BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

What bearings are installed in your engine? Not all motorists answer such question intelligibly. One person, far from the equipment, told directly: "Here ten years go, but I do not know that they are there inside".

Nevertheless bearings are there. And not some, but quite certain. They are durable, but are not eternal and when fail, not to do without understanding of the main point. Well, and for professional repairmen it is simply ordinary matter.

As the bearing works

In modern automobile engines as support for cranked and camshafts almost only serve sliding bearings. Rolling bearings (ball, roller, needle) apply to the similar purposes only in small motorcycle motors.

Necessary operability of bearings of sliding is reached by use of so-called effect of an oil wedge. At rotation of a smooth shaft in a gap between shaft and an opening oil moves. As the loading operating on a shaft causes its excentric shift, oil as if drags on in the narrowed part of a gap and forms the oil wedge interfering contact of a shaft with opening walls. The more pressure and viscosity of oil in a gap, the big loading (before contact of surfaces) maintains the sliding bearing.

The actual pressure of oil in a zone of a wedge reaches 50–80 MPas (500–800 ^kg/cm2), and in some designs more. It is one hundred times higher, than in the giving system. However it is not necessary to think that giving pressure influences operation of the bearing a little. The it is more, the more intensively there is a pumping of oil via the bearing and the better it cooling.

Under certain conditions the operating mode with the minimum friction (it also call liquid) can be broken. It happens at ponizheniy to viscosity of oil (for example, because of its overheat owing to insufficient giving) and decrease in frequency of rotation at increase of loading.

Quite often, especially after repair of the engine, also the non-optimal geometry of knot affects. At an insignificant deviation of a form of surfaces from cylindrical, at a distortion of axes and other defects of details perhaps local increase of specific loading (that is the loading carried to surface area) above an admissible limit. Then the oil film in these parts becomes thin, and surfaces of a shaft and the bearing begin to adjoin on microroughnesses. There is a mode of semi-liquid lubricant which is characterized by increase of friction and a gradual warming up of the bearing. Further it can lead to so-called boundary friction with full contact of surfaces which consequence the overheat, skhvatyvany (teases), jamming, fusion and destruction of the bearing will be.

It is clear, that in operation the mode of boundary friction is unacceptable. Nevertheless it appears at oil supply violation, and it most often happens because of its shortage in a case, that is or owing to oversight of the driver, or at damage of the pallet of a case as a result of arrival on an obstacle.

The mode of semi-liquid lubricant is admissible only for a short time when it does not manage to affect wear of the bearing. An example – launch of the cold engine. However, there is other danger: at very low temperature oil of a mozheta to be too viscous and its normal giving is restored long (20–30 seconds and more). Here already semi-liquid lubricant is capable to affect wear of details considerably.

Improvement of automobile engines is connected with the constant growth of frequency of rotation and increase in power. Increase in compactness of designs, including reduction of width and diameter of bearings is at the same time observed. It means that specific tension grows in knot. And as load of the bearing during the operation of the engine cyclically changes in size and the direction, there is real a so-called fatigue failure of details. To provide operability of bearings in such conditions, special designs, materials and technologies are required.

As it is arranged

Usually bearings of bent shafts in modern engines carry out in the form of thin-walled inserts or plugs 1,0-2,5 mm thick (is rare more). Inserts of radical bearings of a bent shaft do to thickness because of need to place a circular flute for supply of oil to conrod bearings. The general tendency – reduction of thickness of inserts which averages 1,8-2,0 mm at radical and 1,4–1,5 mm at conrod bearings now. The inserts are thinner, the better they adjoin to the surface of the case (bed), the heat sink from the bearing, more precisely geometry, less admissible gap and noise during the work is better, the knot resource is more.

That at installation in a bed the insert precisely took its form, in a free state it has to have a tightness on diameter of a bed (so-called straightening) and not cylindrical form of variable radius. Besides, the tightness is necessary for a good prileganiye to a surface and deduction from a provorachivaniye and on insert length – it is called a vystupaniye. All these parameters depend on thickness, width and diameter of inserts, at the same time straightening averages 0,5–1,0 mm, and a vystupaniye – 0,04–0,08 mm. However for reliable operation of the bearing and it still is not enough. About the socket thickness of inserts is reduced by 0,010–0,015 mm to avoid zadir in these parts. They can appear because of deformation of an opening in the case under the influence of working loading when the working gap in the bearing is small.

Materials for inserts can be different. Their choice coordinates with material of a bent shaft and its heat treatment, degree of a forsirovka of the engine and the set resource. To a certain extent also traditions of automobile firm affect here.

Inserts always do multilayered. An insert basis – a steel tape which provides durability and reliability of landing in the case. Apply with various ways a layer on a basis (or layers) special antifrictional material 0,3-0,5 mm thick. The main requirements to antifrictional material – low friction on a shaft, the high durability and heat conductivity (that is it is good to carry out ability warmly from a surface to the bearing case). The first requirement soft metals best of all provide, for example, alloys with high content of tin and lead (in particular, widely known babbits).

