Water in the trunk of a <em>Nissan Sunny</em>: how to find and fix the leak

Nissan Sunny — a reliable and unpretentious car, but even it has weaknesses. One of the most common is water accumulation in the trunk. Owners often discover puddles under a rug or rust on metal without understanding where the moisture comes from. In this article, we will analyze all the possible causes of leaks, learn how to diagnose the problem and fix it without extra costs.

Water in the trunk is not just a discomfort, but a real threat: body corrosion, short circuit in electrical wiring, unpleasant odor and mold. If you ignore the problem, repairs will cost many times more than timely prevention. We've collected proven methods for finding the source of a leak, instructions for sealing, and tips for caring for seals.

Why in the trunk? Nissan Sunny water appears: main reasons

The accumulation of moisture in the luggage compartment is rarely an accident. This is usually the result of design issues or worn seals. Here are the most common reasons:

• 🚗 Clogged drain holes in the rear arches or under the spare wheel. They are designed to drain water, but over time they become clogged with dirt and leaves.
• 🔧 Worn rear door or fuel filler flap seals. Rubber loses its elasticity, microcracks appear through which water leaks.
• 💧 Leaks through taillights. The sealant dries out over time, and condensation accumulates inside the headlight housing, flowing into the trunk.
• 🛠️ Body damage after an accident or corrosion. Even a small dent can break the seal.
• 🌧️ Incorrect installation of additional equipment, for example, a towbar or an alarm system, in which the integrity of the seals is compromised.

On Nissan Sunny (especially models B13, B14 And B15) water most often enters through the drainage holes under the spare tire. The design of the trunk is such that moisture does not evaporate quickly, but accumulates under the mat. If you don't clean the drainage every six months, the problem is guaranteed.

Another “weak” unit is the rear door seal. On cars older than 10 years, the rubber becomes dull, and when the door is closed, gaps remain. This is easy to check: in rainy weather, inspect the joints of the door and the body for smudges.

How to detect the source of a leak: step-by-step diagnostics

Before you can fix the problem, you need to determine exactly where the water is coming from. Here is the algorithm of actions:

1. Remove everything from the trunkincluding carpet and spare tire. Dry the surface thoroughly.
2. Inspect the trunk for rust. Foci of corrosion often indicate areas of constant moisture accumulation.
3. Check the drainage holes. They are located under the spare wheel (on some models - in the rear arches). Clean them with wire or compressed air.
4. Use the smoke test: Close the trunk and blow smoke from inside (for example, from a smoke bomb). Places where smoke escapes are potential sources of leakage.
5. Water the trunk with a hose, simulating rain. An assistant inside the machine must monitor where the water comes from.

Pay special attention to:

• 🔦 Rear door seal - run your finger over it, checking its elasticity. If the rubber is hard or cracked, it needs to be replaced.
• 🔦 Rear light mounts. Remove the headlights and check the condition of the sealant. Often water seeps through microcracks in the plastic.
• 🔦 Gas tank flap. The seal here is small, but if it is worn out, water will flow directly into the trunk.

On Nissan Sunny B14 often leaks through the technological holes for the wiring of the rear lights. They can be found by removing the trunk trim. If there is no factory sealing, you will have to apply it yourself.

Remove the carpet and spare wheel|Dry the trunk with a hairdryer|Inspect the drainage holes|Check the door and light seals|Simulate rain with a hose-->

What to do if water is already in the trunk: emergency measures

If you find a puddle in the trunk, you need to act quickly to prevent corrosion and damage to the electrical wiring. Here's what to do immediately:

1. Remove all water sponge or vacuum cleaner. Do not leave even small puddles - they will lead to rust.
2. Dry the trunk with a hair dryer or leaving the car in the sun with the trunk open for 2–3 hours.
3. Treat the metal with an anti-corrosion compound, for example, WD-40 or Movilem. Be especially careful with welds and fastening points.
4. Check the wiring. If water gets on the fuse boxes or wires, they need to be dried and checked with a multimeter for a short circuit.

On Nissan Sunny models with rear independent suspension, water often accumulates in the niches under the shock absorbers. These areas are difficult to dry, so after removing moisture they need to be treated with a cavity preservative (for example, Dinitrol ML).

If there is already a moldy smell in the trunk, use special cleaners (for example, OdorGone) or folk remedies - vinegar solution or soda powder. Apply the product to the surface, then rinse and dry.

⚠️ Attention! If water gets on the rear light control unit (located under the trunk trim), do not turn on the ignition until it is completely dry. A short circuit can damage the entire unit.

How to fix a leak: repair and sealing

Once the source of the leak has been found, begin repairs. Remedies depend on the cause:

Cause of leakage	Required materials	Repair instructions
Clogged drain holes	Wire, compressed air, silicone grease	Clean the holes, rinse with water, treat with silicone to protect against icing.
Worn door seal	New seal (part number for Sunny B14: 80410-4M000), glue 3M 08008	Remove the old seal, clean the surface, glue a new one, heating it with a hairdryer for better adhesion.
Leaking through tail light	Sealant ABRO WS-904, degreaser, spatula	Remove the canopy, remove the old sealant, apply a new layer, and install the canopy back.
Corrosion of drainage channels	Rust converter Tsinkar, anticorrosive Dinitrol 490	Remove rust, treat with converter, apply anti-corrosion coating.

