Repairing car sills with your own hands without welding from below

Cold methods of sealing holes in thresholds

Depending on the degree of damage, a cold or hot repair method is selected. The cold method includes body work that does not require welding equipment. A small hole can be sealed:

construction putty;
using fiberglass;
primer and secured with moldings.

The semi-hot method involves using a soldering iron to seal small holes.

How to fill a hole with fiberglass

The easiest way to repair a hole in a car sill without welding is to use a fiberglass patch. For repair you will need:

The two fiberglass patches are 2cm larger than the corrosion area. Fiberglass or fiberglass can be used.
Automotive primer, degreaser.
Sandpaper, grinder for preliminary cleaning of the surface.
Putty knife.
Varnish, paint.

Self-repair takes up to 1 hour and does not require special skills, you need:

Use a grinder to remove the old paint layer.
Clean the threshold, if rusty dents or through holes are found, treat with a degreaser.
The dents should be primed well and the material should dry completely.
Cut out the fiberglass pads, place them on a dry surface, and secure them with adhesive and epoxy resin.
After drying, the surface is primed, sanded and painted.

When using fiberglass, it is recommended to additionally secure the thresholds with moldings.

Filling holes with putty

It is recommended to restore thresholds with putty in the following cases:

In the absence of large through holes.
If moderate pockets of corrosion are observed that have not affected the geometry.
For primary rust.

Sealing thresholds using this method is quite simple; repairs take up to 2 hours and do not require special skills, but you must have the necessary tools and material. For repair you will need:

construction fiberglass and automotive standard putty;
Bulgarian;
aluminum mesh if you have to patch a significant but only hole;
medium abrasive sandpaper from 800 grit;
medium spatula;
degreaser;
automotive primer;
paint, varnish.

Starting repairs requires preliminary preparation of the surface, for this you need:

Clean the threshold from old paint by cutting off the layer of waste material with a grinder.
Sand the surface and treat with degreaser.
If the threshold does not have through holes, aluminum mesh is not used. If a significant deep focus of corrosion is discovered, cut out a patch of the required size from the mesh and apply it to the recess.
Cover the mesh with construction putty. If the damage is minor, apply a layer of putty, leveling the composition. Let it dry.
Sand and apply a thin layer of automotive primer.
After drying, clean the area with sandpaper.
Paint over, varnish.

The option of sealing holes with construction putty is often used when repairing a body, but experienced drivers do not recommend it, since it begins to dry out after 7-9 months, allows moisture to pass through, and corrosive destruction continues.

Cold welding method

The method is suitable for sealing small holes in thresholds, when there are no large pockets of rust and the internal metal, threshold amplifier, is not damaged. For repairs you will need polyester resins for body work, i.e. epoxy. Repair process step by step:

Holes are cleaned with emery, a grinding wheel, and degreased.
The resin is diluted in the required proportions or a ready-made composition is used.
Fiberglass of the required size is impregnated with resin and glued to the hole.
After drying, the surface is primed, sanded and painted.

This method is suitable for repairing those parts of the body that do not experience stress. If this method is chosen for thresholds, it is recommended to always install metal moldings.

Common Mistakes

If you have no experience in body repair, you can make mistakes even when correcting minor damage. To prevent them, it is useful to familiarize yourself with the mistakes that beginners and non-professionals make most often.

Common mistakes when repairing thresholds:

When repairing metal thresholds, the surface is not cleaned properly. The entire outer part and connector must be carefully treated to remove all traces of rust.
Metal patches welded to thresholds are not treated with anti-corrosion compounds. To prevent the metal from becoming leaky, it must be cleaned and an anti-corrosion compound applied on top. They also need to process the insides of removable thresholds.
I don't treat the underbody of the car. When repairing, it is necessary to apply protective mastic to it.
They forget to check the drainage holes. They need to be cleaned and Movil or another preservative must be poured into the cavity of the thresholds.

Every car enthusiast will be able to eliminate minor defects in thresholds, having the necessary tools and materials at hand. If everything is done correctly, you can postpone contacting the service for a couple of years. Complex damage requires the use of welding and certain skills, and if they are not available, it is better to turn to professionals.

Repair by sealing the hole with metal

Metal patches and subsequent soldering are considered the most productive means for restoring thresholds, even with a large area of corrosion. If rust has not led to deformation of the central pillars and distortion of the geometry, then you can use metal patches and strengthen them with a soldering iron. For repairs you will need the following materials and tools:

metal patch, size 2 cm larger than the corrosion hole.
assembly hammer;
Bulgarian;
medium abrasive sandpaper;
anti-gravel;
anti-rust composition - phosphoric acid, if available;
soldering iron, tin solder;
automotive primer, degreaser.

