Heater radiator <em>Nissan Sunny FB15</em>: how to diagnose and fix problems

Nissan Sunny FB15 is a legendary Japanese sedan that has gained popularity due to its reliability and unpretentiousness. However, even such machines have weak points, and one of them is heater radiator. Over time, it becomes clogged, leaks, or corrodes, leaving the driver without interior heating during the cold season. In this article, we will look at how to independently diagnose faults, select spare parts and replace the heater radiator without contacting service.

Feature FB15 — compact design of the heater, which complicates access to the radiator. But with the right approach, the work can be completed in a garage in 3–5 hours. We have collected all the relevant information: from signs of breakdown to step-by-step instructions with nuances, which you will not find in standard manuals. We will also consider what analogues of the original radiator fit best and how to avoid mistakes when replacing.

Signs of a malfunctioning heater radiator Nissan Sunny FB15

The first symptoms of heater core problems are often attributed to the thermostat or pump, but there are key differences. If the heater blows cold air and the engine is warmed up to operating temperature, the radiator is to blame. Here are the main signs:

• 🔥 Cold air from deflectors with the heater on and the engine warm (even at maximum temperature).
• 💧 Antifreeze puddles under the feet of the driver or passenger - a sign of a radiator leak.
• 🌫️ Fogging of glass from the inside for no apparent reason (evaporating antifreeze settles on the glass).
• 🚗 Sweetish smell in the cabin - antifreeze or antifreeze seeps through microcracks.
• 🔧 Frequent drop in coolant level no external leaks under the hood.

On Sunny FB15 The heater radiator is especially vulnerable due to its design features: it is located low, and when driving off-road, dirt gets on it, accelerating corrosion. In addition, over time, the radiator cells become clogged with antifreeze deposits, which reduces heat transfer. If you ignore these symptoms, you may experience engine overheating — the coolant will go into the cabin and not circulate through the system.

⚠️ Attention! If antifreeze gets on the interior carpet, remove it immediately with a damp cloth. Antifreeze is toxic and can cause skin irritation and damage plastic interior elements.

Diagnostics: how to pinpoint the problem

Before buying a new radiator, make sure that this is the problem. On FB15 A cold stove may be due to:

• 🔄 Air in the cooling system (after antifreeze replacement or repair).
• 🚪 Faulty stove tap (on Sunny it often jams or leaks).
• 🔥 Clogged cabin filter (restricts air flow).
• 🔧 Damage to the damper or heater control drive.

To rule out these options, check:

1. Check the antifreeze level in the expansion tank. If it falls, but there are no leaks under the hood, look for a leak in the cabin.
2. Start the engine, warm up to operating temperature and turn on the stove to maximum. If the air is cold and the heater radiator pipes (under the panel) are hot, the radiator is clogged.
3. Look around the interior under the feet of the driver and passenger. Wet spots or white deposits (from evaporated antifreeze) are a sure sign of a leak.
4. Check the heater faucet. On FB15 it is located under the hood, on the pipe leading into the cabin. If the faucet does not open or leaks, the problem is in it, not in the radiator.

If all signs point to the radiator, proceed to replace it. But first you need choose the right spare part - more on this in the next section.

Choosing a stove radiator: original vs analogues

Original heater radiator for Nissan Sunny FB15 has an article number 27200-4M000 (for models with air conditioning) and 27200-4M001 (no air conditioning). The cost of the original is from 8,000 to 12,000 rubles, which seems overpriced to many. Fortunately, there are proven analogues:

Brand	Article	Price, rub.	Features
Denso	DRH0144	5 500–7 000	High quality, full analogue of the original, copper tubes
Nissens	941013	4 800–6 200	Good heat dissipation, but thin walls (smaller resource)
Mahle	OH 373 002	6 000–7 500	Reinforced design, suitable for harsh winters
NRF	52104	3 500–4 500	Budget option, but there are frequent cases of leaks after 1–2 years
Tama	TRH-0144	4 200–5 500	Good price/quality ratio, popular in Russia

When choosing an aluminum radiator (for example, Nissens or NRF) keep in mind that it is lighter and cheaper than copper, but less durable. Copper radiators (Denso, Mahle) last longer, transfer heat better and are easier to repair (soldering). If you plan to use Sunny FB15 for a long time, it’s better to overpay for copper.

