Yep, running a Merc on the sludge we call diesel is bad for the engine

Dear Baraza,

I’m in the process of importing a 2010 Mercedes Benz E250 2.1L diesel from the UK.

It seems most European car makers such as BMW and Mercedes are moving more towards diesel models than petrol ones for their newer models, that is, 2009 and above.

My question is, what do I have to change in the car for it to adapt to the kind of diesel we use in Kenya? Is it true that our diesel is less pure and might cause the car to develop engine problems later on? Andrew

Hi,

The most straightforward way of dealing with this would be to remove the DPF (diesel particulate filter) from the car, but remember, this is a Mercedes-Benz, a brand of car that is thoroughly programmed to the point where it will not start unless the parking brake is engaged; some top-rung models will not move unless the driver’s seat belt is fastened.

It can even tell if you have passengers in the car. What do you think is going to happen when the ECU notices that there is no DPF? Being a Mercedes, the car might even summon the German police (and a breakdown recovery vehicle) by itself, thinking that the DPF has been stolen... (This last part is a joke).

A way around this is to reprogramme the ECU to make it “forget” that there ever was a DPF in the first place. But back to my earlier point: this is a Mercedes-Benz.

Unlike some low-end Japanese models whose ECUs can be hacked into with a simple laptop and RS232 link and software, Benz ECUs are notoriously hard to get around.

Only a few specialists can do this (most of them being German), so for most people looking to mess around with the chip, the best option is an after-market installation.

It’s true our diesel is less pure. A chat last week yielded the theory that the actual situation is “was less purified”; apparently, our diesel has somehow become cleaner over night.

I know it had a sulphur content worse than 500 ppm (parts per million), which is just about as filthy as diesel can get, whereas most diesel-powered cars with DPFs designed to run on Third World diesel are adjusted for a worst-case scenario of 50 ppm.

So our diesel is (or was) 10 times worse than the Europeans actually think it is. It’s like running your car on a gruesome mix of swamp mud, sulphuric acid and just a dash of cooking oil to make it combustible (this last part is also a joke).

The hyperbole in that last statement should make it obvious that running a modern diesel engine on our sludge will be detrimental to your engine in short order.

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Dear Baraza,

Your column is really good. I like the way you write humorously about technical stuff.

Please enlighten me on the car part called the timing belt.

What annoys me is that it gives up the ghost without warning, and the poor car stalls!

The first time I heard that, I asked someone to replace the one in my second-hand car without even checking whether it was due for replacement.

Is there a way of determining when replacement is due? Is this technology not far behind other motoring technological advances? S. Muriithi

Hi,

In most situations, the timing belt does not just “give up”, it suffers a steady degradation, losing tension until the point where all hell breaks loose.

However, cars have ways of preventing this apocalyptic destruction of your engine: either a warning light comes on somewhere in the instrument panel – the warning light, for instance, in the cluster of a Toyota Hiace Shark LH172 is above the speedometer and says “T-BELT– or some cars have self-adjusting timing belts.

These are the type that compensate for the loss of tension by the use of spring-activated pulleys called tensioners.

The spring force acts in the direction perpendicular to the timing belt movement, such that any slack in the timing belt is instantaneously counteracted or compensated for by the spring force.

Yet other engines use gears instead of belts and pulleys. There has also been a resurgence of the chain-and-sprocket set-up in recent times due to increased durability, although chains also suffer from invasion of slack, and tightening has to be done by hand.

Read the manual: Timing belts have manufacturer-recommended replacement intervals, just like other consumables in a motor vehicle. However, sometimes timing belts might not “go the distance”.

A typical symptom of a soon-to-fail timing belt is a rattling noise from the front of the engine.

Physical inspections will also give you clues as to whether or not a timing belt is on the River Styx: Stripped teeth, delamination, unseating/displacement/derailment of the belt within its tensioners and unravelling of the high tensile fibre cores are signs of imminent disaster. Take care of them sooner than immediately.

Fortunately, instances of the belt itself snapping are extremely rare/unheard of; fortunately because if that belt snaps....

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Dear Mr Baraza,

I have a Toyota Mark X 2005 Model. The car has been running smoothly until recently, when it started displaying a battery symbol on the dashboard.

At first I ignored the problem, thinking it was as a result of loose terminals. The problem disappeared after I drove a long distance – about 400km.

The problem has recurred, with other related complications.

Recently, when I was driving to town, the battery symbol appeared on the dashboard and the steering wheel became stiff. After I stopped to check, the car wouldn’t restart I consulted a mechanic, and told me that the battery was low. He replaced it with a used battery and the car moved for about 10km before the problem recurred.

I went back to the mechanic and he suggested that we buy a new battery. He also suggested it could be the alternator overcharging (whatever that means), which meant we needed to replace it.

