Replacing the threshold is not an easy job for a craftsman and not a cheap pleasure for a car enthusiast. Some I had to hear from my clients "Can you somehow do without a replacement?", And there really is a way out, repair of the threshold with fiberglass.
The lower part of the threshold has large metal corrosion centers. It is not possible to repair using welding and patches, we will glue it from fiberglass.
Using a metal drill bit, we clean the area of corrosion and an area of 5-10 cm. Around.
At this stage, it is necessary to process the corrosion center, this is necessary for better adhesion of materials. We will use a well-known tool called "Rust converter" ... It is quite easy to use, you just have to follow the instructions on the product.
To fill the void, you can use various means such as: plasticine, cardboard, polystyrene, wood, etc. In this case, the most optimal and convenient to use is polyurethane foam. Under its weight, the foam tends to "fall off", so you need to prepare in advance for this unpleasant moment. To do this, you need to prepare a stand, all the various tools at hand will do. In my case, it is a wooden board. To facilitate further work, I advise you to cover the stand, for example, with newspapers or film, since it will be quite difficult to separate the foam adhering to the tree.
Before starting to fill the cavities with foam, lightly dampen the surface with a regular garden sprayer. This is necessary for better adhesion to the metal.
Using a knife, we cut off the foam and create the most approximate shape of the threshold. For a more accurate removal of the plane, the foam can be leveled with a bar with P40-60 sandpaper.
Working with fiberglass requires some knowledge and a lot of patience. Before starting work with composite materials, it is necessary to protect the body from accidental ingress of resin drops. To do this, I advise you to cover the body with paper or film. The repair surface must be well cleaned and degreased. We dilute the polyester resin in the required amount. Polyester resin is diluted in a ratio of not more than 2% of the catalyst by volume of the resin. Using a brush, saturate the entire surface with resin, then apply glass mat with a density of 300gr / m2. For ease of use, it can be divided into two parts and we get the 150th. This is necessary so that the glass mat does not fall from its weight from the lower part of the threshold, so the build-up of layers should be done gradually, after each layer has dried. Two layers of 300 glass mat will be enough. To insure against "sliding" of all this mass, make some kind of support under the lower part of the threshold.When the resin is dry, the resulting fiberglass must be prepared for the application of the putty. Grinding with coarse abrasive P40-60.
Absolutely any putty on fiberglass can be applied. If a thicker layer is required to level the surface, then it is better to use a filler with fiberglass, then universal or with an aluminum filler. After leveling the surface, it is necessary to prime it, apply an anti-gravel coating on top of the soil and paint.
The thresholds of the car, like any external parts of the body, over time acquire a certain amount of damage associated with the operation of the car. Many drivers suffer the fate of repairing this unit, especially if they own a car with significant mileage and already a decent service life. Carrying out repair work with your own hands is a very real task if you have the skills and simple tools, in some cases - welding.
The main types of damage to thresholds (regardless of the type of such elements) include:
VIDEO Depending on the nature of the damage, restoration is resorted to in different ways:
To fix small dents, repair of car sills for removable elements, it is necessary to dismantle this part from its regular place (most often it is fastened with simple self-tapping screws).After that, place it on a plane convenient for work and use a mallet to straighten the damaged areas. Then, when the paintwork peels off (this often happens if you do not calculate the impact force), paint the damaged area with your own hands or apply paint to the entire part. Also, when repairing a metal part with your own hands, it is necessary to apply an anti-corrosion compound to the treated area.
If the removable thresholds are mostly damaged by rust (holes are through), the best option would be to replace them.
If the threshold is non-removable (in most cases), do-it-yourself repairs will have to be carried out from the outside. In the presence of minor damage, dents can be removed using a special tool (vacuum inverter). A small-diameter hole is drilled in a certain part of the product, then an inverter is inserted into the hole and under the influence of high pressure the dent is straightened.
The situation is more difficult if the threshold is severely damaged by rust. In this condition, it is necessary to perform a complete cleaning of the surface (using sandpaper, cleaning is carried out, then the surface is degreased and painted).
