1. Introduction
This manual provides essential information for the installation, operation, and maintenance of your new BMW Coolant Expansion Tank with an integrated Coolant Level Sensor. The expansion tank is a critical component of your vehicle's cooling system, designed to manage coolant volume changes due to temperature fluctuations and to provide a reservoir for coolant. The integrated level sensor alerts you to low coolant conditions, helping to prevent engine overheating and potential damage.
1.1. Compatibilité
This coolant expansion tank with level sensor is compatible with the following BMW models:
- BMW E46
- BMW E53
- BMW E83
- 320i, 323Ci, 323i
- 325Ci, 325i, 325xi
- 328Ci, 328i
- 330Ci, 330i, 330xi
- X3, X5
2. Produit terminéview
The coolant expansion tank is constructed from durable plastic, designed to withstand the high temperatures and pressures of the engine cooling system. It features an integrated coolant level sensor, which is typically made with robust materials like stainless steel for longevity and accurate readings. The tank includes connections for coolant hoses and a cap for filling and pressure regulation.

Image 1 : Gros plan view of the integrated coolant level sensor.

Image 2: The coolant expansion tank, showing its main body, cap, and level sensor.
3. Guide d'installation
Proper installation is crucial for the safe and effective operation of the cooling system. If you are not experienced with automotive repairs, it is highly recommended to seek professional assistance.
3.1. Précautions de sécurité
- Ensure the engine is completely cool before beginning any work on the cooling system. Hot coolant can cause severe burns.
- Portez un équipement de protection individuelle approprié, notamment des gants et des lunettes de protection.
- Débranchez la batterie du véhicule pour éviter tout court-circuit accidentel.
- Éliminez le liquide de refroidissement usagé de manière responsable, conformément à la réglementation locale.
3.2. Étapes d'installation (Généralités)
- Vidangez le liquide de refroidissement : Place a drain pan under the radiator and open the drain plug to drain the coolant.
- Retirer l'ancien réservoir : Disconnect all hoses connected to the old expansion tank. Unclip or unbolt the old tank from its mounting bracket.
- Installer le nouveau réservoir : Position the new expansion tank in the mounting bracket and secure it. Connect all hoses to their respective ports on the new tank, ensuring clamps sont serrés.
- Installer le capteur : If the sensor is not pre-installed, insert the coolant level sensor into its designated port on the tank and secure it. Connect the electrical connector to the sensor.
- Remplissage du liquide de refroidissement : Close the radiator drain plug. Slowly fill the expansion tank with the correct type and mixture of BMW-approved coolant.
- Purge d'air : Follow your vehicle's specific procedure for bleeding air from the cooling system. This often involves running the engine with the heater on high and the expansion tank cap off until no more bubbles appear.
- Vérifiez les fuites : After bleeding, inspect all connections for leaks.
- Essai routier : Take a short test drive, monitoring the temperature gauge. Recheck coolant level and for leaks after the engine cools.
Vidéo 1 : Terminéview of the Coolant Expansion Tank and its components, useful for understanding installation points.
4. Fonctionnement
The coolant expansion tank maintains the correct pressure within the cooling system and provides a space for coolant to expand and contract with temperature changes. The integrated coolant level sensor continuously monitors the coolant volume. If the coolant level drops below a safe threshold, the sensor triggers a warning light on your vehicle's dashboard, indicating that coolant needs to be added.
4.1. Monitoring Coolant Level
Regularly check the coolant level in the expansion tank when the engine is cold. The tank typically has 'MIN' and 'MAX' markings. The coolant level should be between these two marks. If the level is consistently low, investigate for leaks or consult a professional.
Vidéo 2 : Détails view of the coolant level sensor, demonstrating its design and function.
5. Entretien
To ensure the longevity and optimal performance of your cooling system, regular maintenance is essential.
5.1. Contrôles réguliers
- Inspection visuelle : Periodically inspect the expansion tank for cracks, discoloration, or signs of leaks. Check hoses for cracks or swelling.
- Niveau de liquide de refroidissement : Check the coolant level weekly or bi-weekly, especially before long trips.
- Inspection du bouchon : Ensure the expansion tank cap is securely tightened and that its rubber seal is in good condition. A faulty cap can lead to pressure loss and overheating.
5.2. Coolant Type
Always use BMW-approved coolant (typically a blue or green ethylene glycol-based coolant) mixed with distilled water according to the manufacturer's specifications. Using incorrect coolant can damage the cooling system components.
6. Dépannage
Below are common issues and potential solutions related to the coolant expansion tank and level sensor.
| Problème | Cause possible | Solution |
|---|---|---|
| Low Coolant Warning Light On | Low coolant level, faulty sensor, electrical connection issue. | Check coolant level and add if necessary. Inspect sensor wiring. If level is correct, sensor may need replacement. |
| Coolant Leak from Tank | Cracked tank, loose hose connections, faulty cap. | Inspect tank for cracks; replace if found. Tighten hose clamps. Replace expansion tank cap. |
| Surchauffe du moteur | Low coolant, air in system, other cooling system issues. | Check coolant level. Bleed air from the system. Consult a mechanic for further diagnosis. |
7. Spécifications
Key technical specifications for the BMW Coolant Expansion Tank with Level Sensor.
| Fonctionnalité | Détail |
|---|---|
| Marque | BMW |
| Matériel | Plastic (Tank), Stainless Steel (Sensor components) |
| Type de montage | Montage à bride |
| Output Type (Sensor) | Pousser tirer |
| Sensing Distance (Sensor) | 12 pouces |
| Indice de température supérieur | 125 degrés Celsius |
| Numéro de pièce du fabricant | 17117573781 |
| Numéro de pièce OEM | 17 11 7 573 781 |
8. Garantie et assistance
Pour toute information relative à la garantie et pour obtenir une assistance technique, veuillez consulter la documentation fournie avec votre achat ou contacter directement le vendeur. Conservez votre preuve d'achat pour toute réclamation au titre de la garantie.