above 100-110 km / h. The oil cooler is connected to the engine oil line by means of a rubber hose through a stopcock and a safety valve, which are installed on the left side of the engine.
The position of the tap handle along the hose corresponds to the open position of the tap, across - to the closed one.
The safety valve opens the passage of oil to the radiator at a pressure above 0.7 ... 0.9 kgf / cm 2. The oil from the radiator is drained through a hose through the timing gear cover (on the right side of the engine) into the crankcase.
The crankcase ventilation is closed, forced, acting as a result of a vacuum in the intake manifold and in the air filter. When the engine is running on Idling and at partial loads, gases from the crankcase are sucked into the intake pipe, at full loads - into air filter and an inlet pipe.
Lubrication diagram in cross-section of the engine
Figure 7 - Cross section of the ZMZ 406 engine (lubrication diagram)
1 - oil pump; 2 - oil sump; 3 - oil pump bypass valve;
4 - thermal valve; 5 - central oil line; 6 - oil filter;
7, 8, 10, 11, 12, 14, 17, 18, 19 - oil supply channels; 9 - fitting of the thermal valve to drain the oil into the radiator; 13 - cover of the oil filler pipe; 15 - handle of the oil level indicator;
16 - oil pressure alarm sensor; 20 - crankshaft;
21 - rod oil level indicator; 22 - hole for connecting the fitting of the hose for supplying oil from the radiator; 23 - oil drain plug
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Pressure reducing valve- plunger type, located in the inlet pipe of the oil pump. The valve plug is made of steel; to increase the hardness and wear resistance of the outer working surface, it is subjected to nitrocarburizing.
The pressure reducing valve is adjusted at the factory by selection of 3 washers of a certain thickness. It is not recommended to change the valve adjustment during operation.
Oil pump drive- carried out by a pair of helical gears from the intermediate shaft 1 of the camshaft drive.
On the intermediate shaft using a segmented key 3, a drive gear 2 is installed and secured with a flange nut.
A steel sleeve 6, which has an internal hexagonal hole, is pressed into the upper part of the driven gear.
A hexagonal shaft 9 is inserted into the hole of the bushing, the lower end of which enters the hexagonal hole of the oil pump shaft.
From above, the oil pump drive is closed by a cover 4, secured through a gasket 5 with four bolts.
The driven gear when rotating by its upper end surface is pressed against the drive cover.
The drive and driven helical gears are made of ductile iron and nitrided to improve their wear resistance.
The hexagonal roller is made of alloy steel and carbon nitrated. The drive roller 8 is steel, with local hardening of the supporting surfaces by high-frequency currents.
Oil filter- full-flow single-use oil filters of non-separable design are installed on the engine.
Filters 2101C-1012005-NK-2 and 406.1012005-02 are equipped with a bypass valve filter element, which reduces the likelihood of crude oil entering the lubrication system when starting a cold engine and maximum contamination of the main filter element.
Oil purification filters 2101C-1012005-NK-2 and 406.1012005-02 work as follows: oil through the holes in the cover 7 under pressure is fed into the cavity between the outer surface of the main filter element 5 and the body 2, passes through the filter curtain of element 5, is cleaned and enters through the central hole of the cover 7 into the central oil line.
In case of extreme contamination of the main filter element or cold start, when the oil is very thick and hardly passes through the main filter element, the bypass valve 4 opens and the oil flows into the engine, being cleaned by the filter element 3 of the bypass valve.
The anti-drain valve 6 prevents oil from leaking out of the filter when the car is parked and the subsequent "oil starvation" at start-up.
The filter 406.1012005-01 is designed similarly to the oil filters presented above, but does not contain the filter element 3 of the bypass valve.
The oil filter must be replaced at TO-1 (every 10,000 km of run) simultaneously with the oil change.
Thermal valve- designed for automatic feed control
oil into the oil cooler depending on the oil temperature and its pressure. On the engine, a thermal valve is installed between the cylinder block and the oil filter.