Fixing pinholes

When diagnosing a car, if there is a pinhole from corrosion on the threshold, in 80% of cases it is necessary not only to repair the hole, but also to change the amplifier. A full inspection will reveal large areas of rusty metal under a layer of paintwork. If a pinhole occurs from mechanical damage, then it is not associated with natural wear of the metal, so small holes are sealed using putty or soldering.

Soldering is carried out according to the same algorithm as sealing a hole with a sheet of metal, the only exceptions being the small size of the patch.

Use of soldering

If small holes in the threshold or bottom of the car are sealed with soldering, then simple tips will help:

For heating metal more than 0.5 mm thick, household soldering irons are of little use. It is better to use a portable gas burner that has a small cylinder from 400 to 700 ml. The work will go faster.
To solder thresholds you need solder and flux. For solder, a composition with lead or tin is used; the flux can be replaced with electrolytic acid.

Experts recommend not using soldering for body work at all. The main reason is that solder, tin or lead have a much lower electrical potential than iron; during their contact, electrochemical corrosion occurs, which can subsequently lead to full-fledged rust at the joints.

The second disadvantage of soldering is hot work, which is carried out in a safe place and as carefully as possible.

Replacement process

Let's look at how to replace thresholds on a VAZ with your own hands. Before cutting or welding anything, you need to remove all the doors, and then pull out the threshold; it is located under the door seals. Now you need to remove the seals to make it easier to work with the thresholds, and also leave the rubber bands intact.

Next you need to cut off the rotten parts of the thresholds, but this should be done starting from the places at the front doors, then at the rear, and only at the very end in the center. This is done so as not to damage the central pillar.

We remove all rotten places using a grinder or a thin drill; the back of the threshold must be drilled out in places of reinforcement. They drill out the front in the place where the old connector will remain.

We remove the threshold amplifier, but do not forget to leave part of the old amplifier so that metal can be welded to it. When we have removed all parts of the threshold that were subject to corrosion, it is necessary to clean the rusty areas.

Now you need to weld the purlin, on the subframe reinforcement, you need to overlap the connector; if it’s easier, then weld the joint into the joint with the old one.

We level the threshold, adjust it to size and protect the places for welding seams. Using a drill, we will make holes for welding on the bottom of the panel. Then this part must be welded to the bottom, along with the connector. Finally, the metal is welded on the side of the upper part of the threshold, and patches are placed at the bottom.

In addition to everything, it is necessary to remove the welds, putty and paint, making sure it is tight. Replacing thresholds on classics is carried out in exactly the same way.

Repairing large-scale damage

Any hole in the threshold of a car indicates the beginning of corrosion, but what to do if the destruction of the metal is large-scale and simple means cannot be avoided? In this case, a gas welding machine is required, a complete digestion of the body, and sometimes a complete replacement of parts of the bottom and wings.

Superficial repairs using putty, fiberglass, and small metal patches will not change the situation dramatically; rotting of the body will continue.

Thresholds and bumpers are considered the most vulnerable parts of a car body. Gravel flying out from under the wheels of the vehicle in front damages the paintwork, and improper crossing of the edge and careless parking lead to dents. Timely repair of thresholds without welding with your own hands will prevent corrosion of the metal and seal and restore the aesthetics of the car.

Purpose and types of auto thresholds

To repair car sills, you need to thoroughly study their design. This part of the machine is a hollow closed structure consisting of several elements.

Components of an auto-threshold:

inner part;
outer part;
between them is an amplifier;
the bottom bar is a connector (protects the cavity limited by the amplifier and the inside of the threshold).

Functions:

protection of the car from scratches, deformation, mechanical damage;
simplify entry (exit) into the salon;
decorative addition.

Repair of car thresholds depends on their design and material. All auto thresholds are divided into two groups according to their design:

Removable. They are an element of the body, but do not experience force load. The parts are attached to the bottom of the car using bolts. They are screwed on from the inside - in the cabin. In 90% of cases, the removable element is replaced rather than repaired. If desired, it can be repaired, and this can be done more easily than in the case of a fixed structure. The element is removed, repaired and put back in place.
Fixed. They, being part of the underbody of the car, simultaneously serve as a protective and decorative element. They experience a certain force load, increase body rigidity and affect the safe operation of the car. Consist of a seal and an outer surface. Non-removable sills are welded to the body. Therefore, repairing car thresholds in this case is much more difficult. It is easier to repair a non-removable threshold without replacing it - it can be straightened, puttied, holes filled, etc. But in case of replacement, you will need a more professional repair and definitely a welding machine.

