Misbehaving tyres, misinformed mechanics and, well…

Hello Baraza,

I want to pick your brains on a couple of things:

1. Yana tyres: I recently replaced my tyres, one pair Yana and the other Chinese Marshall. The car started “bouncing” whenever I was at about 40kph.

After checking, I zeroed in on one of the Yanas. On closer observation, however, we noticed that the rim was slightly bent and required to be straightened (well, that should be rounded, no?)

At the workshop, which is independent and specialises in tyre service but not sales, the very experienced mzee said that the quality of Yanas has gone down and that he would not recommend them for saloon vehicles, although he admitted that their durability is still good.

He said that they were too “heavy” and therefore require frequent balancing, and suggested that I fit the Yanas at the back.

After fixing the rim, the problem persisted and I went back to Sameer. To their credit, they replaced it without much fuss.

At the workshop where we took the new tyre for balancing (at an independent Shell station where they do not sell tyres either) two different gentlemen there also commented about the “lowered quality” of Yanas.

When I asked the engineer at Sameer about this, he said that it was all hogwash, but probably he would not have said otherwise even if it was true.

In all my years of driving — heading to two decades now — I have always thought highly of and hence used Firestone, now Yana, and considered them good value, even with their high price.

But having heard the comments from two independent sources, neither of whom sells tyres, and therefore should not have a personal interest, I fear that there could be something there. What is your experience/opinion?

2. Clearance: When it comes to offroaders, I believe that clearance is key in enabling you to go wherever your heart leads. But your clearance is only as good as the vehicle’s lowest point.

So does it not beat the purpose when, say, an X-Trail has a silencer hanging what looks like inches off the ground, or some 4WD pickups that have differentials dangling like udders?

3. Many experienced drivers say that when you are going a long distance (say, several hours long) and have to make a brief stop in between, you should not switch off the engine.

Although they all seem to agree on this, none has given me a convincing reason.

Some say it is to maintain the temperature (but will five to 10 minutes make a difference really?) others lubrication (ditto), and one even said that when switched off, an engine loses “rhythm” (but he drives a petrol-powered VVT-i whose “rhythm”’ should be controlled by the computer-box).

Does this make any sense?

4. I have been doing some agriculture and now would like to take it a notch higher.

One of the things that I will need is a tractor. I have seen used entry-level imports being advertised and some locally used ones as well and have started taking a look at some.

But unfortunately, the only advice I am getting so far is from sellers/dealers who are, predictably, biased.

What is your experience in terms of the different models (assuming equivalent specs): Ford, Massey Ferguson, Same, New Holland, John Deere, etc in terms of local availability of spares and expertise, reliability, etc?

Tom

Well, you are not the first to mention the Yana issue to me. However, I usually reserve judgment until I come up with conclusive evidence (myself). This might call for a comparison test between tyre brands to see who the culprits are.

2. Yes, that is true, and that is the likely reason the X-Trail with the “udder” exhaust is never taken off-road.

However, the bigger SUVs with the “udder” diffs work well. Off-roading is a skill, and part of that skill is how to avoid knocking out those diffs when driving over a rock or a tree stump.

If you have been following events of late, I was in South Africa (again) recently to drive the little Range Rover Evoque off-road, and you would not believe what it did, even with its (lack of) ground clearance.

It boils down to skill as much as ground clearance.

3. The theory about losing “rhythm” is hogwash, but there is sense in leaving the engine running if your stop is going to last less than five minutes.

The biggest problem is the sudden loss of oil pressure, so if you are going to drive off again, you would not want an oil-less engine to work with (start lubricating from scratch).

Heat dumping is another issue: while oil is used to lubricate, it is also used to cool certain parts of the engine.

With the oil pump not delivering oil to those parts, they cannot cool fast enough and so they “dump” the heat in whatever little oil happens to be around there.

If the dumped heat exceeds the heat capacity of the oil there, the oil is coked, or broken down, so you have no oil, but sludge. This heat dumping is the number one killer of turbochargers, especially in diesel engines.

4. I will have to disappoint you on this one. The last tractor I was involved with was a Ford Hughes 6610, and it was older than I am. I have not had much experience since.

Hi Baraza,

I am an ardent reader of your articles. Please give me some advice on what I can do about my Toyota Wish.

I refuelled at a Shell petrol station in Machakos and a pump attendant messed up by pumping diesel into it instead of V-Power, as I had advised him.

