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Common BMW Problems
Check engine light on? Engine running rough? Here you will find some answers to the most frequently diagnosed BMW problems brought into our BMW repair shops. We do not recommend you assume that the answer here directly relates to your car. Accurate diagnosis of a problem typically saves you money. And, you should know that often third parties will misdiagnose a car for what appears to be similar problems or related diagnostic codes.
Coolant Leak From Around The Water Pump – 7 Series
If you start to experience a coolant leak around the water pump area on a 7 series V8, get an early diagnosis. Often the leak appears to be from the water pump itself and many inexperienced shops will replace the water pump only to find the leak is still evident afterwards. The leak stems from a failure in the coolant pipe seals. The pipe runs down the center of the valley in the engine. The seals at the water pump end fail and coolant leaks out of a bleed hole in the water pump assembly. The coolant pipe can only be extracted from the front of the engine, but is too long to be removed with the engine in the car. The BMW dealer usually has this rated as a $6K job. We have a solution for this problem that enables removing and replacing the tube for $1800 and does not require engine removal.
Steering Wheel Vibrates Under Braking
This is very common on the 3 series. Initially, under light braking, the steering wheel will shake. As this problem gets worse the steering wheel will shake more and eventually the actual road wheel will visibly move back and forth under braking. Left alone this problem can cause significant damage. If you catch it at the earlier stage, usually replacing the control arm bushings will resolve the problem. However, left for a longer period, the vibrating can cause ball joint failure on the front end of the control arms and brake rotor warping.
Coolant Leak – 3 Series
The E46 3 series often suffers from a coolant leak near the front of the engine. This is usually caused by the expansion tank. The plastic tank often cracks, possibly due to weather extremes, and leaks coolant. The initial signs are a thin dry line of coolant residue down the side of the expansion tank. Left alone the tank can break open and empty the system rapidly while driving. This causes the engine to overheat and significant damage to occur.
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Check Engine Light – Runs Rough
There are many reasons why a check engine light and rough running could occur. Different models have different common issues. Usually the rough running is a sign of misfires – this is often caused for example, on the V8 engines by a failure of the ignition coils or a collapsing vacumn hose. On the 6 cylinder engines, rough running when the engine is cold can often be caused by a failure in the PCV valve system. This is extremely common in cold weather states and was originally subject to a recall. If left unchecked, the valve can actually pull oil from the sump into the combustion chambers and as in one case we saw, actually oil lock the engine.
Check Engine Light – Runs Great
Very often, a check engine light and a well running engine are a sign of an emissions leak. However, the BMW 6 cylinder engines often suffer from a failure in the intake air boot located between the mass air flow sensor and the throttle body or a failure in the intake flapper valve seal. This allows un-metered air to be drawn into the engine and causes a lean running condition – great for gas mileage, bad for the engine. This may cause extended cranking during engine start up or a no start condition. Idle speed
fluctuations may also be noticed with the engine running.
Blower Motor Will Not Run
This is very common on the older 3 series and 5 series vehicles. The HVAC blower either does not run or runs at 1 speed. The common cause of this is the blower motor resistor which controls the speed at which the blower operates.
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AC Will Not Turn On
See the horror stories section for more information on this example. Sometimes the AC system will not work on a BMW – the compressor switches on for a second or two then shuts the system down. There are a number of possible causes, but one of the most common and seemingly overlooked is a failure in the ambient temp sensor. If the ambient temp sensor has failed and reads a negative F value, the ac system should not operate – why cool air that is already way below freezing!
Check Engine Light – Crankcase Ventilation System
All current BMW engines incorporate a pressure-controlled crankcase ventilation system. The crankcase ventilation systems use various different crankcase ventilation valves, depending on the engine type. Although the valves all look different, they function similarly, using a spring and diaphragm assembly to control the crankcase pressure. A properly functioning pressure control valve is designed to maintain a slight vacuum in the crankcase, which assures reliable crankcase venting during all engine operating conditions. A malfunctioning crankcase ventilation valve may cause the following complaints: Engine runs roughly, Whistling noise from the crankcase ventilation valve, Check engine light on – possible DME faults stored: misfire all cylinders, oxygen sensor/mixture adaptation faults, etc. DME faults stored in the memory will vary, depending on the DME version and the effect of the crankcase pressure for example: mixture adaptation faults, trim faults, etc.
Engine Oil & Coolant Shake – Oil in The Coolant Reservoir?
Commonly wrongly misinterpreted as a head gasket leak, later BMW 6 cylinder engines experience what appears to be overheating and a buildup of oil in the coolant reservoir. This is commonly a result of failure in the oil cooler gaskets causing the engine oil and coolant to mix. When these gaskets fail, engine oil pressure becomes higher than cooling system pressure, causing oil to flow into the cooling system and temp. sensors to misbehave. We recommend replacing the oil cooler gaskets and the coolant reservoir; additionally the cooling system should be thoroughly flushed.
Oil Leak From Alternator Bracket Seal
Seal failure on the alternator bracket is a very common problem with BMW 4.4 V8’s. When the seal fails due to wear and tear oil will leak significantly all over the engine. Importantly, oil will leak into the alternator assembly which could lead to the need to replace this as well. Replacement of the seal requires the removal of several engine components and is quite a difficult and expensive repair. Don’t wait – if you have this problem, you can leak enough oil to do engine damage quite quickly – we can fix this for you today.
Visit Our BMW Repair Shops
Having similar BMW problems? Come visit our Mokena location if you are experiencing any of these BMW related issues. Rennology Motor Sport offers repair, factory scheduled maintenance, and performance tuning for BMW vehicles.