Bottom of car body Nissan Primera P12 is one of the most vulnerable areas, subject to constant exposure to moisture, reagents and mechanical shocks from sand and gravel. Over time, factory thresholds begin to rust, which not only spoils the appearance, but also reduces the overall rigidity of the structure, and also complicates the process of further welding or repair.
Owners Nissan Primera third generations are often faced with the need to replace rotten elements with new ones, since local repairs often turn out to be less effective and durable. Thresholds Nissan Primera P12 require special attention when choosing, since there are many options on the market made of different materials, and a mistake can lead to re-corrosion after just a couple of seasons.
In this article we will look in detail at how to choose suitable thresholds, what installation technologies exist and how to properly prepare the body for a long-lasting result. You will learn the difference between plastic linings and metal elements and why some owners prefer a complete replacement rather than just masking defects.
Why do the sills on the Nissan Primera P12 rot?
Body design features Nissan Primera P12 include the complex geometry of the lower parts of doors and arches, where water and dirt often accumulate. Factory anti-corrosion treatment is washed away over time, especially in regions with aggressive reagents, which starts the process of metal oxidation from the inside.
In addition, the standard thresholds are made of steel, which is susceptible to electrochemical corrosion when in contact with road salts. Mechanical damage to the paintwork when parking near curbs or during washing becomes entry points for moisture. If you notice blistering of the paint, this is a sure sign that the metal has already begun to deteriorate.
There are several key factors that accelerate destruction:
- ❄️ Using winter reagents that act as a rust catalyst.
- 🌧️ Lack of high-quality anticorrosive in hidden threshold cavities.
- 🛠️ Mechanical chips from stones, leaving bare metal vulnerable.
Ignoring these problems can lead to through corrosion, through which cold air and moisture begin to flow into the interior. Threshold repair on this model it is best to carry out this early to avoid costly replacement of the entire spar or floor.
⚠️ Attention: Do not try to simply paint over the rust on the thresholds Nissan Primera P12 without preliminary cleaning. This will only create the illusion of serviceability while the metal deterioration process continues under the paint layer, which will lead to bottom failure in the future.
Often, owners only notice corrosion when the sills begin to sag or peel off from the body. In that case replacement of thresholds becomes an inevitable procedure to restore the safety and aesthetics of the car.
Types of thresholds: plastic, metal or composite?
In the spare parts market for Nissan Primera P12 There are several types of underbody restoration solutions available. The choice depends on your goals: do you just want to protect the body from dirt or completely restore the geometry and rigidity of the car.
The simplest and cheapest option is plastic linings. They attach over existing thresholds and protect them from minor scratches and dirt. However, they do not solve the problem of internal corrosion and can create a “greenhouse” effect if moisture has accumulated underneath them.
Metal thresholds, on the contrary, require more complex installation, since they are welded to the body. They restore the rigidity of the structure and completely cover the old, rotten elements. Composite thresholds are a new trend, combining the lightness of plastic and the strength of metal, but they are still rare for P12.
Let's compare the main characteristics of different materials:
| Threshold type | Difficulty of installation | Corrosion protection | Effect on body rigidity |
|---|---|---|---|
| Plastic cover | Low (bolted/glued) | Medium (outside only) | Missing |
| Steel threshold (welded) | High (welding, straightening) | High (if properly processed) | Full recovery |
| Galvanized threshold | High (welding) | Very high | Full recovery |
| Composite (fiberglass) | Medium (bolts/glue) | High (does not rot) | Partial |
When choosing metal thresholds It is worth paying attention to the quality of the steel and the thickness of the metal. Cheap options made from thin sheet metal quickly deform and rust even faster than standard ones. Nissan Primera - a heavy car, and the thresholds must withstand serious loads when boarding and disembarking passengers.
- Price
- Durability
- Appearance
- Difficulty of installation
Body preparation and necessary tools
Before starting work on replacing the thresholds with Nissan Primera P12 It is necessary to carefully prepare the workplace and the car itself. 80% of the success of the entire operation depends on the quality of preparation. The body must be securely fixed, and all old coating must be removed to bare metal.
You will need a set of specialized equipment: a welding machine (preferably an inverter or semi-automatic), an angle grinder with cleaning and cutting discs, a drill with a set of metal drills, as well as a degreasing agent and an anti-corrosion primer. Don't forget about personal protective equipment: goggles, gloves and a respirator.
The process of removing old thresholds can be labor-intensive. They are often welded at several points or sealed with sealant. It is necessary to carefully cut off the old elements, being careful not to damage the body floor and side members. If the metal under the threshold has rotted, it will also have to be cut out and the inserts welded.
☑️ Preparation for replacing thresholds
Pay special attention to the internal cavity of the threshold. Even if everything seems fine on the outside, there may be a rust sponge inside. Use an endoscope or mirror to assess the extent of the disaster. Anti-corrosion treatment internal cavities is required before installing new parts.
If you plan to cook thresholds, make sure the room has good ventilation. Fumes from welding and old paints are toxic. Also check for flammable materials nearby. Nissan Primera P12 has complex wiring under the floor that can be easily damaged when cutting, so be extremely careful.
How to check the hidden cavity of the threshold?