⚠️ Attention! When purchasing a radiator, check whether it is suitable for your modification: with or without air conditioning. Models with climate control may have different mounts and pipes.

On Nissan Sunny FB15 Two types of heater radiators were installed from the factory: with plastic tanks (early releases) and with aluminum (late ones). When replacing, you can install any type, but aluminum ones are less susceptible to cracking from vibrations.

Preparing for replacement: tools and consumables

Replacing the heater radiator with FB15 requires partial disassembly of the panel, so prepare in advance:

• 🔧 Tools:
  • Set of sockets and keys (10, 12, 14 mm).
  • Screwdrivers (phillips, flat, short for hard-to-reach places).
  • Pliers and wire cutters.
  • A hacksaw or grinder (for cutting pipes if they are stuck).
  • Flashlight with magnet (lighting in panel niches).
• 🛠️ Consumables:
  • New heater radiator (with a suitable part number).
  • Antifreeze (2-3 liters for topping up, preferably the same one that is poured into the system).
  • Stove pipes (2 pcs., article number 27253-4M000 And 27254-4M000).
  • Clamps (4–6 pcs., preferably screw ones).
  • Cooling system sealant (eg ABRO or Loctite 577).
  • Rags and container for draining antifreeze.

You will also need remove the front panel, so clear the salon of unnecessary things in advance. If you have service manual for Sunny FB15, keep it handy - there are panel mounting diagrams there. If there is no manual, take photographs of each stage of disassembly so as not to confuse the wires and fasteners during reassembly.

Drain the antifreeze from the system|Disconnect the battery terminal|Remove the glove compartment and the lower part of the panel|Disconnect the pipes from the radiator|Prepare a container for old antifreeze-->

Step-by-step instructions for replacing the heater radiator

The process of replacing the radiator with Nissan Sunny FB15 can be divided into 3 stages: interior disassembly, dismantling the old radiator And installation of new. Let's look at each in detail.

Stage 1: Panel Disassembly

This is the most time-consuming stage. On FB15 The panel is not completely removed, but only its lower part. Proceed like this:

1. Drain the antifreeze from the system through the tap on the cooling radiator or the lower pipe.
2. Disconnect the battery (remove the negative terminal).
3. Remove the glove compartment:
   • Unscrew the 3 screws from the bottom (under the plastic plug).
   • Pull the glove compartment towards you and disconnect the backlight bulb.
4. Remove the bottom of the panel:
   • Unscrew the 2 bolts under the glove compartment and the 2 self-tapping screws under the steering wheel (the plugs can be pryed off with a screwdriver).
   • Remove the plastic trim under the instrument panel (held on by latches).
   • Disconnect the connectors from the buttons and sensors (memorize or photograph the location).

Unscrew the metal radiator protection (4 10mm socket head bolts).

You should now have free access to the stove radiator. It is located behind a metal protection; two pipes approach it (antifreeze inlet and outlet).

Stage 2: Removing the old radiator

Carefully disconnect the hoses from the radiator. They may stick, so:

• If the pipes cannot be removed, cut them with a hacksaw closer to the radiator, and put on new ones later.
• Place the container - the remaining antifreeze will flow out of the pipes.
• Unscrew the 3 radiator mounting bolts (two on top, one on bottom).
• Pull the radiator towards you, tilting it down (so as not to damage the air conditioning pipes, if any).

Inspect the old radiator: if it is clogged with dirt, you can try to flush it special liquid (For example, LIQUI MOLY Kuhler-Reiniger). However, if there are cracks or severe corrosion, washing will not help - only replacement.

Stage 3: Installing a new radiator

Before installing a new radiator:

1. Clean the seat from dirt and old sealant.
2. Apply a thin layer of sealant on the rubber seals of the new radiator.
3. Install the radiator into place, secure with bolts (do not overtighten!).
4. Connect new pipes, tighten the clamps.
5. Fill with antifreeze (through the expansion tank) and remove any air pockets by opening the heater tap.

After assembling the panel check the operation of the stove:

• Start the engine, warm up to operating temperature.
• Turn on the stove to maximum - the air should be hot.
• Check for antifreeze leaks in the cabin.