The thermal valve consists of a body 3, cast from an aluminum alloy, two valves: a safety valve, consisting of a ball 4 and a spring 5, and a bypass valve, consisting of a plunger 1 controlled by a thermal power sensor 2 and a spring 10; threaded plugs 7 and 8 with gaskets 6 and 9. The oil supply hose to the radiator is connected to the fitting 11.
From the oil pump, oil is supplied under pressure to the cavity of the thermal valve A. When the oil pressure is above 0.7 ... 0.9 kgf / cm, the ball valve opens and the oil enters the channel of the thermal valve body B to plunger 1.
When the oil temperature reaches 81 ± 2 ° C, the piston of the thermal power element 2, washed by a stream of hot oil, begins to move the plunger 10, opening the way for the oil flow from channel B to the oil cooler.
The ball valve protects the rubbing engine parts from an excessive drop in oil pressure in the lubrication system.
Any engine internal combustion lubrication of rubbing parts is necessary, and engines of the ZMZ family are no exception in this regard. Without constant lubrication, such an engine will work for a maximum of an hour, after which it will simply jam. Its cylinders and valves will be seriously damaged, and it will be extremely difficult to repair such damage. Therefore, the oil pressure in the ZMZ engine is the most important indicator that the car owner must carefully monitor. But on domestic cars with ZMZ motors, oil pressure very often disappears. Let's try to figure out for what reasons this happens and how it can be eliminated.
About ZMZ engines
Before talking about oil pressure, it is worth introducing the reader to the engine itself. ZMZ engines are produced by the Zavolzhsky Motor Plant. They have 4 cylinders and 16 valves.
ZMZ engines are produced by the Zavolzhsky Motor Plant
These motors are installed on Volga, UAZ, GAZelle, Sobol cars. The family includes motors ZMZ-402, 405, 406, 409, 515 and a number of their special modifications. ZMZ engines have their advantages:
- good maintainability;
- simplicity of the device;
- low demands on the quality of fuel.
But there are also disadvantages:
- the timing drive is very cumbersome;
- the reliability of the chain tensioner in the timing drive leaves much to be desired;
- piston rings have an archaic design. As a result, large lubricant losses and power drops are observed;
- the overall quality of casting and heat treatment of individual engine parts is getting worse every year.
Oil pressure rate in ZMZ engines
The pressure in the lubrication system is measured only when the engine is warm and idling. The crankshaft rotation speed at the time of measurement should not exceed 900 rpm. Here are the ideal oil pressure rates:
- for motors ZMZ 406 and 409, a pressure of 1 kgf / cm² is considered ideal;
- for motors ZMZ 402, 405 and 515, the ideal pressure is 0.8 kgf / cm².
It should also be noted here that highest pressure in the lubrication system of the ZMZ engine, theoretically, it can reach 6.2 kgf / cm², but in practice this almost never happens. As soon as the oil pressure reaches 5 kgf / cm², the pressure reducing valve in the motor opens and the excess oil goes back to the oil pump. So the oil can reach the critical point only in one case: if the pressure reducing valve is stuck in the closed position, and this happens extremely rarely.
Checking the oil pressure
Oil pressure is displayed on dashboard car. The problem is that it is far from always possible to trust these numbers, since the devices can also fail and begin to give incorrect readings. It often happens that the oil pressure is normal, but the instruments show that there is no pressure at all. For this reason, it is advisable to simply inspect the vehicle. Here's how to do it:
If all of the above measures did not work, and the reason low pressure not identified, the last way remains: use an additional pressure gauge.
Signs of a drop in oil pressure
If the oil pressure in the engine drops sharply, it is impossible not to notice it. Here are the main signs that something is wrong with the engine lubrication system:
- the motor began to overheat quickly. At the same time, the exhaust gas becomes larger, and the exhaust has a black color, which is especially noticeable when the car picks up speed;
- bearings and other parts subject to intense friction began to wear out very quickly;
- the engine began to pound and vibrate. The explanation is simple: there is little lubrication in the motor, the rubbing parts gradually wear out and the gaps between them increase. In the end, the details become loose, begin to knock and vibrate;
- the smell of burning in the cabin. If the oil pressure is lowered, it begins to oxidize at a faster rate and burns out. And the driver smells the combustion products.