In the past babbits were widely applied on the low-forced low-reverse engines. With growth of loadings durability of such inserts with a thick layer of babbit was insufficient. The problem was solved by replacement of all this layer by a peculiar sandwich – the svintsovoolovyanisty bronze covered thin (0,03–0,05 mm) a layer of the same babbit. The insert became multilayered. In modern stalebronzobabbitovy engines inserts usually carry out 4-layer (under babbit very thin underlayer of nickel still lies) and even 5-layer when for improvement extra earnings from above the thinnest layer of tin is applied on a working surface. Quite so bearings on many foreign engines look.

Along with it also steel-aluminum inserts were widely adopted. As antifrictional material serve aluminum alloys with tin, lead, silicon, zinc or cadmium, both with coverings, and without them here. Most often in world practice aluminum alloy from 20% of tin without covering is used. It well resists to high loadings and speeds of rotation of modern engines, including diesels, and at the same time has satisfactory "softness". Nevertheless steel-aluminum inserts are more rigid, than babbitovy (or with a babbitovy covering) therefore are more inclined to teases in the conditions of insufficient lubricant.

Auxiliary and camshafts of engines rotate, as a rule, with a smaller frequency, than cranked and experience much smaller strain therefore it is easier than a condition of their work. Inserts and plugs of these shaft usually do of the materials similar by the aforesaid. Besides, here sometimes apply babbit or bronze without covering. Often these bearings have no plugs or inserts at all and are formed directly by boring of openings in a head of the block of cylinders. In such designs the head is made of aluminum alloy with silicon which has quite good antifrictional properties.

The general for bearings of modern engines, especially if it is about support of bent shafts, compliance of material and a design of inserts to material and operating conditions of a shaft is (frequency of rotation, loading, lubricant condition etc.). Therefore any replacement of details when, for example, at repair put inserts from other engine, cannot be recommended. Otherwise durability of the repaired unit can turn out very small. To make up the mind to such step, it is necessary to have the relevant information.

Inserts are very exact (precision) details. To guarantee small (but quite concrete – on average 0,03–0,06 mm) working gaps in bearings, at production maintain thickness of an insert with an accuracy about 5-8 microns, and length – 10–20 microns. Violation of these requirements can lead to change of a working gap in the bearing or density of landing of an insert in the case that is inadmissible because of decrease in reliability and a resource of all engine in general.

Who makes them

Complexity of all circle of the problems connected with creation of high-quality automobile bearings of sliding led to the fact that their production gradually passed to specialized firms. Abroad many their such firms at the same time release also other details of engines, and deliveries go both on conveyors of automobile works, and to spare parts. Some firms such are a part of the known multinational production and commerce and industry corporations. From world manufacturers of bearings for engines it should be noted Kolbenschmidt (KS), Glyco, TRW, Sealed Power, Glacier, Clevite, Bimet first of all. In recent years bearings began to do also such firms – "coryphaeuses" as Mahle and Goetze. Among "young people" it is worth mentioning the specialized King (Israel) which began release of bearings in the early eighties.

Most of the listed producers issues the huge nomenclature of bearings and delivers the production in the spare part everywhere including on our market (through dealers or the wholesale trading companies). Generally of course, it is bearings for foreign engines – European, Japanese and American.

It is possible to find inserts in sale as standard, and various repair sizes (as a rule, no more than 0,75 mm) on the majority of the widespread models "Audi Volkswagen", BMW, "Mercedes", "Ford", "Opel", "Fiat", "Toyota", "Nissan", "Mitsubishi", "Mazda" etc. On less widespread models, and also in need of purchase of inserts of the bigger repair size usually it is necessary to make out the order and to wait on average for 5-10 days (at different trading companies these terms are various).

Quality of such production usually does not raise doubts neither on geometry, nor on materials. Though if there is a choice and doubts in what firm manufacturer to give preference, it must be kept in mind the following. Such firms as, for example, Kolbenschmidt, Glyco, Glacier are one of the main suppliers of mass production. Upon purchase of their products it is possible even to receive the same inserts that stood on the engine "since the birth". The difference will be only in absence on new details of an emblem of firm manufacturer of the car. By the way, search of "family" (or so-called original) inserts of the repair sizes can be problematic. Not all automobile firms deliver repair inserts in the spare part and the price of inserts in "original" packing is, as a rule, much higher, than directly from their producer.

Inserts of other, less eminent firms are usually cheaper though on quality it is difficult to find differences. Moreover, if there is a choice, then here it is possible to try to consider also service conditions of the car. So, rather cheap inserts, strangely enough, resist to the low-quality oils and oil filters "walking" on our shops and the markets than more expensive stalebronzobabbitovy slightly better. It was shown, in particular, by practice of use under repair of steel-aluminum inserts of King instead of regular bronzobabbitovy – such replacement does not cause damage to reliability of engines, but allows to save considerably.

Some of the listed firms release inserts and for our cars. In our market it is already possible to find these products for engines VAZ of production of Clevite, Bimet and Glacier. Certainly, they it is notable more expensively than domestic. However you should not save comparison on inserts at repair of domestic motors. Domestic usually does not bear with import production. Deviations on thickness at some of our commodity copies reach 25–30 microns instead of 8 microns regulated by the admission. As a result after a zazhatiya a cover внутрення the surface of the bearing gains irregular shape at which, for example, the gap in 0,07–0,09 mm in one section of the bearing can even pass into a tightness in another.