Replacing the bottom of a VAZ 2109 with your own hands

The metal frame 2109 is a supporting structure of the hatchback type with five doors. The unified body was created on the basis of the VAZ 2108, but most of the parts have different sizes. Both models have solid frames and attachments.

The body parts of 2109 are connected by spot welding, and areas of high load are reinforced by electric arc welding. For their production, sheet steel with a thickness of 0.7–1 mm is used. Small parts are stamped from thicker steel.

The body structure of the VAZ 2108 is all-metal welded, three-door type. Available in passenger and cargo-passenger versions. The “nine” has a five-door body, the internal and external side panels are equipped with openings for doors. Otherwise, the 2109 frame does not differ from the 2108.

The problem of domestic cars

Car body repair begins with the selection of tools. I’ll say right away that the list will be quite large, because the work is labor-intensive and requires a large number of devices, including electronic and gas models. We will need at least three types of hammers of different sizes, a flap wheel and a sanding wheel (it removes paint and light rust well).

VAZ 2109

A grinder will also come in handy, a 10 cubic meter carbon dioxide cylinder, a welding machine with a maximum current of 150 amperes, several chisels, and a set of metal drills. You can’t do without a jack here either; it’s better to have two of them.

Stock up on cutting wheels of approximately 1-2 millimeters and one cleaning wheel. Any type of jigsaw will do. Brush with rust converter, fiber disc (can be replaced with a simple budget brush). Standard driver's set, 2mm cord and plumb line. It seems that I have listed everything that is needed. It's time to get to work.

Features of some VAZ body parts

Ever since people began to use metal structures in the production of vehicles, corrosion, which leads to serious losses, has attracted the attention of researchers. It was from this time that the production of anti-corrosion materials began, which significantly help to extend the life of body metal parts.

But whatever one may say, time takes its toll. Not only small, but sometimes even large body parts have to be replaced, since rust literally eats through the part completely. In general, the poor condition of the body is distinguished by many subtle aspects. For example, individual parts of the body rust at different rates, which is explained by different operating conditions.

Bottom: weaknesses and methods of protection

We conclude: the most vulnerable areas of the body are the areas that most often come into contact with the moisture and mud environment. They are also the ones under the most pressure. In particular, these are the floors of VAZ cars, welds and other areas with the help of which the entire structure retains its original shape.

Let's consider the welded seams of the floor of any VAZ model, for example, Oka 1111. Microcracks already exist in such areas, since it is impossible to fasten the metal to each other flawlessly, no matter what kind of welding is used. Moisture gets into these very cracks.

Removing rotten parts

We begin repairs by removing rotten, rusty and deformed parts. I will describe the process using the example of a car, a VAZ 2109, which I was tasked with repairing. First, I’ll give you my problem areas in the car. The front floor of the car is completely rotten with all the jacks and reinforcements. And the jack could only be used with a sub-engine beam. The rear floor was also rotted. Corrosion also affected the car doors. In general, the bottom was almost absent. The wings were not in the best condition.

The front hood was noticeably rusty, all the floor connectors and the floor of the gas tank and spare tire were missing. The same fate befell the reflectors of almost all headlights. The front spar burst in the gearbox area. And above the muffler, in the floor of the trunk, there was a huge hole. The corners of the door were “eaten” by corrosion.

I describe in detail the condition of my car so that car enthusiasts can identify similar faults in theirs and draw the right conclusions. Once the necessary tools for car body repair are at hand, we begin installation.

Body repair is a harsh thing, or use a chisel to “CHISEL”

For everything about garage welding of rotten cars, see the new book on car repair from Khoma

In August 2009, a nice young lady approached me with a small request - to weld a hole in the side member of a VAZ-21093 car, in common parlance - “chisels”, they say, the husband is a diagnostician, “fumbles” with engines at 10c plus, but there is no one to do auto body work.