Reasons for lowering oil pressure and their elimination
First of all, it should be noted that a drop in oil pressure is a malfunction, which is a common "disease" of all engines of the ZMZ family, regardless of their model. There are no special nuances associated with this malfunction and characteristic of any particular engine from the ZMZ family. For this reason, below we will consider the reasons for the drop in oil pressure in the ZMZ-409 engine, which is currently the most popular in our country. Here it should be said that the most common reason for a drop in oil pressure is an incorrect viscosity coefficient, aka SAE. Due to this driver error engine oil may become too liquid in hot weather. Or vice versa, in severe frost, it can quickly thicken. Therefore, before looking for a problem in the engine, the car owner should ask himself a simple question: did I fill in the oil?
A sharp drop in engine oil
If the oil pressure in the ZMZ engine drops sharply, then this can happen for two reasons:
It should be noted here that the above breakdowns are quite rare. For this to happen, the driver must absolutely "start" the engine and not change the oil in it for years, or use a lubricant that is not suitable in terms of viscosity for a long time.
Gradual drop in oil pressure
This problem is very common in all engines of the ZMZ family, without exception. It can arise due to many factors: these are design errors, which were mentioned above, and improper maintenance, and natural wear of parts, and much more. Here are the most common causes of a gradual drop in oil pressure:
- oil filter wear. Gazelle drivers strongly recommend changing these filters every 5-6 thousand km, and changing the oil every 10 thousand km. If this is not done, a dirty sludge forms in the oil, no matter how good it is, which gradually clogs the oil filter. And the driver at this moment observes the above signs of a drop in oil pressure;
Oil filters on motors ZMZ should be changed as often as possible
- general engine wear. First of all, this applies to the intermediate shaft, on which the main pressure losses take place. This is due to wear on the shaft support sleeves. The hydraulic chain tensioner can also wear out, which also does not differ in durability. In addition, the cylinder head itself and the camshafts are often worn out. At the slightest wear in this system, the pressure begins to drop, and the oil consumption gradually increases. A worn-out oil pump, which is simply not able to supply a sufficient amount of lubricant to the motor, can also cause a pressure drop. And finally, hydraulic lifters on the valves can fail, which also reduces the lubricant pressure. There is only one solution to all of the above problems: engine overhaul;
- wear of the pressure reducing valve. There is a spring in the pressure reducing valve that can weaken over time. As a result, part of the oil goes back to the oil pump, which leads to a decrease in oil pressure. Some motorists solve the problem simply: they put a couple of small washers under the spring in the valve. But this, as you might guess, is only a temporary measure. And the only correct solution is to replace the pressure reducing valve with a new one (it will not work to purchase a new spring for the valve - they are not sold separately);
The spring is the main component of the pressure reducing valve in the ZMZ motor
- oil cooler leak. Radiators, in which the oil is cooled, are on many cars with ZMZ engines. However, these radiators are used extremely rarely, as their quality leaves much to be desired. Of particular note is the oil cooler tap. This tap is constantly leaking. Solution: refuse to use an oil cooler, because when correct selection oil, the need for this device simply disappears. Or the second option: put a high-quality valve on the radiator (preferably a ball valve, made in Germany, but by no means Chinese).
Video: looking for the cause of the drop in oil pressure in the ZMZ engine
So, there are many reasons causing a drop in oil pressure in engines of the ZMZ family. Some of them are the result of "congenital diseases" of this motor. Others are the result of the driver's own carelessness, and still others are the result of banal mechanical wear and tear. Most of these problems can be eliminated on their own, but the overhaul of the motor will have to be entrusted to a qualified specialist.
The lubrication system is combined, with the supply of oil to the rubbing surfaces under pressure and spray and automatic control of the oil temperature by a thermal valve. Hydraulic valve lifters and chain tensioners are lubricated and operated under oil pressure.
