Car sills are one of the most vulnerable parts of the body. Corrosion, mechanical damage after an accident or unsuccessful parking, deformation from hitting a curb - all this requires surgical intervention. Many car owners are afraid to take on the task of repairing thresholds with their own hands, for fear of aggravating the problem or ruining the geometry of the body. However, with the right approach, the necessary tools and patience You can pull out the threshold yourself, saving on car service costs.
In this article we will analyze the entire process from A to Z: from diagnosing damage to final anti-corrosion treatment. We will pay special attention safety precautions, the choice of tools and typical mistakes that beginners make. You will also find unique recommendations for working with aluminum thresholds of modern cars, which require a different approach than steel parts of classic models.
1. Diagnosis of damage: when pulling is possible and when not
Before starting repairs, it is necessary to assess the extent of damage to the threshold. Not all deformations can be pulled out - in some cases, the only way out is to completely replace the element or part of it.
There are three evaluation criteria:
- 🔍 Depth of the dent. If the deformation does not exceed 3–5 cm and the metal is not torn, pulling is possible. Deep dents (more than 7 cm) with sharp edges often lead to cracking of the metal when trying to correct the geometry.
- 🛠️ Condition of the metal. Rust, through holes or severe thinning of the material (especially on old cars) make pulling pointless - the threshold will simply tear.
- 📏 Body geometry. If the deformation affects load-bearing elements (such as side members), self-stretching may violate factory parameters, which will affect safety.
For an accurate diagnosis, use ruler-template or laser level, to compare the geometry of the damaged threshold with the undamaged area. Also inspect the dent from the inside (by removing the door trim or plastic sill trim) - often hidden cracks or corrosion are visible there.
⚠️ Attention: If the sill is deformed as a result of a severe impact (for example, after a head-on collision), do not attempt to pull it out without first checking for wheel alignment stand. Violation of body geometry can lead to uneven tire wear and poor handling.
2. Tools and materials: what you need for work
The success of a repair depends 50% on the right tools. Unlike professional workshops, where they use hydraulic stands and laser meters, at home you can get by with a more affordable set. Below is the minimum kit for pulling out the threshold:
| Category | Tool/material | What is it for? | Alternative |
|---|---|---|---|
| Basic Tools | Reverse hammer (with grip set) | Pulling out dents without damaging paintwork | Homemade hammer from a hairpin and a weight |
| Straightening | Set of straightening spoons (flat, curved) | Aligning metal from the inside | Wooden block wrapped in fabric |
| Fastening | Clamps (3–5 pcs.) | Fixing the threshold when pulling | Heavy vice or assistant |
| Protection | Soft pads (rubber, felt) | Preventing scratches when using a hammer | Old towel or foam rubber |
| Control | Magnetic square or ruler template | Checking geometry after repair | Smartphone with application level |
Additionally you may need:
- 🔧 Bulgarian with a cutting wheel (if you need to remove rust or cut off welding seams).
- 🔥 Welding machine (for welding repair patches or attaching back hammer grips).
- 🧴 Anti-corrosion compounds (Movil, Dinitrol, Body 930) for final processing.
- 🎨 Auto enamel and varnish (if painting is planned after repair).
If you don't have a back hammer, you can make one from an old jack by welding a hook or grips to the rod. The main thing is to ensure smooth movement and reliable fixation.
3. Vehicle preparation: dismantling and protection
Before starting work, the car must be properly prepared. This will not only make access to the threshold easier, but will also protect other body elements from accidental damage.
Step 1. Washing and cleaning. Wash the threshold and surrounding areas thoroughly with car shampoo and brushes. Remove dirt from all crevices and joints. Pay special attention to the inside of the threshold - sand and salt often accumulate there, which accelerate corrosion.
Step 2. Dismantling the casing and linings. Remove the plastic door sill trims (they are usually attached with clips or screws) and the door trim. In some models (for example, Volkswagen Passat B6 or Toyota Camry) to access the inside of the threshold you will have to remove the seat or part of the floor.
Step 3. Paintwork protection. Tape adjacent body panels masking tape and covering film. If you weld, use asbestos sheet for protecting glass and plastic parts.
Remove the negative terminal of the battery|Wash and degrease the threshold|Remove the plastic covers|Protect adjacent panels with tape|Check access to the inside of the threshold-->
Step 4. Assess internal damage. Inspect the inside of the threshold for hidden cracks or rust. If through holes are found, they must be brew or pay before pulling. For temporary fixation you can use epoxy resin with reinforcing mesh.
⚠️ Attention: On vehicles with aluminum thresholds (for example, Audi A6 C7 or Jaguar XF) it is strictly forbidden to use metal heating with a torch - this leads to a loss of strength. For such models, use only cold straightening with a reverse hammer.