Well, helping your neighbor is a sacred thing, I thought and invited them to the show. The initial examination raised a lot of questions, ranging from year of birth to:

WHERE IS THE CAR'S FLOOR? Brief questioning of the owner revealed the following: the car was produced in 1996, stupidly stood in a pit for three years, after which it was bought outbid, hastily patched up, coated with various mastics and successfully sold off to the current owners, and since the diagnostician husband figured out that the engine was in good condition, he didn’t bother with the condition of the body…..But in vain!

The young lady was offered the following options:

— replace the floor, sills, rear side members

— completely change the body (the engine is excellent)

- cover it up again and sell it off to other less fortunate buyers at an even lower price (there was no recycling program at that time).

Ultimately, the decision was made - COOK!

Disassembling the interior took two hours, they opened the Shumka and “rejoiced”:

the floor of the car was practically destroyed by corrosion (see photos 1, 2, 3) The place of the “happy” driver, who almost ran along the “path with his own legs” (photo 4) looked especially impressive

Since the floor tunnel miraculously survived, only the “trough” was replaced

After cutting off the rags, cleaning off mastics and other offal, drilling out resistance welds on the side members, and carefully marking them, welding of the floor began.

By the way, everything was cooked using a domestic carbon dioxide semi-automatic PDG-165.

Next in line were the rapids.

After opening the outer panels, a view appeared no less gloomy than the appearance of the floor (photo 9, 10)

In order not to take risks, stretchers were installed in the body for rigidity (see photo 26, where the car looks quite naked) and this measure, I think, was not unnecessary - it’s better to be overdressed than underdressed.

The remains of the side members and jacks brought tears to my eyes... (photo 11, 12)

Having mercilessly chopped off pieces of old metal with a grinder and a chisel, we got to the living metal of the body. We welded in the amplifiers, connectors and front jacks. Buy a new book on auto repair from Khoma. We decided to wait a while before installing the doors to install the external sill panels in order to prevent the appearance of unnecessarily large gaps.

Finally, the turn came to the spars. This “hole” was what the sweet girl wanted to seal (photo 14)

The same photo shows that the edges of the wheel arches still have the same deplorable appearance. Removing the rear bumper and examining the trunk for integrity forced me to take up the camera again:

The left trunk well (see photo 21) and the rear panel (see photos 15, 32) also suffered from terrible rot. For further repairs, we had to remove the gas tank and the rear beam (photo 28). While they were filming, the soured brake pipes were told to live to death for a long time (see photo 23). There was no time to mourn for them, so the chisel, grinder and drill were used again. The edges of the arches were trimmed, the side members were drilled out, and the rear panel was cleaned down to bare metal. First, new spars were installed, and then new edges freshly cut from millimeter sheet metal were welded to them by spot welding, as well as parts of the rear panel (see photos 24, 25, 27, 16). At this point, the welding work was completed, but the owner expressed a desire , taking the opportunity to “make noise” of the interior, and treat it with anticorrosive... No sooner said than done, especially since the customer supplied the materials himself, with the exception of body iron.

So, the hidden cavities were treated with Movil, the interior was glued, the bottom was treated with bitumen mastic (the rear panel, of course, also got it) see photos 18, 19, 20.

Installation and operation of the tool

Step 1

First, we disassemble the engine compartment: drain the antifreeze, and then remove the radiator itself. The doors also need to be removed, if everything there is completely rotten, then you can simply tear it off, cut off the flanges with a grinder, to which the TV was welded.

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Step 5

In my case, the arches were completely rotten. Mechanics advise not to suffer or digest them, but simply buy and install new body elements. But if you are in the mood for repairs, then this is also quite possible. Spray resin is a good coating for arches, but even it will not save them in the future. Rust will get through it too. There are also other anticorrosive mixtures. The choice depends on the budget and experience with this or that material.

We hope this instruction will help you in repairing the body of your car and after the final stage - painting, it will shine like new.

Wings of the "nine"

The fixation of the front wings on the “nine” was done quite well, if we mean ease of removal. Just a few bolts hold them in place. Therefore, no welding is required to dismantle them; you just need to arm yourself with a pair of good shaped screwdrivers and an 8-size socket with an extension.