On a note!
The outer panel of the car is made of metal or plastic. Metal thresholds are either removable or non-removable, while plastic thresholds are only removable.

What are the defects?

Depending on the degree and type of damage, the repair method is selected. Without welding, it is possible to restore a part in the following cases:

Dent of a non-removable element, bend of the lower edge. If the dent is shallow and without a sharp edge, then the drawing method, back hammering, and straightening are used.
A chip in the paintwork with a small area of corrosion. Anti-corrosion metal treatment, stripping, and grinding are used.
Point-through corrosion can be repaired with epoxy resins and fiberglass patches.

Do-it-yourself repair of rotten thresholds is carried out only by welding. It is necessary to cut out or knock out the rusted metal, weld a patch or a new part of the structure.

Removable elements are repaired only with minimal damage: dents, scratches, chipped paintwork. In case of serious defects, the part is replaced with a new one; the cost of the analog and repair costs are almost the same.

Restoration methods

There are more than ten ways to repair car thresholds with your own hands without welding. With the advent of new samples of glue, resins, protective fibers and equipment, the number of methods is increasing. The most common, simple ones for garage repairs:

fiberglass treatment;
epoxy glue;
construction foam;
hood without painting;

The use of a reverse hammer, as well as a spotter, are both spot welding repair methods.

fiberglass

Repair using fiberglass or fiberglass is quite simple, cheap, but reliable. Advantages:

does not interact with reagents on the roads - water, acids, electrolyte;
has little weight;
easy to use;
used for a long time;
has a low price.

As an alternative, fiberglass or fiberglass is used. The method is used if there are pronounced pockets of corrosion on the metal, without impact deformation. Epoxy glue or resin is used together with the material.

For repairs you will need sandpaper, hardener, brushes, spatulas of different sizes. As a substitute for epoxy glue, you can use polyester resin, which is similar in properties, but somewhat inferior to epoxy in strength. To complete the surface sealing you need:

Use a grinder to remove the paint layer.
Sand it with sandpaper.
Cut a patch from the fiberglass larger than the corrosion area.
Degrease and prime the surface.
Glue the patch with putty or epoxy glue.
Fill the surface and prime it.
Treat with anti-gravel compound.
Paint it.

Epoxy glue

A common epoxy adhesive is the ED-20 brand; as a rule, it comes complete with PEPA hardener. These components are mixed in a ratio of 1:10. When working with epoxy glue, you must take precautions, protect your eyes and hands. Contact with chemically active substances can cause severe irritation of the skin and mucous surfaces of the eyes, which can cause allergies.

The repair procedure is similar to using fiberglass. If the deformation is minor, it is permissible not to use reinforced mesh. The glue is applied to the damaged area in several layers, puttyed, primed and painted.

Construction foam

Manufacturers of Japanese vehicles often use special foam, which is used to fill the permanent threshold box during factory assembly of the car. It is believed that the material will ensure that there is no corrosion inside the threshold and will preserve the parameters of the seal. The sealant is anti-corrosion resins and mastics, polyester components, which have nothing in common with construction foam.

How to stretch a threshold without welding

Repairing a threshold after a dent involves using a reverse hammer, a suction cup, or cutting the area of deformation for a non-removable element. The algorithm of action is as follows: it is necessary to drill holes with a diameter of 1-2 mm near the dent, insert special metal corner hooks of a reverse hammer into them. Then tapping on yourself straightens the area of deformation.

You can weld by spot welding, placing the end of a hammer on the dent, and drawing out the metal. In this case, you need to start from the corner of the dent, welding the end every 3-5 mm, while straightening the surface with a hammer.

The most reliable way to stretch the threshold without full welding is to use a spotter, rings, or stop. The method is often used at service stations, since many drivers do not have the necessary tools in the garage. You can make the device yourself from a used microwave oven. Drawing process step by step:

The negative terminal from the battery is disconnected.
Using a sanding machine, a layer of old paint is removed from the entire surface of the dent.
Spot welding is used to install rings through which the puller bar is passed, and the metal is drawn out using a stop. The procedure is repeated until the surface becomes as smooth as possible.
The metal is sanded with emery, treated with a degreaser, and primed.
A thin layer of automotive putty is applied and treated with anticorrosive.
After complete drying, it is painted with enamel.

