EXPERT IN AUTO PARTS
25 November 2025 (updated) Table of Contents
The start-stop system of the BMW E91 shows frequent faults in the form of unreliable operation, whereby the system is either not activated or fails spontaneously. The weak points manifest themselves particularly in the 318i and 320d variants, where the system often shows its first faults after 60,000-80,000 kilometres. Typical symptoms are a permanent illumination of the start-stop warning light in the dashboard, the system does not switch off automatically when the vehicle is stationary or the engine does not restart automatically. The reliability of the system is affected by various factors, including battery sensor faults, software problems in the control unit or mechanical wear on the starter motor. The service life of the start-stop system depends heavily on driving conditions and maintenance.
A systematic check is essential for the Start-Stop system to function properly. The sensitive BMW E91 Start-Stop components require regular diagnosis with BMW-specific diagnostic equipment to read fault codes and check the battery capacity. To solve the problems, the battery sensor should first be checked and replaced if necessary, as this is often responsible for malfunctions. A software update of the engine control unit can also help, while mechanical defects in the starter motor may require replacement.
The air conditioning system in the BMW E91 typically develops problems in which it no longer cools properly or fails completely. These weak points occur particularly frequently after 80,000-120,000 kilometres and affect both the 318i and 325d models equally. Frequent faults are characterised by warm air despite the cooling being set, unusual noises when the air conditioning system is operating or complete failure of the system. The symptoms can occur gradually, with a gradual reduction in cooling performance, or suddenly due to complete system failure. Breakdowns are often caused by refrigerant loss due to leaking pipes, faulty compressors or worn condensers. The reliability of the air conditioning system is also affected by clogged cabin filters and a lack of maintenance.
Regular maintenance is crucial for the longevity of the air conditioning system. The complex BMW E91 air conditioning components require annual checks of the refrigerant level and system tightness to avoid costly repairs. Diagnosis is carried out by measuring the pressure in the refrigerant circuit and visually inspecting for leaks. To solve the problem, the refrigerant level should first be checked and topped up, while leaks must be localised and sealed. Regularly changing the cabin filter every 15,000-20,000 km prevents blockages and maintains optimum air circulation.
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-14%
Article number: 5011987001831
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£22.73
£19. 49
£19.49
for 1 litre
price incl. 20% VAT, excl. delivery costs
CASTROL Engine oil
5W-30, 5l
Article number: 15669E
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£57. 49
£11.50
for 1 litre
price incl. 20% VAT, excl. delivery costs
-53%
Article number: 1087.298.365
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compared to
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£520.93
£244. 50price incl. 20% VAT, excl. delivery costs
KOLBENSCHMIDT Crankshaft Bearing Set
Article number: 77953600
£66. 49price incl. 20% VAT, excl. delivery costs
LuK Clutch kit
with pilot bearing, with clutch release bearing, with release fork, with flywheel, with screw set, Requires special tools for mounting, with automatic adjustment
Article number: 600 0238 00
£470. 50price incl. 20% VAT, excl. delivery costs
The rear windscreen wiper of the BMW E91 exhibits characteristic failures, either not starting at all or only working intermittently. These problems typically manifest themselves after 70,000-100,000 kilometres of mileage and affect the reliability of the entire rear area. Common faults include a completely failed wiper motor, faulty relays or worn wiper rubbers that lead to streaking on the rear window. The symptoms range from the wiper stopping sporadically to coming to a complete standstill, with unusual noises often being heard from the rear area. Weak points lie particularly in the wiper motor itself, which is susceptible to the effects of weather and mechanical wear. Regular use and care of the wiper rubbers will significantly extend their service life.
A professional inspection is required to accurately diagnose the rear windscreen wiper problems. The BMW E91 rear wiper mechanisms require regular inspection of the electrical connections and motor housing for corrosion or water ingress. Troubleshooting begins with checking the fuses and relays, followed by measuring the voltage at the wiper motor. If the motor is faulty, a complete replacement is necessary, while relay problems often only require the relay to be replaced. Preventive measures include regular cleaning of the rear window and timely replacement of the wiper rubbers every 12-18 months.