Remove the fender liners, which are held on by self-tapping screws;
The fender bolt holding the body element from below at the threshold is unscrewed;
Two more bolts hold the wing on the inside;
You will have to completely dismantle the bumper or unscrew its side fastenings, and then move it to the side to gain access to another bolt securing the wing;
Finally, it remains to remove a few bolts securing the wing from above.

It is also not customary to tinker with a wing if it is deformed. You can easily replace it with a new one, especially since it is inexpensive - 1200 rubles. If you use auto-disassembly, you can buy the part even at half the price.

If, however, the wing has received minor deformations or there are traces of rust on it, then it is easy to repair the part. Again, it can be removed and then finished to perfection on a garage workbench.

If you don’t want to remove the wing, you can repair it directly on the car using straightening hammers, pliers and a jack.

Painting

As a rule, after straightening work, painting of the wings is required:

First, the part is degreased and cleaned to a metallic shine;
Treat minor dents with putty mixed with fiberglass;
Finishing putty is applied and sanded well;
After drying, a primer is applied. Ideally, you should apply 2 layers and then paint;
Apply epoxy varnish in 1-1.5 layers on top.

You can read in detail about the repair and restoration of other body parts in other articles on our website. Video reviews and useful photos, diagrams and drawings will only be a plus.

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What the different modifications have in common

Checkpoints

Measuring the distances between body control points is the most common way to check the condition of a car. After taking measurements, you need to check them with the passport data.

The check is performed as follows:

Check Point

Passport sizes

Tolerance (+/-)

Diagonal of the front doorway from the edge of the lower threshold to the middle of the roof

Diagonal of the front door opening from the lowest point of the windshield to the middle of the lower threshold

Distance between front door hinges and pillar in a straight line

Diagonal of the rear door opening from the point where the lower sill joins the central door pillar to the roof

Diagonal of the rear door opening from the top of the B-pillar to the lower threshold

Long diagonal rear side window frame

Short diagonal rear side window frame

Distance from the middle of the windshield to the middle of the hood

The weakest link

The frame of VAZ 2109, 2108 cars has several weak points that are most susceptible to corrosion.

Rear beam mountings

The rear beam is attached to triangular brackets on both sides of the body with rubber-metal hinges. The brackets are secured with studs welded to the rear spar reinforcement. Foci of corrosion appear around the fasteners, destroying the thresholds, amplifier. If the damage is severe, the beam can be torn out of the body, which leads to loss of control. The bottom of the 2109 is repaired in the early stages of corrosion.

Fastening the brace brackets

The radiator frame in these places is reinforced with thick metal, which is subject to corrosion. The VAZ 2109 bottom repair insert is sold in specialized stores. The spare part is welded into place of the destroyed one, respecting the geometric dimensions of the body.

Suspension strut cups

Dirt accumulated in the wheel arches destroys mudguards and suspension cups. Cracks appear in the places where nuts and studs are attached due to high vibration load. Defects are eliminated by overcooking the glasses. For preventive purposes, it is recommended to use fender liners and renew the protective coating of the arches.

Thresholds

The most common problem with “nines”, which reduces body rigidity. Corrosion spreads under the plastic covers. It is impossible to change the thresholds without restoring the floor. Either the part is replaced completely, or the most damaged elements - amplifiers, lower part, outer lining.

Why do thresholds wear out?

Thresholds are load-bearing elements that provide the body with additional rigidity. Due to the fact that these parts are located in the lower part of the body, they are constantly exposed to negative factors:

All this significantly reduces the service life of the thresholds. In addition, the mediocre quality of painting and anti-corrosion treatment of body elements from the factory leads to the fact that almost every owner of a “Nine” is faced with the need to replace the thresholds on their car.

Signs of the need to replace thresholds on a VAZ 2109

The appearance of even small areas of corrosion on the thresholds is the first sign that these body elements need to be paid attention to.