To replace the rear door seal with Nissan Sunny it will take about 2 hours. The main thing is to choose the right part number. For models B13 And B14 suitable seal from Nissan Primera P11 (article 80410-4M100), since they are unified.

If leakage occurs through welded seams, they can be additionally coated silicone sealant or liquid rubber. But this is a temporary solution - it is better to weld the seams as soon as possible.

Leak prevention: how to protect the trunk from water

It is better to prevent a problem than to deal with its consequences. Here's what will help you avoid water accumulation in the trunk Nissan Sunny:

• 🔄 Clean drain holes every 6 months (spring and autumn). Use compressed air or thin wire.
• 🧴 Treat seals silicone grease (Liqui Moly Silicon-Spray) once a season. This will prevent the rubber from cracking.
• 🚿 Wash your car correctly: Do not direct high-pressure water jets at the joints of doors and skylights.
• 🔧 Check for leaks after any body repair or installation of additional equipment.
• 🌡️ Use desiccant (For example, Silica Gel) in the trunk if the car is often parked in a humid climate.

It is recommended to treat the drainage holes for the winter deicer (For example, Hi-Gear HG5501) so that they do not freeze and become clogged with ice. It is also a good idea to remove the trunk trim once a year and check the condition of the metal underneath.

If you frequently transport items that could scratch the seal (such as bicycles or construction materials), place them in the trunk PVC protective mat. It will prevent mechanical damage and additional moisture accumulation.

⚠️ Attention! Do not use petroleum products (for example, diesel fuel or gasoline) to treat seals. They destroy rubber and accelerate its wear.

What happens if you ignore water in the trunk?

Many owners Nissan Sunny They drive for years with a “wet” trunk, unaware of the consequences. Meanwhile, even a small amount of water can lead to serious problems:

• 🔥 Body corrosion. Rust eats away at metal from the inside, especially around welds. After 2-3 years, this can lead to through holes.
• ⚡ Short circuit. Water gets on the wiring, the contacts oxidize, which leads to malfunctions of the lights, alarms, or even the on-board computer.
• 🤢 Mold and mildew. A humid environment is ideal for bacteria to grow. A persistent smell of dampness will appear in the cabin, which is difficult to remove.
• 💰 Reducing the cost of a car. When selling, a rusty trunk will become a serious bargaining point.

On Nissan Sunny B15 The rear arch on the gas tank side often suffers. Water accumulates in the niche where corrosion begins and then spreads to the side members. Repairs will cost 15–20 thousand rubles, while prevention (cleaning drainage and anticorrosive treatment) costs 10 times less.

Another danger - water freezing in winter. Ice in the drainage holes blocks the outflow of moisture, and the next time it warms up, water will flood the trunk even more. In addition, as ice expands, it can damage plastic trim elements.

What to do if rust has already appeared?

If the corrosion is superficial (only on the top layer of metal), it can be removed rust converter (For example, Tsinkar) and cover primer with zinc. If the rust is deep (through holes), welding and patching will be required. On Nissan Sunny most often rot:

- sills under the rear arches,

- mounting locations for rear shock absorbers,

- niche under the spare wheel.

For precise repairs, it is better to contact a body shop with equipment for spot welding.

FAQ: Frequently asked questions about water in the trunk Nissan Sunny

Is it possible to drive if there is some water in the trunk?

In the short term, yes, but it is fraught with consequences. Even a small puddle will lead to corrosion if not eliminated. In addition, water may get into the electrical wiring, causing the lights or alarm to malfunction. We recommend drying the trunk and finding the source of the leak within a week.

How much does it cost to replace a rear door seal? Nissan Sunny?

The cost depends on the model:

• Sunny B13/B14: the seal will cost 1,500–2,500 rubles, the work will cost 1,000–1,500 rubles.
• Sunny B15: the part is more expensive - 2,500–3,500 rubles, work - up to 2,000 rubles.

You can save money by purchasing a seal from Nissan Primera (article 80410-4M100) - it fits in size and costs less.

What sealant is best to use for taillights?

Optimal options:

• ABRO WS-904 - inexpensive, but reliable, withstands temperature changes.
• Dow Corning 7091 — professional sealant, used at service stations.
• Permatex 81160 — dries quickly, suitable for emergency repairs.

Before applying sealant, be sure to remove the old layer and degrease the surface. White spirit.

What should I do if water gets into the fuse box?

Disconnect the battery immediately! Then:

1. Remove the fuse box and dry it with a hairdryer (temperature no higher than 60°C).
2. Check fuses and relays for oxidation. Replace if necessary.
3. Process contacts contact lubricant (For example, Liqui Moly Kontaktreiniger).
4. Reinstall the unit only after complete drying (at least 12 hours).

If after these manipulations you still have electrical problems, contact an auto electrician.

Is it possible to weld rusty seams in the trunk yourself?

Theoretically, yes, but only if you have welding experience. For Nissan Sunny important:

• Use spot welding or semi-automatic in carbon dioxide environmentso as not to burn the metal.
• Before welding, completely remove rust and treat the metal zinc primer.
• After welding apply epoxy primer And anti-gravel coating.

If you have no experience, it is better to entrust the work to a professional - mistakes during welding will lead to even greater corrosion.