4. Threshold pulling technology: step-by-step instructions
The pulling process depends on the type of damage, but the general scheme of work looks like this:
Stage 1. Marking and fixing. Apply to the threshold chalk marks, indicating the boundaries of the dent. Secure the car to lift or overpassto ensure sustainability. If you work on the ground, use safety stops under the wheels.
Stage 2. Selecting the point of application of force. For the reverse hammer, choose a location that has the least amount of deformation but is strong enough to attach the claws. On steel thresholds, you can weld temporary “ears” (pieces of metal with a hole) to which the hammer will cling.
Stage 3. Gradual stretching. Start from the edges of the dent, smoothly moving towards the center. Don't use excessive force—the metal should "flow" and not tear. After each jerk with a hammer, check the geometry ruler-template.
For deep dents use "step pull" technique:
- Extend the metal to 50–70% of its original deformation.
- Warm up the area construction hairdryer (up to 200–250°C) to relieve internal stress.
- Repeat the stretching until the geometry is completely corrected.
Stage 4. Straightening and grinding. After pulling, process the threshold straightening spoons from the inside, eliminating minor irregularities. Then sand the surface abrasive paper (granularity P120–P240) to prepare for painting.
What to do if the metal breaks while being pulled?
If cracks appear during the pulling process, stop immediately. Secure the threshold with clamps to prevent further metal creep. Then:
1. Drill the ends of the crack with a thin drill (∅2–3 mm) to stop the spread.
2. Clean the edges of the crack with a grinder at an angle of 45°.
3. Weld the defect semi-automatic (wire ∅0.8 mm) or glue epoxy resin with fiberglass (for temporary repairs).
4. After welding, tap off the seam round hammerto relieve tension.
5. Treatment after pulling: anti-corrosion and painting
The elongated threshold must be protected from repeated corrosion and restored to its aesthetic appearance. This step is often overlooked, but it is what determines the longevity of the repair.
Step 1. Degreasing. Wipe the threshold white spirit or antisiliconto remove traces of oil, wax and other contaminants. This will ensure good adhesion of anti-corrosion compounds.
Step 2. Applying primer. Apply to cleaned metal acid soil (for example, Reoflex Acid Primer) for protection against rust. Once dry (15–20 minutes), coat acrylic primer to level the surface.
Step 3. Anti-corrosion treatment. For the internal cavity of the threshold, use:
- 🛡️ Liquid anticorrosives (Dinitrol 409, Tectyl ML) - applied by spraying through technological holes.
- 🧲 Wax compounds (Waxoyl) - create an elastic film that prevents moisture from entering.
- 🔧 Movil with rust converter - if there are pockets of corrosion on the metal.
Step 4. Painting. If the threshold is not planned to be painted completely, it is enough local touch-up with the help aerosol can (choose color according to car code). For a complete repair:
- Apply 2-3 coats base enamel.
- After drying, cover varnish (for example, Mobihel HS).
- Polish the surface abrasive paste (for example, 3M 09374).
Anti-corrosion treatment of the internal cavity of the threshold must be repeated every 2-3 years, even if the external threshold looks intact. Humidity and salt from the roads gradually destroy the metal from the inside.
6. Common mistakes and how to avoid them
Even experienced craftsmen sometimes make mistakes when repairing thresholds. Here are the most common ones and how to prevent them:
| Error | Consequences | How to avoid |
|---|---|---|
| Pulling too hard | Metal rupture, formation of “humps” | Work smoothly, with breaks to cool the metal |
| Ignoring internal corrosion | Rust will continue to spread under the paint. | Treat the internal cavity with anti-corrosion agent before assembly |
| Wrong choice of grippers | Chips in paintwork, additional dents | Use soft attachments or pads |
| No geometry control | Curved threshold, problems closing doors | Check with a ruler after each step |
| Saving on primer | Paint peeling, bubbles after 1–2 years | Apply primer in 2-3 layers and let dry |
Another common problem is incorrect welding when repairing torn metal. If you are using semi-automatic, follow:
- 🔥 Current strength. For thresholds with a thickness of 0.8–1.2 mm, 60–90 A is sufficient.
- ⚡ Wire feed speed. Feeding too slowly will lead to burns.
- 🛡️ Shielding gas. Use argon or mixture argon/CO₂ (80/20).
If you doubt your welding skills, it is better to contact a professional or use cold welding (for example, Poxipol) for temporary repairs.
7. Features of working with aluminum thresholds
Aluminum thresholds (installed on Audi, BMW, Jaguar Land Rover etc.) require a different approach than steel ones. Main differences:
1. No heat treatment. Aluminum loses strength when heated above 150°C, therefore:
- 🔥 Do not use a torch or hair dryer to “release” the metal.