It is rather difficult to carry out this procedure with your own hands, it is advisable to have one assistant.
In the most advanced cases, welding can be used. However, the use of welding occurs only when it is almost impossible to replace a part or repair it with your own hands. There are many welding methods on the market.
If there is a desire, a certain tool and sufficient time, the repair of car thresholds becomes quite possible. Correct application of the acquired knowledge guarantees a successful result.
Repair of the threshold is complicated by the fact that access to the reverse side of the damage is closed. In addition, the metal of the threshold, by virtue of its design, has a high rigidity and a significant effort is required to straighten it.
In this article, we'll look at several ways to repair the damage at the doorstep. Professional repair of significant damage will require specialized equipment. If the dent is small, then you can do with improvised means.
In modern body repair, when straightening deformed thresholds, a spotter and various pulling devices are used (for more details on these devices, see the article "Spotter"). First, the protective coating is peeled off from the threshold to pure metal. Then, with the help of a spotter, the pulling elements are welded to the threshold, after which the dents are gradually pulled out and the protruding places and folds around the deformation are simultaneously tapped, if necessary.
The pulling sequence is carried out depending on the structure of the damage. If the sill flange is damaged (the lowest part where the sill is connected to the bottom), then it must be returned to its place first. Next, you need to straighten the corners of the threshold if they are jammed. Thus, first you need to return the basic shape of the threshold, and minor irregularities are straightened out last. Shallow dents can be corrected with the reverse hammer included with the spotter.
If there is no spotter, but there is a semiautomatic welding machine, then a reverse hammer can also be used to straighten the threshold (which can be purchased separately or made by yourself). The principle of its operation and a simplified diagram are described in the article "How to straighten a dent with your own hands."
The next method does not require pulling devices.You can cut the dent with a cross (as shown in the photos below) and put each of the segments of the dent in place, for example, using a screwdriver. Next, you need to weld all the cuts.
A smooth, wrinkle-free dent can be straightened with a pulling device and hot glue. A similar principle is used in the PDR paintless dent repair adhesive system. The pulling device can be made by yourself from wooden blocks and a long bolt with a nut and washers (see photo). The block with the bolt is glued to the deepest part of the dent, after which the bolt gradually twists and pulls the glued block along with it.
The bars that will rest against the whole part of the threshold (on both sides of the dent) must be made large enough in area so that the force dissipates and the whole part of the threshold does not deform. It is better to make the block that will be glued from durable wood so that it does not crack or delaminate during pulling. You can use birch. The head of the bolt, which will be on the glued side of the bar, must be sunk by drilling a hole of the required diameter. This will keep the bolt out of the way and will not rotate while the dent is being repaired.
To apply hot glue, you can use either a special gun or a construction hairdryer. A hair dryer can also be used to warm up the glue if it hardens during application over a large area of the bar. Before gluing the bar, the threshold must be thoroughly cleaned, dried and degreased. Pull out slowly, pausing after tightening the bolt several times. If the glue comes off ahead of time, before fully stretching, then it may be necessary to re-glue and repeat the pulling several times. You can gently tap the bumps around the indentation while pulling (if any).
On convex body panels, when the dent is formed, the metal not only goes inward, but also forms bumps around the recess, which must be gently tapped when straightening the panel, helping the metal to return to its place. In the illustration, the large arrow shows the direction of impact, the small arrows indicate the raised metal around the groove (shown in dotted lines).
You can gently pry with a spatula and use isopropyl alcohol to remove any residual cured glue.
In this way, any damaged threshold cannot be straightened, but it is quite possible to reduce or completely straighten a smooth dent formed by a moderate impact. Once again, I repeat that one time it may not be possible to reduce the dent. You need to monitor the changes and if the dent has decreased slightly, then you need to slowly repeat the pulling process.
Sooner or later, many motorists have to resort to repairing car thresholds, especially those who have not new cars on the maintenance.
The quality of Russian roads is still not ideal, and when it will be so, the question is rhetorical.
