Ask the mechanic: Why does my Benz have a persistent ABS fault?

Hi Paul, I drive a Mercedes Benz ML 320 model 2000 and it has been a reliable car so far. Lately it has developed a persistent ABS ETC fault. The fault lights display on the dash board and when I brake, the pedal rumbles intermittently. A mechanic has advised me to replace the ABS pump which is likely to have failed. The cost of this part is horrendous and I would like a second opinion before I commit. What should I do? Jonathan.

Hello Jonathan, the Anti-Locking Brake system (ABS) on your Mercedes is designed to work with other components or control modules under the ESP - Electronic Stability Programme. This integrated system includes the engine control module, TC - Traction control module, instrument clustre module, transmission and transfer case module, etc. These systems are linked by an automotive high speed data transfer hub or network called CAN BUS.
A break down at any point of this network will be picked up by all the control units on the network as such anyone of them may seem to be faulty.
Before you write off or attempt to replace the ABS modulator, it is prudent that you find a good Mercedes technician who will follow test steps to test the CAN BUS network and isolate where the faulty component is.
Whilst the ABS controller is susceptible to damage from a leaking window washer reservoir, sometimes the fault you describe can be caused by the ETC control module.
A correct diagnosis is necessary to avoid buying the wrong part.

Hi Paul, I drove on a road with tar. I later noticed that the lower white paint around my car was soiled with black tar. When washing, we tried as much as we could but failed to washit off. How can I wash it off?
John

Hello John, road tar can be a public nuisance when it sticks to your car paint. Even plain soap may not be as successful with removal of tar. My advice is that wash the car thoroughly and as you dry it use some kerosene (parafin) to remove the tar stains as you clean with another clean cloth dipped in a mild detergent. Thereafter rinse with water. That will solve the tar problem.

Why does my engine oil run out so fast?

Hi Paul, whenever I check, the oil level of my Toyota Corona ST190 is always low and the car produces a lot of smoke whenever I switch on the engine. Sometimes the accelerator gauge on the dashboard is not relative to the speed when I am driving. It also rises even though I am not accelerating, on a slope braking may be 80km/hr it will show me 4 (x1000r/min) if the gear selector is on drive mode. What could be the problem?
Joseph Kakiga

Hello Joseph, your Toyota Corona ST190 seems to have two engine faults. The first fault or condition is engine oil loss. From what you describe, your engine burns more oil than it ordinarily should. Every engine will burn a very tiny amount of oil during combustion that will amount to less than half a litre after 5,000 kms for older vehicles like yours.
However, when oil burnt exceeds one to two litres over a 5,000 km service interval or even shorter periods, it means the engine has damaged piston rings and is leaking a lot of oil into the combustion chamber.
This is confirmed by blue smoke and a drastic reduction of engine oil quantity in a shorter spell. This will call for an engine overhaul or replacement of piston rings and crankshaft bearings after dismantling inspection of the engine to determine the extent of repair needed.
The erratic movement of your engine revolution counter or rev meter suggests that there is a problem with your engine throttle potentiometer or idle air control valve. This is the unit which controls air intake to the engine combustion system. Air intake enables acceleration or idling. When the throttle potentiometer or the attached idling air control valve are dirty or clogged with deposits the throttle valve could get stuck hence causing erratic acceleration even when you are not stepping on the gas (accelerator) pedal. A qualified technician should dismantle and inspect or service this unit so as to fix the problem.

Ask the mechanic - By Paul Kaganzi (0772316145)