Owners Nissan Almera G15 (also known as Nissan Almera K13 or Nissan Sunny N17 in some markets) often encounter problems with engine overheating or the interior taking a long time to warm up in winter. In 90% of cases, the **thermostat** is to blame - a small but critical element of the cooling system. Its malfunction leads to the fact that antifreeze circulates only in a small or large circle, disrupting the thermal balance of the motor.

Find the thermostat on Almera G15 with engines HR15DE (1.5 l) and HR16DE (1.6 l) is not difficult, but it requires removing several plastic elements from the engine compartment. This article contains a **exact location diagram** with a photo, signs of a malfunction, as well as step-by-step instructions for replacing it yourself. We will also look at why the thermostat may “stick” in the open or closed position and how to diagnose this without disassembling it.

Almera G15 cooling system design: where to look for a thermostat

B Nissan Almera G15 The thermostat is integrated into the **water pump housing** (pump), which is attached to the cylinder block on the timing belt side. This is a typical solution for modern engines Nissan-Renault, where the thermostat and pump form a single module. However, the thermostat itself is a removable part and can be replaced separately without touching the pump.

Key elements of the cooling system associated with the thermostat:

  • 🔹 Thermostat housing - a plastic or aluminum module into which the valve is built. On Almera G15 it is located to the right (in the direction of travel) of the engine, under the air duct.
  • 🔹 Pipes — 3-4 hoses fit to the body: from the radiator, heater, expansion tank and cylinder block.
  • 🔹 Temperature sensor - installed in or near the thermostat housing. Responsible for readings on the dashboard.
  • 🔹 Water pump — located under the thermostat, driven by the timing belt.

The photo below shows the exact location of the thermostat housing on Almera G15 with engine HR15DE (similar for HR16DE):

Photo of the location of the thermostat on Almera G15

The thermostat housing is circled in red. To get to it, you need to remove the air filter and disconnect the pipes. On the HR16DE engine, the appearance is identical, but the color of the plastic housing may differ.

Important: on some modifications Almera G15 (for example, for Southeast Asian markets) the thermostat housing may be metal. This does not affect the replacement process, but requires the use of sealant during reassembly.

Signs of a faulty thermostat: how to diagnose without disassembly

Thermostat on Nissan Almera G15 fails gradually, and its malfunction manifests itself through several symptoms. Main features:

  • ⚠️ The engine is overheating — the temperature arrow on the dashboard rises above normal (more than 90°C) even during short trips.
  • ⚠️ Long warm-up in winter — the stove blows cold air for more than 10 minutes after starting the engine.
  • ⚠️ Unstable temperature — the needle “jumps” from 70°C to 110°C for no apparent reason.
  • ⚠️ Cold lower radiator hose - when the engine is warm (if the thermostat is stuck in the closed position).

For an accurate diagnosis, perform a simple test:

  1. Start the cold engine and touch the upper radiator hose. It should remain cold until the engine warms up to 80–85°C.
  2. After reaching operating temperature (arrow in the middle of the scale), the pipe should become hot. If it stays cold - thermostat stuck in closed position.
  3. If the pipe heats up immediately after starting, the thermostat stuck open, and antifreeze circulates only in a large circle.
📊 What symptom of a faulty thermostat have you encountered?
  • The engine is overheating
  • The stove doesn't heat
  • Unstable temperature
  • Long warm-up
  • Other

⚠️ Attention: If the engine is overheating but the radiator hoses are hot, the problem may be faulty cooling fan or clogged radiator. In this case, the thermostat is most likely working.

Step-by-step instructions: how to get to the thermostat on Almera G15

To replace the thermostat, you will need to remove several components from the engine compartment. The work will take 1–1.5 hours if you have the tools. You will need:

  • 🔧 Set of sockets and keys (10 mm, 12 mm).
  • 🔧 Screwdriver with a Phillips bit.
  • 🔧 Pliers for clamps.
  • 🔧 New thermostat (original article number - 21200-4M50A for HR15DE/HR16DE).
  • 🔧 Antifreeze for topping up (1–1.5 l).
  • 🔧 Sealant (for example, Loctite 574 or Victor Reinz).

Sequence of actions:

  1. Drain the antifreeze:
    • Place a container under the radiator drain hole (bottom right).
    • Unscrew the cap on the radiator and let the fluid drain (about 3-4 liters).
    • Unscrew the expansion tank cap to speed up the process.
  2. Remove the air filter:
    • Disconnect the mass air flow sensor (MAF) connector.
    • Loosen the air duct clamp and remove the corrugation.
    • Unscrew the 3 bolts securing the filter housing (10 mm head).
  3. Disconnect the pipes:
    • Loosen the clamps on the pipes going to the thermostat housing (2-3 pieces).
    • Carefully pull off the hoses, placing a container for the remaining antifreeze.
  4. Remove the thermostat housing:
    • Unscrew the 3 housing mounting bolts (12 mm head).
    • Remove the housing and remove the old thermostat.

☑️ Preparing to replace the thermostat

Done: 0 / 5

⚠️ Attention: When removing pipes, avoid bending or twisting - on Almera G15 they often stick to the fittings. If the hose cannot be removed, carefully pry it off with a flat-head screwdriver after wetting the connection. WD-40.

