Steering system: Why does my engine fan make noise when I start the car?

Hi Paul,
I drive a BMW X6 3.5 petrol. It has developed a strange fault lately. When I start the car, the engine fan starts to run fast and makes a loud noise. We can’t figure out why this is happening. Advise what we should check. Andrew.

Hi Andrew, the engine blower fan is controlled by an automated system actuated by a control module which is linked to the main engine control module. This engine blower fan performance is regulated by changing engine temperature and coolant flow conditions.

There are engine temperature and coolant pressure sensors which keep updating the engine control module (ECM) with changing conditions. The ECM will determine the blower fan speeds according to the changing values communicated by the coolant temperature and pressure sensors.

The performance of the blower fan is therefore affected by the operation of the thermostat and engine coolant water pump. In the event that one or both of these components fail, the engine computer will activate emergency running.

This is designed to keep the engine extra cooled under the assumption that engine coolant is not flowing as it should. You must get a qualified BMW technician to run a computer diagnosis which should confirm my hunch that the thermostat or coolant pump or both have failed.

Hi Paul,
I have a 2001 RAV4 that has done 200,000 kms and reasonably maintained. At high speeds on the highway after 10 minutes or more (70kmh and above), the temperature gauge slowly starts dropping that it is almost near Cold, at slower speeds, traffic jam or going over humps it goes back up to medium (the optimal temperature). It does not go above optimum. Is this a normal situation or something for me to worry about please advise? Regards, Trevor

Hello Trevor, you may need a good mechanic or car electrician to investigate the performance of your RAV4 engine’s ECT sensor (coolant temperature switch or sensor). The ECT sensor is a thermistor switch which is designed to send different electrical impulses with changing temperature.

This will be relayed to the engine computer which in turn relays it to the temperature gauge and the engine cooling fan system.

As you drive along the temperature of the engine rises to the normal operating temperature which is about 80 degrees centigrade. When the temperature exceeds 80 degrees the fan speed usually increases as the thermostat opens to allow cooler water to flow into the engine and bring the temperature back to 80 degrees or just below. So the temperature gauge should drop or rise consistently and not erratically it as it is doing.

Once the ECT sensor is checked and found faulty it should be replaced.

Should it be found okay then investigate the circuit between the ECT sensor and engine computer or the engine temperature gauge. A computer diagnostic tool will shorten the investigation time.
Hi Paul,
I have a Subaru Legacy B4 model 2004, 2.0 with k25 power but sometimes I park it very well after some few minutes when you try to start, it fails and all the system goes off completely but after another trial it starts. What could be the problem with it? Martin. M

Hello Martin, your Subaru’s erratic start failure may be a result of an electrical fault. The range of possibilities is wide and definitely requires inspection or computor diagnosis rather than a remote diagnosis.

The symptom you describe will require a good car repair technician to check power supply from the battery including the the terminals. The starter system and fuel supply, its connections and relay should be inspected for loose connections which cause the intermittent failure to crank.

Hi Paul,
I drive a Honda Fit GD1. However, my mechanic claims its losing power because I put fake Hydraulic. Just wondering does the Honda Fit GD1 need special type of hydraulic. Edwin.

Hello Edwin, your Honda Fit GD1 has a CVT automatic gearbox. CVT stands for Continuously Variable Transmission or Constant Velocity Transmission.

This type of automatic transmission provides more useable power, better fuel economy and a smoother driving experience than a traditional automatic transmission.

Gears are shifted in a manner that matches the appropriate ratio for a particular driving situation.

The lowest gears are allocated to setting off, mid range gears for acceleration and passing, while higher range gears are for fuel-efficient cruising. New users of the CVT automatic transmissions in recently introduced vehicles like Honda FIT, Honda Jazz and HRV like yours will need to understand that CVT gearboxes sound and operate differently when compared with conventional automatic gearboxes.

In some of them when you step hard on the accelerator, the engine races as it would with a slipping clutch or a failing automatic transmission. This is normal as the CVT adjusts the engine speed to provide optimal power for acceleration.

Some CVTs are programmed to change ratios in steps, so that they feel more like a conventional automatic transmission. That said it is important to know that CVT transmissions use special CVT oil. Different car manufacturers recommend different grades (viscosity) of CVT oil so consult your user manual or check online.

Do not attempt to service this gearbox with generic transmission oils designed for the conventional gearbox, this will make the gearbox fail. In the absence of a Honda dealer you need to find the correct CVT oil online or ask your mechanic to help guide you. With the correct oil you could service the gearbox and observe how it performs before drawing conclusions.

Ask the mechanic / By Paul Kaganzi (0772316145), send sms: mycar (space) your comments and questions to 6933, or email them to [email protected]


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