Take a magnet on a wire and lower it inside. If the magnet does not stick or falls off, there is no metal inside. You can also use an endoscope connected to a smartphone for visual inspection.”
⚠️ Attention: Before starting welding work, be sure to disconnect the battery and remove the fuel pump. Sparks can ignite gasoline vapors if there is a leak in the system or fuel residues in the lines.
Step-by-step installation instructions
Installation of new thresholds on Nissan Primera P12 requires consistency and precision. First, try on the new parts and mark the cut and fit points. It is important that the gaps between the threshold and the door are uniform along the entire length.
Start by fixing the thresholds using clamps or temporary welding tacks. Do not try to weld all the seams at once. First, make sure that the body geometry is not compromised and that the doors close correctly. If the doors do not close, it means the threshold is not in place.
After precise adjustment, proceed to full welding. Use an interrupted weld to prevent the metal from overheating and warping. Heat the metal evenly, making small seams at intervals of 5-7 cm. This will prevent warping of the new part.
After welding, be sure to clean the seams with a grinder until smooth. Apply anti-corrosion primer to all welded areas. Then you can move on to puttying, if there are minor irregularities, and painting. The color must match the main body color.
Before painting, be sure to treat the welds with acid primer. A conventional primer will not be able to protect the metal from corrosion in places where the structure of the steel has been damaged when heated.”
If you are installing plastic trims, the process is simpler. Clean the surface, degrease and apply double-sided tape or special glue. Secure the linings with bolts, if provided by the design. Make sure all fasteners are tightened evenly.
Anti-corrosion treatment and painting
After installing new thresholds on Nissan Primera P12 A critical stage begins - protecting the metal. Without high-quality anti-corrosion treatment, even new thresholds will begin to rust in a couple of years. Use special compounds that penetrate the pores of the metal.
First, apply rust converter to all sanded areas. Then use 3 in 1 enamel primer, which creates a strong barrier. Pay special attention to the internal cavities - pour liquid wax or mastic there through the technological holes.
Painting should be done in several layers. The first layer is primer, the second is base, the third is varnish. Allow each coat to dry completely before applying the next. The quality of painting affects not only the appearance, but also the durability of the moisture protection.
Don't skimp on materials. Cheap paint can begin to peel off after just a season, allowing moisture to reach the metal. High quality painting - this is a guarantee that your investment in repairs will not be in vain.
Anti-corrosion treatment of the internal cavities of the threshold is as important as external painting. Moisture accumulates inside, causing hidden corrosion.”
Use primer-enamel for rust for primary processing and polyurethane varnish for finishing coat. This will ensure maximum resistance to mechanical damage and ultraviolet radiation.
Common mistakes and how to avoid them
Many owners Nissan Primera P12 make typical mistakes when replacing thresholds, which leads to rapid repeated destruction. One of the most common problems is insufficient metal cleaning before welding. The remaining rust will continue to eat away at the metal underneath the new layer.
Another mistake is improper welding. Excessive heating of the metal leads to its deformation and the appearance of cracks. If you do not know how to cook, it is better to entrust this work to professionals so as not to completely damage the body.
You should also avoid using cheap plastic covers on very rotten sills. This only masks the problem, creating conditions for even faster rotting due to the accumulation of moisture under the lining.
Don't forget about paint application technology. If you apply varnish to wet or insufficiently dry soil, the coating will quickly swell and fall off. Follow the material manufacturer's instructions and maintain temperature conditions.
⚠️ Attention: Never use regular bolts to fasten thresholds without rubber gaskets. The metal at the point of contact with the bolt will begin to rot due to an electrochemical reaction, especially in winter.
If you are not confident in your abilities, it is better to contact a specialized service. Professionals have experience working with Nissan Primera P12 and know all the nuances of its design, which will save you time and money.
FAQ: Frequently asked questions
Is it possible to replace thresholds without welding?
Yes, you can install plastic trims or bolted sills, but this will not restore the rigidity of the body and will not protect against internal corrosion. The welding method remains the most reliable.
How long does it take to replace thresholds?
If you have welding and body preparation skills, replacement takes from 1 to 3 days. If you order work from a service, the time frame may increase due to the queue and time for drying materials.
Do I need to remove the doors when replacing thresholds?
Doors are usually removed for ease of operation and to avoid accidental damage. This allows for better control of gaps and weld quality.
How often do you need to update the anticorrosive on thresholds?
It is recommended to check the condition of the anticorrosive agent once every 2-3 years and update it if necessary, especially after the winter season with abundant use of reagents.
Can I use regular bolts for fastening?
No, it is better to use galvanized bolts with rubber washers or special fasteners to avoid electrochemical corrosion at the contact points.
Replacing thresholds with Nissan Primera P12 is a serious job that requires attention to detail and adherence to technology. Correctly performed repairs will extend the life of your car for years, and high-quality painting will return it to its factory appearance. Do not delay solving the problem if you notice the first signs of corrosion.
Remember that high-quality anti-corrosion treatment of internal cavities is a key factor in the durability of thresholds. Even the most expensive metal will not save you if moisture accumulates inside. Regular inspection and care is the key to ensuring that your Nissan Primera will serve long and reliably.
Choose proven materials, do not skimp on surface preparation and entrust complex work to professionals. Then your car will look like new again and delight you with reliability in any road conditions.