The battery of the BMW E91 develops characteristic discharge problems, which manifest themselves in starting difficulties and remote control failures. These weak points occur particularly after 5-6 years of operation or in extreme temperatures, with the 320d models being affected more frequently due to their higher electrical load. Typical symptoms include weak engine starting, flickering dashboard lights or complete failure of the electrical systems. The remote control no longer functions reliably, resulting in poor signal range or complete inoperability. Frequent faults are caused by sulphation of the battery cells, defective battery sensors or parasitic power consumers in the vehicle. Reliability is further impaired by short journeys and long periods of inactivity, as the battery is not fully charged.
Professional maintenance is essential for the electrical systems to function optimally. The BMW E91 battery systems require regular capacity checks and voltage measurements in order to recognise deterioration at an early stage. Diagnosis is carried out by measuring the open-circuit voltage, load testing and checking the alternator charging system. If the battery is weak, a full charge with a suitable charger should be attempted first, while irreversible damage requires a battery change. The remote control can often be repaired by changing the battery in the remote control itself or reprogramming it on the vehicle.
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FEBI BILSTEIN Radiator hose
EPDM (ethylene propylene diene Monomer (M-class) rubber), Plastic, with quick couplers
Article number: 49252
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£24.99
£22. 99price incl. 20% VAT, excl. delivery costs
-61%
Article number: 37-161309
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£94.22
£35. 99
Price per item
£71.98 / Price per 2 items
price incl. 20% VAT, excl. delivery costs
SKF CV boot kit, drive shaft
146 mm, with clamps
Article number: VKJP 01001
£9. 99£19.98 / Price per 2 items
price incl. 20% VAT, excl. delivery costs
-8%
FEBI BILSTEIN Fuel cap
not lockable, Plastic, black, with support strap
Article number: 45550
compared to
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£17.99
£16. 49price incl. 20% VAT, excl. delivery costs
-35%
MAHLE EGR cooler
without gasket/seal, with EGR valve
Article number: CE 10 000P
compared to
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£730.62
£472. 50price incl. 20% VAT, excl. delivery costs
The bonnet of the BMW E91 has specific mechanical problems that manifest themselves in the form of sluggish opening or defective locking mechanisms. These breakdowns often occur after 100,000-150,000 kilometres and affect both the bonnet locking mechanism and the gas struts. Complaints include a bonnet that will not open, stiff operation of the opening lever or a bonnet that will not stay securely closed. The symptoms often develop gradually, starting with increased effort when opening and ending with complete failure of the mechanism. Weak points lie particularly in the gas struts, which lose their strength due to ageing and the effects of the weather, as well as in the locking mechanisms, which can become blocked due to corrosion or dirt. The reliability of the system depends heavily on regular care and lubrication of the moving parts.
Regular maintenance is crucial for the proper functioning of the bonnet mechanism. The BMW E91 bonnet components require semi-annual inspections of the gas struts and lubrication of all joints and locking points with suitable lubricants. Diagnosis begins with a visual inspection of all mechanical parts for wear, corrosion or damage. If the gas struts are weak, they must be replaced in pairs to ensure even lifting force. Blocked latches can often be restored to working order by thorough cleaning and lubrication, while irreparable damage will require replacement of the relevant components.
Based on the experience of BMW E91 owners, the following additional problems occur:
| Strengths | Weak points |
|---|---|
| Excellent driving dynamics | Start-stop system unreliable |
| High-quality workmanship | Air conditioning failures |
| Strong engine range | Rear windscreen wiper problems |
| Generous boot space | Battery discharge problems |
| Good road holding | Electronic faults |
| Comfortable equipment | High repair costs |
| Solid body quality | Bonnet mechanical defects |
The BMW E91 proves to be a fundamentally high-quality vehicle with convincing driving dynamics, but it has specific weak points in electronic and mechanical components. Most problems can be avoided or at least their effects limited by regular maintenance and early intervention. It is particularly important to observe the maintenance intervals and to use original parts or equivalent quality components for repairs.
MASTER-SPORT Link set, wheel suspension
Front Axle, Front Axle Right, Front Axle Left
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CASTROL Engine oil
5W-30, 4l
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EXIDE Battery
12V 72Ah 760A AGM Battery
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OPEL GM Engine oil
10W-40, 5l, Part Synthetic Oil
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FEBI BILSTEIN Rocker cover gasket
ACM (Polyacrylate)
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Valvoline Engine oil
5W-30, 4l
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WAHLER EGR valve
Electric, without fastening/mounting material
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MOBIL Engine oil
5W-30, 5l
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BERU Glow plug control module
Number of Cylinders: 6
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WAHLER EGR valve
Electric, without fastening/mounting material
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