Check for worn-out wheel bearing

Q1: A faint clinking sound is coming from the engine of my four-year-old Smart Forfour when the car touches 70kph. The sound will become audible again whenever the accelerator is pressed beyond that speed.. The car still runs smoothly and there is no loss of power. Is this a "knocking sound"? I am filling up the car with RON95 and RON97 alternately. Please enlighten me.

Ricky
Petaling Jaya

Knocking sounds usually occur parallel with engine rpm. In other words, the higher the rpm, the louder the knocking sound. To be sure that the sound came from the engine, seek advice from your technician. Because usually, when the sound becomes audible at a certain speed, it means that the wheel bearing is wearing out.

If it is related to the engine, we recommend that you use RON97 regularly or whichever grade is more suitable for your car.  Refer to the owner's manual. We understand that the Smart Forfour must use premium petrol. Octane rating greatly affects the engine performance and emissions as well.


Q2: I have just changed to a brand new battery for my 1994 BMW 325i. The E36 has clocked nearly 200,000km. The alternator was recently replaced with a used one. The car was running fine for a few weeks but a few days ago, the gearbox and ABS indicators lit up on the instrument panel. The radio was on and seemed to lost signal intermittently, and the power windows was slow in going up as if it did not have enough power. The mechanic checked the battery with a meter and said the wiring could be the problem as the meter was registering 13V instead of 14.

Goalpost
Petaling Jaya

Firstly, ask the technician to test the current output from the alternator to see if it meets specifications. If there’s no problem there, you can then suggest they check the wiring for any grounded leakage or corrosion.

If ground connection is the cause of the problem, remove and clean the ground points and re-install properly.

If the alternator is the source of the problem, you might want to check the carbon brush as it may have already been worn out. This goes for the other component of the alternator as well.

We recommend getting a new alternator.


Q3: I have a 2001 Land Rover Discovery and recently the transmission failed while driving.  The transmission was replaced, but the unit still would not start. The mechanic says we need a code to clear the system that is stuck in theft mode. What do you think?

Landie User
Johor Baru

During diagnosis, when an OBD-II fault occurs in Land Rover's Generic Engine Management System (GEMS), the malfunction Indicator Lamp (MIL) is illuminated. GEMS Diagnostic Trouble Codes (DTC ) are stored in the Engine Control Module (ECM ) and may be retrieved by connecting a suitable OBD II Scan Tool or the Land Rover TestBook Electronic Tester to the Data Link Connector (DLC-3 ). DTC's can only be diagnosed and erased by the TestBook Scan tools, or an appropriate after market equivalent, approved by Land Rover.

The following OBD Trouble code related to the transmission are the following for your reference:

P1 code Specific Fault Code Description       
P1514     Neutral Drive Load Fault       
P1516     Neutral Drive Gear Change Fault       
P1517     Neutral Drive Cranking Fault      
P1775    Gearbox Fault      
P1776    Gearbox Ignition Retard Request Timeout Fault      
P1777    Gearbox Ignition Retard Request Line Fault      

All information regarding DTC's for this model is contained within the Land Rover TestBook Diagnostic Unit.
As you can see, the trouble codes are NOT “generic” at all. The number “5” after “P1” signifies that the affected system has to do with vehicle speed/idle control and auxiliary inputs, whereas “7” signifies that the gearbox components is affected. The last two numbers specifies the exact problem as shown in the description of the code above.
 
If in doubt, consult any Land Rover Authorised service centre for you to avail the proper diagnostic tools as mentioned above and to verify the problem.