- 🛠️ Only work cold methods (reverse hammer, straightening spoons).
2. Special adhesives and sealants. The following is often used to repair aluminum thresholds:
- 🧪 Structural adhesives (3M 08115, SikaPower) - strength up to 30 MPa.
- 🛡️ Anti-corrosion sealants (Teroson EP 5055) - prevent galvanic corrosion.
3. Argon welding. If welding repair is required, use:
- 🔧 TIG machine (AC) with aluminum filler wire (ER 4043 or ER 5356).
- ⚡ Reverse polarity and high frequency ignition.
After repair, the aluminum threshold must be covered powder paint or liquid rubber for additional protection against oxidation.
⚠️ Attention: When working with aluminum, never use steel brushes or abrasives that have previously been used on steel. Iron particles remaining on aluminum will cause galvanic corrosion, which will destroy the metal in a few months.
8. When is it better to turn to professionals?
Despite the fact that many damage to thresholds can be repaired yourself, there are cases when repair at a service station is required:
1. Violation of body geometry. If after an accident the gaps between the door and the threshold have changed or the car is “driving” to the side, it is required bench check and professional straightening.
2. Through corrosion of more than 30% of the threshold area. In this case it is simpler and more reliable cut out the damaged area and weld a new one, rather than trying to “patch” the holes.
3. Thresholds with integrated security amplifiers. On many modern cars (for example, Volvo XC60, Mercedes E-Class) thresholds are part deformation zones and affect the operation of airbags. Their repair requires special equipment.
4. Aluminum or carbon fiber thresholds. If you do not have experience working with these materials, it is better to entrust the repair to specialists - mistakes will cost more.
Average cost of professional threshold repair at a car service:
| Type of work | Steel threshold | Aluminum threshold |
|---|---|---|
| Local dent pulling | 3 000–5 000 ₽ | 5 000–8 000 ₽ |
| Repair of through corrosion (patch) | 6 000–12 000 ₽ | 10 000–18 000 ₽ |
| Complete threshold replacement | 15 000–30 000 ₽ | 25 000–50 000 ₽ |
If you decide to repair the threshold yourself, but doubt your abilities, start with less noticeable area (for example, a rear sill) or practice on an unnecessary part.
Even if the threshold repair seems successful, check the geometry again after 1-2 weeks. The metal can “go back” due to internal stresses.
FAQ: Frequently asked questions about repairing thresholds
Is it possible to extend the threshold without welding?
Yes, if the deformation is minor (up to 3–4 cm) and the metal is not torn. To do this use reverse hammer with a vacuum suction cup or adhesive applicators (for example, PDR set). Also helps straightening from the inside using spoons. However, for deep dents or rusty sills, welding is often necessary to securely attach the grips.
Which reverse hammer is better to choose for DIY repairs?
Suitable for one-time repairs mechanical return hammer with a set of grips (price from 1,500 ₽). For regular use it is better to take hydraulic or pneumatic (from 5,000 ₽). Please note:
- 🔧 Cargo weight (optimally 1–2 kg for thresholds).
- 🔗 Type of grips (thresholds require narrow “hooks”).
- 🛡️ Handle material (rubber or plastic does not slip in your hands).
How to treat the threshold after pulling it out if it is not possible to paint it?
If painting is delayed, temporarily protect the metal:
- Apply acid soil (for example, Reoflex) to prevent rust.
- Cover anti-gravel (for example, Body 950) - it will create a protective film.
- Use vinyl film or liquid rubber (Plasti Dip) to mask damage.
These measures will extend the life of the threshold by 6–12 months, but full painting will still be required.
How to extend the threshold if there is no access from the inside (for example, on a monolithic body)?
In this case use "spot welding" method:
- Weld to the threshold repair washers (or self-tapping screws with caps) along the edges of the dent.
- Pin them down reverse hammer or slide hummer.
- Pull out the metal using smooth movements, controlling the geometry.
- After repair, cut off the washers and grind the welded areas.
For aluminum thresholds, instead of welding, use glue applicators (for example, 3M Pull Tab).
How long does it take to completely repair a threshold yourself?
The time depends on the complexity of the damage:
- 🕒 Local dent (without painting): 4–6 hours.
- 🕒 Perforation corrosion with patch: 8–12 hours (extended over 2–3 days, taking into account drying of the soil).
- 🕒 Complete threshold replacement: 14–20 hours (requires welding and painting).
Take your time - each stage (pulling, grinding, painting) must take place with technological pauses for the metal to cool and the materials to dry.