At first glance, such areas may seem harmless, but if you examine them in more detail and clean them, it may turn out that under the layer of paint there is a serious source of corrosion or completely rotten metal.

It is important not to miss the moment when replacing the threshold is still possible. It often happens that the threshold rots around the perimeter and there is simply no need to weld a new part. In this case, more serious and labor-intensive body work will be required.

Threshold repair options

Repair of the body elements in question can be performed in two ways:

welding patches;
complete replacement of parts.

Tools

Body repair of a VAZ 2109, including replacing the bottom yourself, begins with the selection of tools. Restoration work requires specific equipment:

hammers of different sizes for straightening work;
grinder, set of discs for removing rust and paintwork;
carbon dioxide cylinder;
welding machine;
metal drills, chisels with a hardened tip;
two jacks, a lift;
metal brush;
standard set of tools - screwdrivers, wrenches.

Device

To understand the essence of repairing, disassembling and assembling a gearbox, first of all you need to get acquainted with its structure. In the case of the VAZ 2109, the box structure is as follows:

On the input shaft there is a block of drive gears that are in constant mesh with the driven gears of the gears when moving forward;
The second shaft has driven gears with needle bearings. There is also a pair of synchronizers located there;
The secondary shaft is created together with the drive gear of the main transmission;
The driven gear of the main gear is attached to the flange of the two-pinion differential box;
Differential bearings are always mounted with interference, which is adjusted by selecting rings of different thicknesses.

Checkpoint diagram

Where to start and where to end

Repair work begins with dismantling the deformed, rotten parts of the “nine”:

Disassembling the engine compartment, draining coolant and antifreeze.
Removing the doors.
Dismantling the amplifier - “TV”.
Rusty areas are cut off with a grinder.
The holes will have to be repaired or patched.
Problem areas are strengthened with iron.
Mudguards are reinforced with spot welding.
Spare parts are adjusted in accordance with the geometry of the car.
Thresholds and wings are fastened with bolts followed by electric welding.
New arches are installed, and if necessary, the bottom is completely changed.

To prevent the occurrence of corrosion, vulnerable areas are coated with special compounds based on bitumen, resin, and oil. The surface is pre-polished, removing a layer of paint and varnish, increasing adhesion to the applied product.

Welding materials

When working with a welding machine, consumables are required. When choosing them, they are guided by two points:

Thin steel is more difficult to weld and requires proper selection of temperature conditions.
Thick ones are more difficult to process.

In the lessons, experts advise using metal 1–2 mm thick for patches. The car is inspected on an overpass or pit in good lighting. The strength of the metal is checked with a hammer, which is used to tap the damaged areas.

How to replace the thresholds of a VAZ 2109 with your own hands

If a significant part of the thresholds is damaged by corrosion, then there are no options other than completely replacing these body elements. To carry out repair work you will need the following list of tools and materials:

semi-automatic welding machine;
new thresholds;
Bulgarian;
drill;
sandpaper;
putty and primer;
anti-corrosion compound (mastic).

Features of replacement and preparation for it

When planning body repairs, you need to understand that the design of the VAZ 2109 thresholds consists of the following elements:

outer box;
inner box;
amplifier

The outer and inner boxes are the outer walls of the threshold. The outer element goes outside and is located under the door, and the inner one is located in the cabin. The amplifier is an element located between two boxes inside. Most often, the outer frame is subject to corrosion, and when replacing thresholds, this particular body part is in mind.

Even though new parts are used when replacing thresholds, they still require preparation. From the factory they are covered with shipping primer, which must be cleaned before installation, i.e. the metal must shine. This is done using sandpaper or grinder attachments. After cleaning, the elements are degreased and coated with epoxy primer.

The final preparation of the thresholds comes down to drilling holes with a diameter of 5–7 mm for welding in the places where the parts adhere to the body.

Preparatory procedures also include the dismantling of doors, aluminum sill trims and interior elements (seats, floor covering, etc.). Before the immediate start of work on removing the old thresholds, a metal corner is welded to the racks from inside the cabin. It will provide rigidity to the body and prevent it from deforming after cutting off the thresholds.