A huge number of pits can render the car unusable, and after a few years seriously shake the nerves of the owner.
At the same time, the thresholds of the car, the bottom of the doors and the arches suffer most from such extreme driving.
Naturally, even the first signs of corrosion cannot be triggered and action must be taken immediately. If there is no desire to do the repair of thresholds with your own hands, then it is better to contact a specialist.
Today, there are two main types of thresholds - welded to the base or removable.
Removable sills are attached to the side and outside of the side members. Their main purpose is to protect the lower part of the car from small stones flying out from under the wheels.
Welded thresholds are more common. In fact, they merge with the underbody, giving it an extra level of rigidity.
Most often, removable thresholds are made of metal (less often of plastic). Fastening is carried out using self-tapping screws.
It is very easy to repair them. It is necessary to carefully remove the product by unscrewing the screws and restore the threshold with a small hammer (if we are talking about a metal product).
After that, the threshold must be covered with a special anti-corrosion compound to prevent the appearance of rust.
There are situations when the repair of removable thresholds is useless (for example, when the material has already completely rotted).
It is better to completely replace the old threshold with a new one. This will ultimately come out much cheaper.
Such a threshold is part of the structure, therefore, the repair must be carried out according to a different scenario.
If the damage is minor, straightening is done from the outside. If there are small dents, it is necessary to drill a small hole in the threshold and straighten the problem area using special tools.
Tool for pulling out dents.
Another option is to carefully cover the damaged area with small steel patches. Any competent tinsmith can easily cope with such work.
Dents in thresholds can be repaired with a steel bar that is welded to the damaged part and then pulled out using hand force or a special winch. Once the work is complete, the rod can be cut off.
In case of moderate damage, the seats and doors will have to be removed. Otherwise, the latter will interfere with the performance of high-quality repairs.
Areas with the largest damage should be replaced. These include:
Through holes;
Deep dents;
Torn off parts and so on.
This area can be cut out with a grinder and welded on a metal structure of appropriate dimensions.
Today, there are two main methods of straightening car thresholds.
In the first method, a rectangular window is cut into which the anvil is inserted.
This method allows the affected area to be tightened using hydraulic or mechanical devices.
Once the problem spot is fixed, the cut window can be welded neatly. Tin solder can be used to straighten the seam.
In the second method, the so-called transverse cuts are used, which are made in the surface of the threshold.
The weld points are disconnected, an anvil is inserted (preferably small) and the damaged area is straightened.
Welding is carried out only after straightening the surface. If the area directly under the door is damaged, then it must be cut out and replaced with a similar one.
If the rack is also damaged with the threshold, then it is necessary to simultaneously replace the threshold and the rack. It is necessary to act according to a simple scheme.
First, the B-pillar spar must be cut. Before you start straightening the spar, you need to make sure that the car body is strong.
After that, the installation site should be cleaned, and all excess metal parts removed.
Further, the surface of the side member must be leveled and adjusted. After that, fastening, installation and welding are performed. That's all. It remains to put the doors in place and adjust the gaps.
There are two main processing methods.
The first method involves the use of auto chemistry (mastic, special varnish or impregnation).
This method is most effective when working in a garage. But there are also negative aspects - the purchase of expensive materials is required to carry out the work.
In some cases, you can use cheap products, but they are not suitable for all foreign cars.
The second way is electrochemical protection. This treatment must be carried out exclusively by an automotive workshop where you can expect to receive a warranty.
The peculiarity of this protection lies in the fact that special electrodes are mounted on the threshold, to which a direct current is supplied.
These products pull corrosion on themselves, and not on thresholds. The term of such protection is about one year. As for the cold season, the electrodes will last a much shorter period - about three months.
In some services, ordinary plastic door sills are installed, which have a more affordable price and are easy to change.
These pads reliably protect the thresholds from dirt and stones, but do not protect against corrosion, which "gets" under them.
Therefore, if you really put such a pad, then only after anti-corrosion treatment.
Video (click to play).
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