Another way is to use a vacuum suction cup. This approach allows you to preserve the paintwork. The difficulty of using suction cups is due to the uneven edge of the dent; it is quite difficult to use a vacuum even if the dent has sharp edges and metal creases.

A frequent question about how to repair rotten sills on a car has only one answer: nothing. Rotten parts must be knocked out or cut out, the seal checked, and new metal welded. Cosmetic repairs are used only before urgently selling a car, but this is just one way of deceiving a gullible driver; it has nothing to do with a full restoration.

It must be remembered that thresholds are called rotten if metal corrosion exceeds 65-70% and there are through holes.

With minimal foci of primary corrosion, the elements are ground, treated with putty, and primed. To strengthen the structure, plastic or aluminum overlays are used.

Final stage

Regardless of how the car body was repaired, they all end with putty. However, it absorbs moisture, which leads to rapid destruction. Therefore, it must be coated on top with an anti-corrosion or epoxy primer. Body repairs are completed without welding by painting. To do this, use a spray gun or aerosol cans, after covering the adjacent surface of the car with plastic film. You should not use a brush, as drips are possible.

The proposed methods will help to repair a car without welding in case of single damage. However, if a large area is affected by corrosion, it will be easier and more reliable to contact a car repair shop to replace the rusted area by welding. Most often this happens to the floor, so it is recommended to regularly check it from underneath the car using an inspection hole or lift.

A source of through corrosion, or simply a hole, in the bottom of the car is the price to pay for comfort in the cabin. Its primary source is not anti-icing reagents acting outside, but moisture accumulating under the “pie” of heat, sound and waterproofing. Therefore, when eliminating it, work is carried out mainly from the inside.

If you follow all safety rules when welding, you must completely dismantle the interior, including the trim. This is always very time consuming. Therefore, the question of how to seal the bottom of a car without welding is very relevant. Moreover, most alternative methods do not give worse, but rather better results.

Restoration of permanent thresholds

A reliable technology for restoring a permanent threshold remains the application of a metal patch by welding if there are through holes and large corrosion damage. Pull out dents with a reverse hammer or spot welding; chipped paintwork with epoxy resin.

If it is necessary to repair a removable part from primary rust and it is not possible to replace the part, it is recommended to use fiberglass and epoxy glue.

The thresholds are first removed so as not to damage other body parts. Then traces of rust are removed from the surface using a solution. Next, the epoxy resin is diluted with a hardener and applied to a previously degreased surface. Pieces of fiberglass of the required size are placed on the laid glue and pressed down for adhesion. After 12 hours, the area is sanded, uneven areas are removed, a layer of primer is applied, and at the final stage it is painted.

If we are talking about minor damage - rust or dents in a small area, then even beginners can do such repairs. If you lack the skills or desire, it is recommended to contact specialized workshops; tinsmiths will conduct a full inspection of the part and adjacent elements, and will also suggest how to seal the thresholds in the car reliably and quickly.

Body repair without welding using aluminum mesh and fiberglass putty

In this situation, there is such a rusty hole that needs to be removed, or sealed, in short, do everything to ensure that it does not exist.

1. Using a grinder or other convenient device, remove the rust.

2. Next, we take the patch and “fit it out” in place to understand how it will fit.

3. Using masking tape, attach the patch to the body.

4. Next, take fiberglass putty and apply it in a thin layer so as not to touch the tape; we will remove it later.

5. When the putty has stuck, remove the tape and continue filling the surface with the same putty.

6. We try to apply the putty in a thin, even layer, avoiding bumps. Also, if possible, we try not to increase the working repair surface, although if this does happen, then the situation can be corrected using sandpaper or a sander.

7. After the putty has dried, take a coarse-grain sandpaper (in my case it’s “120” number) and start sanding. If you have a grinder on your farm, we use it, it’s faster and more convenient.

8. After the surface is brought to a “flat and smooth” state, we proceed to the second stage - filling using automotive putty.

9. Next, we level everything again with sandpaper and prepare the surface for priming. In the photo below you can see approximately what the surface should look like when prepared for priming.

10. Next, in principle, everything is the same as everyone else’s, pour the primer into the spray gun, wrap the unpainted parts and surfaces with oilcloth, and then proceed to the primer.

11. After the surface is primed, you can begin painting.

12. On the back side of the surface to be repaired, it is also necessary to apply several layers of putty to strengthen the aluminum mesh.