Step-by-step replacement instructions

Having prepared everything you need, you can begin the repair. The procedure consists of the following steps:

Place the new threshold on top of the old one and outline it with a marker.

Video: replacing thresholds on a VAZ 2109

Damage to the sills by corrosion on the VAZ “Nine” is common. These body elements can be replaced by every car owner who knows how to use an angle grinder and semi-automatic welding. If you don’t have such experience, then it’s better to trust the specialists. Only in this case can one hope for high-quality repair work and a long service life of the thresholds.

Source: bumper.guru

Complete replacement

In case of severe damage from corrosion or metal obsolescence, the bottom of the “nine” is completely replaced. This requires:

To repair the “nine”, you can use one second of the bottom of the 2108 cabin.

Preparatory work

Before replacement, doors, fenders, and sills are dismantled. If there are traces of corrosion, the cover plate and connector are replaced. Installing braces for rigidity increases the accuracy of the work. Using a chisel, the old metal is removed down to the undamaged body. The internal surfaces of thresholds and cavities are treated with zinc chromate primer GF-073 before replacing the floor.

Along the lines connecting the threshold with the trim, holes with a diameter of 5 mm are drilled at a distance of 40–50 mm. The geometry is checked by installing doors in the openings, maintaining gaps of no more than 3 mm. The doors are then removed.

The threshold is welded to the trim with electric rivets through stitched holes, to the side of the body, to the central pillar - with a continuous seam. After completion of the work, the welding areas are cleaned with a grinding machine, primed, and coated with an anti-corrosion compound.

Useful tips

To repair the underbody of a car with your own hands, experts recommend using semi-automatic machines. The additive is supplied at a fixed speed, the burner provides uniform heating. The seam is of high quality and even. When working with electrodes, an inverter with additional functions that support constant operation is convenient. They reduce the risk of electrode sticking.

Before cutting a sheet of metal, the exact dimensions of the defect zone are determined. The patch must be suitable in size and adhere to the geometry. To deform, the sheet is not heated for a long time - the strength characteristics of the alloys decrease and they become friable. Movements of the hand with the holder or attachment should be uniform, without jerking. Large sections are connected with a continuous seam, leaving gaps of up to 3 cm. Such connections better withstand dynamic loads and increase the strength parameters of the body. Such connections require a durable insulating coating. Mastic prevents moisture from getting into microscopic gaps.

Protective fluxes are used to work with galvanized iron; they preserve the coating from boiling and burning. Knowing the intricacies of the process, making the connection is not difficult. The main thing is to take your time and carefully prepare the surfaces before work. Anti-corrosion work should not be neglected. The bottom is subjected to heavy chemical load during operation. Protective compounds are applied in an even layer.

Source: svarkaprosto.ru

Post-weld treatment

The first stage is polishing the bottom with coarse pastes with mechanical additives. Pastes without abrasive substances are applied after washing and drying the car. All work is carried out using a polishing wheel, which processes each part separately.

Primers

They cover clean surfaces of the car according to the instructions. The primer provides adhesion to anti-corrosion compounds. Manufacturers offer different formulations:

Tectyl is available in three types. Classic creates an organic microfilm on steel; zinc provides an additional coating that neutralizes salts; Tectyl HT zinc is intended for vehicles operating in urban environments.
Movil is an economical composition that is in demand in auto repair shops.
Bitumen mastic based on polymers, rubber, mineral shale.
Dinitrol based on polymer rubber.

After restoration of body parts, sound insulation must be installed. The bottom can be coated with Prim, which simultaneously acts as an anti-corrosion agent.

Corrosion protection

To protect the body from rust, two methods of anti-corrosion treatment are used.

ML oils

The method, invented in Scandinavia, involves pouring special oils into the technical cavities of the body through factory drains. The compositions impregnate the welding seams, covering the internal surfaces with a film, isolating them from contact with air. The bottom is coated on the outside with similar oils.