They later emptied the tank by disconnecting the fuel pipes and off I went. The car is new and I request you to advise me on what I can to do to clear the mess.

Second, what is your take on this car? I have never heard you comment positively about it. You once equated this expensive car with a bicycle and my fiancée now tells me that I drive a cheap car.

James.

Disconnect the fuel lines, empty your petrol tank, and rinse it out with petrol.

As for the fuel lines and the filters/injectors/pumps, you may need someone who is knowledgeable in the exact workings of a Wish.

A common method of cleaning out wrongly fed vehicles used to be to disconnect the fuel filter from the injectors, then prime the pump until only petrol is coming out through the filter. Then reconnect the throttle body to the filter and crank your engine.

Baraza,

Thanks for the good work you are doing. I want to engage you on a new-found love in the Mazda RX8.

From the little knowledge I have gathered, the RX8 is a 1300cc and does not have pistons. Here are my queries;

Is there a garage you know that services other types of engines that are not piston-driven?

What is the biggest weakness of these types of engines?

Would you buy this car?

How is the fuel consumption?

Which other vehicle would be ideal as a sports car?

Rick

The “non-piston” engine in the RX-8 is actually called a Wankel.

To differentiate them, let us use their proper names: Piston engines are called reciprocating engines because the pistons move in an up-and-down (reciprocating) motion.

The Wankel engine is called a rotary engine because, one, rather than conventional pistons, it uses rotors (usually two or three) and these rotors move in a circular/rotating motion, hence the name.

I cannot declare any one garage competent enough to service these engines because they are rare and delicate.

If one garage proves its mettle, I will be glad to get their name out there.

There is very little torque, they require regular servicing, the oil consumption is high and they are thirsty. The rotor tips also get fried very often, requiring frequent overhauls.

See 2 above.

No, and for the reasons, see 1 and 2 above. There are also very few around, so spares and replacement engines may be hard to come by.

This is compounded by the fact that the Mazda unit is the only automotive engine of its kind in recent times and it is no longer in production.

When getting one, the best thing to do is a compression test to see if the rotor tips need replacement (replacement means overhaul, by the way).

There are many sports cars. Keep looking.

Hello Baraza,

Kindly advise me on the effect of keeping your foot on the brake pedal in an automatic transmission car as opposed to engaging the neutral gear for those short start-stop moves, especially in traffic jams.

Also, where can one read and keep abreast of traffic rules and their relevant actions or fines since policemen frequently take advantage of our profound ignorance even for trivial issues such as a cracked windscreen or failing to carry your a driver’s licence.

Ndung’u.

The only effect of keeping your foot on the brake pedal is a tired calf muscle from applying pressure on the pedal all the time. That is it. It does not hurt the car at all.

On traffic rules, I think a regular subscription to the Kenya Gazette would be a good source of updates on rules and regulations, because the ones we see on TV are not always very well explained.

However, I can tell you from experience: you will never win an argument against a traffic policeman. If he decides to take things a step further, knowing full well that he has no case, he has nothing to lose.

You, on the other hand, will be inconvenienced thoroughly if your car is impounded or you are given a court summons.

Hello Baraza,

I have a Toyota Duet fitted with a manual gearbox and for a while it has given me problems to the extent that I have grounded it.

The problem started two months ago while I was on my way to Thika. The car started intermittently jerking then running smoothly before it stalled.

My mechanic came, checked the engine, and said that I should buy a new head gasket to check the leaking oil, but even after we installed it, the engine would not run well.

After a lot of guesswork, during which he removed the timing belt but could not re-instal it, he finally told me that probably the car needs new piston rings and a lot of blah blah blah.

Kindly advise me on whether there is someone out there who can return the duet’s timing belt to its proper position, and what is required to put the car back on the road.

Tony

My deepest sympathies for your woes Tony, and for being at the mercy of a clown of a mechanic.

The jerking, I suspect, comes from an erratic electrical current in the high tension leads. The leaking oil may or may not be a contributing factor.

My advice is for you to visit a reputable garage. Since I cannot market particular enterprises, all I will say is find a big one, preferably one referenced by a friend.

Dear Baraza,

What are the advantages of the VVT-i engines in Toyota cars in terms of safety, speed, fuel consumption, and manoeuvrability on both tarmac and tracks in rural Kenya? These cars also come in automatic transmission trims.

J B Angote.