Typical replacement mistakes and how to avoid them

Even experienced car owners make mistakes that lead to repeated disassembly or breakdowns. Here are the most common:

• 🔧 Incorrect panel assembly — forgotten bolts or unconnected connectors lead to squeaks or non-functioning buttons.
• 💧 Incomplete drainage of antifreeze — when the pipes are disconnected, liquid flows into the cabin, damaging the electronics.
• 🔥 Re-stretching clamps — pipes can burst, especially if they are old.
• 🌡️ Airing the system — the stove doesn’t heat up until you expel the air through the faucet.
• 🔄 Using low-quality sealant - it can clog the cooling system.

To avoid problems:

• Take pictures of every step of disassembly - this will help to assemble the panel correctly.
• Use only screw clamps - they are more reliable than spring ones.
• Flush the cooling system before adding new antifreeze (especially if the old one was dirty).
• Check the operation of the stove immediately - if the air is cold, it means there is air left in the system.

If after replacing the radiator the stove heats poorly, check:

• Antifreeze level (must be between MIN and MAX).
• The functionality of the stove tap (the cable should move freely).
• Lack of air in the system (when the engine warms up, the pipes should be hot).

What should I do if the heater blows cold after replacing the radiator?

If the radiator pipes are hot and the air is cold, the problem is in the damper or heater control actuator. If the pipes are cold, there is air left in the system. To remove it:

1. Start the engine, warm up to operating temperature.
2. Open the stove faucet (if equipped).
3. Remove the hose from the throttle body and wait until antifreeze comes out of it.
4. Close the hose and add antifreeze to the level.

Prevention: how to extend the life of a stove radiator

To keep the heater radiator on Nissan Sunny FB15 lasted longer, follow simple recommendations:

• 🔄 Change antifreeze every 2 years or 40,000 km. Over time, it loses its properties and causes corrosion.
• 🚗 Avoid driving through deep puddles — water and dirt get on the radiator, accelerating its wear.
• 🌡️ Check the antifreeze level once a month. A drop in level is the first sign of a leak.
• 🔧 Flush the cooling system when replacing antifreeze (with special means, not water!).
• 🛠️ Lubricate the heater tap cable once a year (for example, WD-40) so that it doesn't get stuck.

If you often drive off-road, install engine protection with an additional partition for the stove radiator. This will protect it from impacts and dirt. It is also useful to check once a season condition of the pipes - they should be soft, without cracks.

If the antifreeze in the system has not been changed for a long time, it can turn into a thick slurry that will clog the radiator. In this case it will help complete flushing of the system:

1. Drain the old antifreeze.
2. Fill in flushing fluid (for example, LAVR Radiator Flush Classic).
3. Start the engine and let it run for 10–15 minutes.
4. Drain the rinse and repeat the procedure with clean water.
5. Refill with new antifreeze.

Frequently asked questions (FAQ)

Is it possible to repair a stove radiator? Nissan Sunny FB15, if it flows?

Theoretically, you can solder a copper radiator, but in practice this is a temporary solution. Aluminum radiators are more difficult to solder, and repairs are often more expensive than new ones. If the leak is severe or the radiator is clogged, it is better to replace it.

How much antifreeze is needed to replace a heater radiator?

For Sunny FB15 The total volume of the cooling system is about 6 liters. When replacing the heater radiator, 1.5–2 liters are consumed (this is how much is drained when the pipes are disconnected). You need to add the same antifreeze that is poured into the system (you cannot mix different types!).

How to check if the stove tap is working?

On FB15 The stove valve is controlled by a cable from a lever on the panel. To check its functionality:

1. Remove the bottom of the panel (as when replacing a radiator).
2. Pull the cable by hand - it should move freely.
3. If the tap does not open or is leaking, it needs to be replaced (part number 27260-4M000).

Is it possible to drive with a faulty heater radiator?

Technically it is possible, but it is fraught with consequences:

• Antifreeze will leak into the cabin, damaging the carpeting and electronics.
• In case of severe leakage it is possible engine overheating due to lack of coolant.
• There will be a constant smell of antifreeze in the cabin, which is harmful to health.

We recommend replacing the radiator at the first sign of trouble.

What kind of antifreeze to pour into Nissan Sunny FB15?

Filled from the factory green antifreeze based on ethylene glycol (specification Nissan Long Life Coolant or analogues: CoolStream A-110, Sintec Unlimited G11). Do not mix with red (G12) or yellow (G13) antifreeze!