The inhibitors included in ML oils allow them to be applied over rust. They slow down the spread of corrosion, but for maximum effect, it is advisable to wash the body of the “nine”.

The disadvantage of the ML method is its low mechanical strength. Oils wear off quickly in open areas, but remain for years in closed spaces.

Bitumen compounds

Open bottom panels and wheel arches are coated with protective bitumen. The method places high demands on the preparatory work. External elements must be thoroughly washed, otherwise the bitumen composition will quickly be washed away.

The advantage of such coatings is their high mechanical strength. They protect the VAZ 2109 body from external influences for a long time. Bitumen compounds can be used as additional sound insulation: a film applied in several layers reduces the level of vibration of the panels.

Bitumen coatings can be applied to traces of corrosion, but with some reservations. Surface rust is pre-impregnated with ML oils, after which solid compounds are applied. For deep damage, this method will not help control the development of corrosion, since bitumen products, unlike ML compounds, are opaque. Because of this, when inspecting a car, the technician assesses the level of rust damage and decides whether to apply bitumen compounds on top.

Cylinder block

In any case, it needs to be repaired. First of all, clean the entire surface of oil, dirt and other deposits. The repair consists of boring the sleeves to the required size. You cannot carry out this procedure yourself; it is better to trust a specialist. The lathe who carries out the boring must have the skills to operate the machine. Do not trust such a task to an inexperienced person. Its reliability depends on how correctly the overhaul of the VAZ 2109 engine is done.

There are two boring options: under the mirror and with a fine mesh. In the second case, honing is done - the entire inner surface of the liners is covered with thin lines. Some people claim that this gives a boost in power. But in reality, the picture is the opposite - the wear of the piston rings increases, since the surface of the cylinder is similar to an ordinary file. Fortunately, this continues for 10-20 thousand km, after which the sleeve takes on a mirror-like appearance. Moreover, the geometry is not always ideal. For this reason, it is better to carry out boring under a mirror.

Self-repair of the bottom of a VAZ 21099

The lower part of the VAZ model 21099, as well as other cars, is more often subject to mechanical damage and the harmful effects of chemical reagents. Various means will help protect against corrosion, but it is unlikely to protect against damage. Bad roads will sooner or later make underbody repairs on the VAZ 21099 inevitable.

When a car service technician makes the diagnosis “the bottom needs to be overcooked,” the situation seems hopeless to the owner of the car, and the repairs are expensive. Of course, there are different cases, but they are not hopeless. For the most part, do-it-yourself bottom repairs are quite feasible.

How to properly weld the underbody of a car with your own hands

For a car with high mileage, corrosion of the bottom is a common thing. Mechanical damage, high humidity, and deicing agents destroy iron over time. The metal turns to dust. Driving such a car is dangerous, the car needs repairs. It is not profitable to contact a service station; the technicians may overcharge you. Having a welding machine, it is easy to weld the underbody of a car in the garage. It is important to take into account some nuances and adhere to technology. It is more convenient to carry out the work together; a partner will help fix the patch before tackling.

Ways to save

What often accounts for the high cost of service station services? It's rare to get by without tricks. Often the repair specialist inflates the price by simply exaggerating the labor-intensive and time-consuming repairs. To avoid this, the car owner can independently assess the condition of the bottom of the car.

To do this, you will need an overpass or inspection hole, powerful lighting and a hammer. Suspicious areas are tapped with a hammer, the extent of the rot is determined, from which the need for materials is approximately determined.

How to digest the bottom without the help of outsiders? Gas welding and semi-automatic welding equipment will be required. Using both types of welding improves the quality of repairs, and anyone can master the process and it won’t take much time.

Dismantling

To dismantle the box, we recommend that you rely on the instructions, strictly follow the sequence and reinforce your skills with visual videos.