The transmission type is largely irrelevant when considering the pros and cons of VVT-i, but anyway here goes:

Safety: The use of variable valve timing has no direct effect on vehicle safety, but the engine management could utilise this variable timing to dial back the power in conjunction with the traction control system.

Speed: If by speed you mean outright performance, then yes, VVT-i does help. In the low rev range, say 4,000 rpm and below, the valve timing and lift is programmed for economy and smoothness.

At higher revs, towards the red line, the engine management assumes a racer-type personality and adjusts the valve action accordingly.

In some engines, this is achieved by the use of two different camshafts, or a camshaft with two profiles, one for economy and one for performance. Honda’s equivalent of VVT-i is called VTEC, and in some cars (such as the Type R vehicles), one can actually feel the change-over taking place as you drive along.

Fuel consumption: Same as speed above, but this now happens at low revs. At low engine speeds, the valve timing and lift is set for optimum economy (and thus poor performance).

Manoeuvrability: This has more to do with suspension and chassis setup than engine management.

Hello JM,

Many thanks for enlightening us through your insightful articles. I enjoy reading them every Wednesday and have picked loads of tips.

I was very eager to read your responses regarding issues that one of the writers had about his/her AE 111 (1,600CC). I have a similar experience with my Caldina 1,800CC, 1993, manual transmission model.

1. At a speed of 40KPH, the vehicle shakes/vibrates so much, it feels like a person limping while running. Several theories have been fronted by mechanics who unfortunately have failed to diagnose the problem.

Some say it has to do with the Yana tyres I bought recently — two of which I bought early last year and the other two in 2010, and all of which are in fairly good shape.

Others have recommended wheel balancing and alignment, which I have done several times without any success.

I am at my wits end and considering replacing all the shocks soon to see if that is where the problem lies. I have replaced tie rod ends, stabilisers… name it.

There is also a light on the dashboard that usually comes on when one of the brake lights is not functioning. Despite replacing the bulbs, this light is on. What would you advise on this?

Lastly, I intend to buy a new car soon and am considering buying a Toyota Alphard. Are there manual types? Any pros and cons you may wish to share?

KO

That Yana tyres issue has arisen several times in the recent past from different readers, but I am avoiding it for now. Without solid evidence, I cannot comment on it yet.

I expect that the manufacturers, after reading this, will be in a position to reaffirm the superiority of their brand, which, as one reader says here, has been top-notch for decades.

I am, however, compiling a list of repeat offenders and planning on putting their products to the test to verify whether or not they are indeed below standard.

As for the vibration, if wheel balancing and alignment does not solve the problem, tell the mechanics to look at the wheel bearings.

They might have gone out of round or suffered some other physical affliction and need replacement. One of the cars I drive has exactly that problem.

On the brakes issue, what light is that? The dashboard has a variety of lights and graphics.

Finally, I know not of any manual transmission Alphards. The car is smooth, comfortable, fancy, handy for large families and if only Toyota’s G-BOOK telematics software worked here, it would be really awesome.

Its cons are; Toyota’s G-BOOK telematics does not work in Kenya (Japan only), the car is expensive and a 3,000cc V6 petrol engine powering a large van means one thing: thirst.

Hello,

Your educative motor articles on Wednesday are a must-read for me. I drive a Toyota Probox, 2005 Model (NCP 51V).

I have been using it for a year and was its first user in Kenya. Problem is, the starter needs to be cranked twice for it to start running, but in the morning it starts well, albeit with a “choking” feel.

Once the car starts, it picks properly and has enough power. I have taken it to five mechanics and all have given me varying verdicts.

The first one argued that we needed to change from Denso to NGK plugs, but this did not help the situation at all.

The second one had his finger on the alarm system, but the installer said it was okay. I did a diagnosis that returned a low/high voltage verdict, but the battery technicians at Chloride Exide said all was well with the battery.

The third mechanic argued that the fuel pump was delaying delivery of fuel to the engine, but after cleaning it I noticed no change. The fourth said the throttle was clogged… same story.

The fifth one, thank God, was clueless.

Help!

Peter

Let us go back to the second mechanic because it seems he came closest to locating the problem.

The diagnosis said wrong voltage, right? Too high or too low. The battery and charging systems might be fine, but what about the high tension leads? The ignition system?

Check the distributor and the alternator, as well as the cables themselves. Also check the ignition coil and make sure the starter motor is getting enough electricity.

Check for loose or frayed connections which could lead to sporadic shorting.

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