He also checked the fuses and said they were okay. I am reluctant to heed his advice since he doesn’t seem to be sure what the problem is.

(i)  What could be the problem and is the alternator supposed to overcharge the battery at any point?

(ii)  Will the new battery solve the problem?

(iii)  Is this a problem peculiar to the Toyota Mark X (I have owned two cars before, a Mitsubishi Gallant and Toyota Vista Saloon and I have never encountered such a problem).David.

Hello David,

What you describe here sounds like either the battery is discharging rapidly or, more likely, the alternator is not charging the battery properly – unlike your mechanic’s hypothesis of overcharging.

Did he use a voltmeter to confirm the potential difference across the terminals? Anything above 13.6V p.d is a sure-fire sign of overcharging.

11V is mostly okay (but still a sign of alarm), but anything below that means the battery is discharging.

Whatever the case, the alternator can be repaired or replaced: the course of action will depend on the its design. Also, a thorough check of the electrical system might help determine the source of the alternator’s infidelities. So:

i) The problem sounds like the alternator is not charging the battery. Overcharging could also be a cause, seeing how this leads to battery damage, but failure is not as fast as you describe (within 10km of driving). No, the alternator is not supposed to overcharge the battery at any one point.

ii) The new battery will cure the symptom, only briefly, but will not solve the problem.

iii) I don’t think so. Yours is the first case I have heard of concerning a Mark X with battery problems, but how many Mark Xs are there out there?

There could be other undocumented instances. I, too, suffered something similar back when I was the long-suffering owner-operator of a Peugeot 405 SR, though in my case the alternator was overcharging the battery (as confirmed by a voltmeter reading of 15.1V potential difference).

The car ran fine but the battery light on the dashboard was scary to look at, and I drove everywhere in a state of near-panic, expecting a shower of battery acid to pour on me from an exploded accumulator any minute.

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Hi Baraza,

Great work you are doing. Keep it up!

I drive a 5-speed manual transmission 1998 Toyota Rav4, which I recently upgraded to from my beloved but ageing Toyota Sprinter Carib.

The Rav4 is great. I’ve had it for about a year now and so far, so good, save for two issues, which I hope you can at least demystify, or advise me how to go about:

1. Whenever I have to do multiple start-stop hill starts or in traffic, sometimes I hear some noise from the car’s undercarriage, a banging-like sound, as I release the clutch.

This noise is not always there, and it goes away once the car takes off. My mechanic thinks it is the car’s clutch system that’s about to give, the pressure plate to be specific.

However, I have no clutch problems so I haven’t done any repairs yet. Please tell me what I need to have checked before doing any expensive repairs based on speculation.

The car is serviced regularly and on time, including checking the transmission oil.2. I have noticed with great concern that lately, the car’s rpms are very high at relatively low speeds.

For instance, at 100kp/h the rpm is 3,000. At 120-130kp/h, it goes up to almost 4,000. I find this rather abnormal, or is it not?

PS: I bought the car with a new engine, and all the documentation was in order and its fuel consumption is good. I have no major issues with it

Munene

Hello,

Did the mechanic take a look at the clutch system? Remote diagnosis, while helping narrow down the source of a problem, can never fully identify what the issue is.

1. The problem could be with an engine mount, since you say the engine was new when you bought it. I guess you meant a replacement engine. The issue could also be with the release bearing, or the pressure plate, or maybe even with the hydraulics, which causes the release fork to move too fast and engage the plates with a bang.

For a car nut like yours truly, I’d let the problem develop a bit more to help me further isolate the possible causes, but this is at the risk of spending some hours by the roadside waiting for help should a substantial failure occur (and expensive repairs, subsequently).

The only way for now is a proper diagnosis, i.e., removal of the gearbox and physical inspection of the clutch kit. If the problem lies anywhere there, then it is just as well, because you would have had to remove the gearbox anyway.

2. This doesn’t sound abnormal to me. What gear are you in when doing those engine speeds (and road speeds)? Simple math: 4,000rpm -3,000rpm = 1000rpm. Also, 130 km/h - 100 km/h = 30 km/h. So whatever gear you are in is good for 30 km/h per 1,000 rpm, which sounds like top (5th) gear for most cars.

A simple confirmation is this: the car should be good for about 180 km/h or thereabouts in top gear, right? And being a typical Japanese petrol engine, the red line should be somewhere between 6,000-6,500 rpm, right? So 30 km/h per 1,000rpm X 6,500rpm gives.... 195 km/h, which should be just about right for a RAV4. See? Nothing wrong here, especially since my calculations are based on a clutch that is not slipping. If your pressure plate is dying, then there could be some slip.

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