The lubrication system includes: oil sump, oil pump with suction pipe and pressure reducing valve, oil pump drive, oil channels in the cylinder block, cylinder head and crankshaft, full-flow oil filter, oil dipstick, thermal valve, oil filler cap, oil drain plug and oil pressure sensors.
Oil circulation is as follows.
Pump 1 sucks in oil from the crankcase 2 and supplies it to the thermal valve 4 through the channel of the cylinder block.
At an oil pressure of 4.6 kgf / cm 2, the pressure relief valve 3 of the oil pump opens and the oil is bypassed back to the pump suction zone, thereby reducing the pressure increase in the lubrication system.
The maximum oil pressure in the lubrication system is 6.0 kgf / cm 2.
At an oil pressure above 0.7 ... 0.9 kgf / cm 2 and a temperature above plus 81 + 2 ° C, the thermal valve begins to open the passage to the oil flow into the radiator, which is discharged through the nozzle 9.
The temperature of the full opening of the thermal valve channel is plus 109 + 5 ° С. Cooled oil from the radiator returns to the oil sump through hole 22. After the thermal valve, the oil flows to the full-flow oil filter 6.
The cleaned oil from the filter enters the central oil line 4 of the cylinder block, from where it is fed through channels 18 to the main bearings of the crankshaft, through channels 8 - to the intermediate shaft bearings, through channel 7 - to the upper bearing of the oil pump drive shaft and is also supplied to the lower hydraulic tensioner camshaft drive chains.
From the main bearings, oil through the internal channels 19 of the crankshaft 20 is supplied to the connecting rod bearings and from them through the channels 17 in the connecting rods it is supplied to lubricate the piston pins.
To cool the piston, oil is sprayed onto the piston crown through a hole in the upper connecting rod head.
From the upper bearing of the oil pump drive shaft, oil is supplied through the cross bores and the inner cavity of the shaft to lubricate the lower shaft bearing and the bearing surface of the driven gear of the drive.
The oil pump drive gears are lubricated by a jet of oil sprayed through a hole in the central oil line.
From the central oil line, oil through channel 10 of the cylinder block enters the cylinder head, where it is fed through channels 12 to the camshaft supports, through channels 14 to the hydraulic pushers, and through channel 11 to the hydraulic tensioner of the upper camshaft drive chain.
Leaking out of the clearances and flowing into the oil sump at the front of the cylinder head, oil enters the chains, tensioner arms and camshaft sprockets.
At the rear of the cylinder head, oil flows into the oil sump through a hole in the head through a hole in the tide of the cylinder block.
Filling of oil into the engine is carried out through the oil filler pipe of the valve cover, which is closed by a cover 13 with a sealing rubber gasket.
The oil level is controlled by the marks on the oil level indicator 21: the upper level - “MAX” and the lower one - “MIN”.
The oil is drained through a hole in the oil crankcase, closed by a drain plug 23 with a gasket.
Oil cleaning is carried out by a mesh installed on the intake manifold of the oil pump, filter elements of a full-flow oil filter, as well as by centrifugation in the crankshaft channels.
Oil pressure control is carried out by the emergency oil pressure indicator (indicator lamp on the instrument panel), the sensor 16 of which is installed in the cylinder head.
The emergency oil pressure indicator lights up when the oil pressure drops below 40 .. .80 kPa (0.4 .. .0.8 kgf / cm 2).
Oil pump- gear type, installed inside the oil sump, attached with a gasket with two bolts to the cylinder block and a holder to the cover of the third main bearing.
The driving gear 1 is fixedly fixed on the roller 3 by means of a pin, and the driven gear 5 rotates freely on the axis 4, which is pressed into the pump housing 2.
At the upper end of the roller 3, a hexagonal hole is made, into which the hexagonal roller of the oil pump drive enters.
The centering of the pump drive shaft is achieved by seating the cylindrical protrusion of the pump housing in the cylinder block bore.
The pump body is cast from an aluminum alloy, the baffle 6 and gears are made of cermet.
An inlet pipe 7 with a mesh, in which a pressure reducing valve is installed, is fastened to the body with three screws.