Disconnect the negative terminal from the battery and drain the oil from the gearbox system.
Unscrew the bolts that hold the crankcase guard in place and remove it.
Disconnect the ground (wire) from the clutch housing.
At the end of the clutch cable, loosen the tension on the nuts slightly.
Remove the cable end from the clutch lever.
Disconnect the block from the traction relay.
Disconnect the wire going to the starter traction relay.
Dismantle the starter itself directly.
Disconnect the drive rod from the joint tip. We are talking about traction, which switches gears.
Disconnect the cable from the car's speedometer drive.
Unscrew the tie rod ball joint.
Remove and press the steering rod hinge pin out of the strut swing arm.
The shank of the inner CV joint of the front wheel drive should be pressed out and moved to the side.
Disconnect the second CV joint.
Remove the clutch housing shield.
Release the gearbox from the fasteners holding it to the engine.
Remove the box.

Carefully remove the gearbox
Be sure to move it horizontally away from the engine before directly removing the gearbox. Then disengage the input shaft. Be careful not to damage the clutch spring petals.

Required tools and materials

In addition to the listed welding machines for self-repair

the bottom of the car you will need:

Bulgarian;
metal scissors (electric or conventional);
hammers of different sizes and shapes;
good lighting quality;
consumables for welding (calcium carbide, oxygen);
copper wire;
carbon dioxide;
metal for patches;
consumables for grinding and cutting with a grinder;
primer, paint, anti-corrosion compound, rust converter.

When choosing metal to patch holes in the bottom, you should know that its thickness should be within 1-2 mm. Thin metal requires good quality consumables and debugging of equipment, because the temperature regime must be strictly observed.

Thick metal is more difficult to process, but it is also difficult to spoil.

Engine Condition Assessment

Let’s make a reservation right away that everything said below about how to make repairs applies equally to both carburetor and injection engines of the VAZ 21099 - apart from the power supply and spark generation systems, they have no fundamental differences.

Simply but effectively, the condition of the engine can be assessed by measuring the compression in the cylinders. A normal indicator would be a pressure of at least 10 kg/cm2. Lower values indicate wear of the piston group parts.

If there is a “failure” of pressure in one of the cylinders, while the rest are good, then pour 30-50 g of engine oil into the spark plug hole. If after this the compression increases sharply, then the piston rings are either broken or sunk. The absence of changes indicates burnout of the valves or breakage of their springs.

Skipping the engine removal procedure, let's move straight to how you can assess the condition of its parts and what measures should be taken to eliminate possible defects.

Application of metal patches

Welding the bottom begins with disconnecting the battery. The welding process will require the presence of an assistant. One fixes the patch, the other scalds it from below, carefully with a distance of several centimeters. If the patch is applied to a flat surface, it can be fixed using a semi-automatic welding machine.

The geometry of the body is constantly checked to avoid problems with doors not closing after repairs. The final seam is made continuous.

Bending the metal to weld the rotten bottom is done using gas welding. The softened metal quickly takes on the desired configuration. You can also use a special device for bending metal blanks. The seams on the surface are cleaned with a grinder and coated with anti-corrosion compounds.

When is it no longer possible to drive?

It is much worse when the bases of the roof pillars or the power structure of the sills, the cups of the struts or the side members in the engine compartment have completely rusted. All these places belong to the load-bearing elements of the body. If the rust has penetrated a third of the thickness of the metal, then driving such a car is already dangerous.

It's easy to spot serious problems. When driving over artificial bumps, the body flexes excessively under load. If you climb one wheel onto a stone or curb and stop, then the “rotten” body may have problems opening the doors or trunk. The body bends, deforms and pinches moving elements. There is nothing good about this anymore. In the event of an accident, such a body will not be able to resist the impact impulse and will collapse like a house of cards.

Metal cups also sometimes rust through. Their damage is indicated by knocking in the suspension and noticeable problems with handling.

It is no longer possible to drive with such damage due to the risk of a serious accident. It is impossible to fix them, although some garage mechanics, of course, weld patches onto the side members or try to restore lost suspension fastenings, but it is no longer possible to restore the body’s former strength.