Which thermostat to choose for replacement: original vs analogues

Original thermostat for Nissan Almera G15 has an article number 21200-4M50A (manufacturer - Nissan or Hitachi). Its average price is 1,800–2,500 rubles. However, there are high-quality analogues on the market that are cheaper:

Brand Article Opening temperature Price, rub. Notes
Nissan 21200-4M50A 82°C 1 800–2 500 Original, best quality
Gates TH22572 82°C 1 200–1 500 Reliable analogue, tested by owners
Mahle TH 30 82 82°C 1 400–1 700 High quality seals
Vernet TH6379.82 82°C 900–1 200 Budget option, possible fakes

When choosing a thermostat, pay attention to:

  • 🔹 Opening temperature - for Almera G15 she must be 82°C (indicated on the part body).
  • 🔹 Availability of O-ring — a rubber ring for sealing should be included with the thermostat.
  • 🔹 Manufacturer — avoid no-name brands (for example, Febi or Topran often counterfeited).
💡

Before purchasing, check that the thermostat is working: place it in a pan of water and heat it to 80°C. A working valve will begin to open at 82°C. If this does not happen, the part is defective.

Installation of a new thermostat and assembly: nuances for Almera G15

The process of installing a new thermostat is the reverse of removing it, but there are several critical points:

  1. Cleaning the seat:

    Remove any remaining old gasket from the housing and cylinder block. Use a plastic scraper to avoid damaging the aluminum. Treat surfaces with a degreaser (for example, Bravo).

  2. Installing the Thermostat:

    Place the thermostat in the housing with the spring facing towards the engine. Make sure that the O-ring lies flat and without distortion.

  3. Applying sealant:

    Apply a thin layer of sealant (eg Loctite 574) onto the adjacent surface of the housing. Do not use silicone sealants - they do not withstand high temperatures.

  4. Bolt tightening:

    Tighten the bolts crosswise firmly 10–12 Nm (do not overtighten so as not to strip the threads in the aluminum housing!).

  5. Connecting pipes:

    Make sure the clamps are tight but not pinched. On Almera G15 Spring clamps are often used - they can be tightened with pliers.

After assembly:

  • Add antifreeze (recommended Nissan Coolant L255N or analogues CoolStream A-110).
  • Start the engine and check for leaks.
  • Warm up the engine to operating temperature and make sure the heater is blowing hot air.
💡

After replacing the thermostat, be sure to remove any air pockets from the cooling system! To do this, squeeze the upper radiator hose several times with the engine running.

Common mistakes when replacing a thermostat and how to avoid them

Even experienced car owners make mistakes when replacing a thermostat with Almera G15. Here are the most common of them:

  • 🚫 Using the wrong sealant - silicone compounds (for example, ABRO) eventually dry out and leak. Use only specialized sealants for cooling systems.
  • 🚫 Re-tightening of body bolts - The aluminum thermostat housing is easy to crack. Maximum force - 12 Nm.
  • 🚫 Incorrect O-ring installation - if the ring is skewed, antifreeze will leak. Before installation, lubricate it with a thin layer of sealant.
  • 🚫 They forget to bleed air - air pockets lead to overheating. After replacing the thermostat, compress the radiator hoses several times.
  • 🚫 Buy a thermostat with the wrong opening temperature - for Almera G15 need part for 82°C, not 88°C or 92°C.

⚠️ Attention: If the engine continues to overheat after replacing the thermostat, check:

  • Performance cooling fan (it should turn on at 95–100°C).
  • Condition radiator — clogged honeycombs or damaged pipes reduce cooling efficiency.
  • Level antifreeze - If the liquid level is low, the thermostat will not be able to regulate the temperature correctly.

FAQ: Frequently asked questions about the Nissan Almera G15 thermostat

Is it possible to drive with a faulty thermostat?

Short term - yes, but with caution. If the thermostat is stuck in open position, the engine will take longer to warm up, but there will be no overheating. If stuck in closed position — the risk of overheating and damage to the cylinder head is very high. In this case, you cannot drive.

How often do you need to change the thermostat on Almera G15?

The thermostat is not a consumable, and its replacement is not regulated. However, in practice it fails every 80–120 thousand km or 5–7 years of operation. Signs of malfunction (overheating, long warm-up) are a reason to check.

Is it possible to clean the thermostat instead of replacing it?

No. A thermostat is a valve with a heat-sensitive element (wax) that degrades over time. Cleaning will not restore its functionality. The only option is replacement.

What antifreeze should I fill in after replacing the thermostat?

For Nissan Almera G15 antifreeze recommended Nissan Coolant L255N (green) or its analogues: CoolStream A-110, Sintec Unlimited G12+. The volume of the system is 6.5 l, but when replacing the thermostat, it is enough to add 1–1.5 l.

How much does it cost to replace a thermostat at a service center?

The cost of work in the service is from 1,500 to 2,500 rubles (depending on the region). Taking into account the price of the thermostat (21200-4M50A — ~2,000 rub.) the total amount will be 3,500–4,500 rubles. Replacing it yourself will save you money on work.