Help for a Toyota Ipsum that needs to cool down before it starts

Wednesday March 18 2020

The battery. Nothing confounds humanity like understanding the exact nature of electricity, not even the physicists who study it. PHOTO | COURTESY



I hope this mail finds you well. I have a Toyota Ipsum engine model 2AZ FE. Lately, I have discovered that when I switch off the engine after a long-distance drive, it won't start until I have given it some time to cool down. I have even bought another starter motor but the problem persists. The mechanic who replaced the starter motor advised me to check the cut-out or alarm system.

What do you think?

Regards, Mathenge

Hi Mathenge,

This type of behaviour usually comes from one of two causes, both related to heat. Either the heat causes an ageing electrical component to fail - with the thermal expansion properties of materials and increase of resistance in a circuit usually acting as accomplices - or the battery itself is old, so when it gets warmed up it loses its ability to provide sufficient current to drive the starter motor.

You say you replaced the starter motor, so that liberates that particular suspect for now, though I wouldn’t let it out of the precinct doors yet. But first, we list a few other suspects on the electrical component blacklist: check your terminal connections. Not just the nipples on the accumulator (check these anyway, just to be sure), look at the earth terminal on the starter motor and the connection to the starter motor itself. These could be old, frayed and susceptible to failure from heating up. Check the fusible link as well (any point in the starting circuit with an inline fuse). Then there are the crank position sensor and the ignition control module. If the crank sensor is at fault, it usually results in a Check Engine light, mostly. The control module does not cause a light. Check both anyway just to be sure, but keep in mind neither is cheap to replace.

The battery. Nothing confounds humanity like understanding the exact nature of electricity, not even the physicists who study it. I know this because I have a degree in physics and part of the studies involved electrodynamics, yet 15 years down the line, I still wonder what on earth was going on in those lecture theatres. James May himself, of “Top Gear” fame, concedes that nobody fully understands how electricity works. It is on this line of thought that I present my next argument: the heat from driving would cause an old battery’s performance to flag. Other people who think they understand electricity will argue that cold is what causes a battery’s performance to flag, warm batteries behave better. Hardly so. Listen here.

There is battery capability and battery life. One is the power output of the battery. The other is how long the battery delivers this power. Heat affects battery power, and if you supply enough of it to the battery, it will go boom. The folks behind the Samsung Galaxy Note 7 smartphone dislike this paragraph, and this is also why it is not advisable to store your phone or tablet underneath your pillow while it’s charging.

Cold, on the other hand, causes a battery to drain faster, but it will not lower its “power” or outright capability.

That means that an old or poorly thermo-insulated battery will lose its ability to give current when exposed to heat, which means there isn’t enough “fire” (sorry) to turn the starter until things cool down somewhat. The explanation behind this is fairly straightforward and has already been mentioned in the first paragraph: heat in an electrical circuit increases resistance in that circuit. 

This includes the battery itself, via what we call internal series resistance. This is the natural resistance of the battery (all materials have electrical resistance at one level or another; those with very low resistance are called conductors.) 

Those with very high resistance are called insulators and it increases with age and with heat. In what can only be described as a vicious cycle, high resistance in a circuit causes heat to increase in that circuit, which in turn increases the resistance further... until your Samsung Galaxy is subjected to a recall.

So there you have it. A, B, C, D, P, G, C: X to the Z. Don't buy any other starter motors (yet). I don’t think the accumulator in your bonnet is the culprit here, but start by experimenting with a replacement battery. If it changes nothing, now start tinkering with the wires in the engine. 

Things like the aforementioned fusible links can be very difficult to get to. If these seem legit, now look at the pricey stuff: the crank sensor and the ignition module. I'm not so sure about the cut-out and/or alarm system, but strange things are known to happen and they are possible suspects, if not plausible or probable.

What is this oppressive heat likely to do to my Subaru Forester?

Mr Barasa,

I am an adherent reader of your very informative column. I am also a motoring enthusiast and a petrol head. I live in a country where at times daytime temperatures are shy of 50 degrees for an average of eight months a year. I drive a Subaru Forester 2007 model, non turbo. I park in uncovered parking slots, therefore my car is exposed to the heat all day.

1. What are the effects of such exposure to the car’s performance, other than the normal wear and tear, especially on the paintwork.

2. What is the relationship between the Subaru Box engine and the asymmetrical car balance and how does it affect its handling and stability.

Richie P,  Dubai

Hi Richard of Dubai,

I do not envy you stewing in that kiln of a country, haha. I hope the stay there is worth the poaching you undergo. Anyway:

1. The vehicle is not turbocharged so the ambient temperature won't affect performance drastically. Turbocharged (and supercharged) cars need intercoolers because the heat from compressing the intake charge causes it to lose density which is the exact opposite of wanting to compress it in the first place. The compression also raises the temperatures so high, there is a risk of pre-ignition, hence the intervention of the intercoolers, heat exchangers that calm things down a little.

But your car doesn't have forced induction so it doesn't need an intercooler, and 50 degrees is not so high as to cause pre-ignition since the temperatures the air reaches during the second stroke of the four-stroke cycle is far above that. As for air density... correct me if I'm wrong, but I do believe Dubai is at or near sea level so atmospheric pressure keeps the air nice and dense enough despite the geographical oven being set to 50degC for eight months at a time.

So to wrap this up... no effects. Your Forester is fine as far as performance being affected by climatic conditions is concerned.

2. The boxer engine is flat and mounted low in the car, so that lowers both the centre of gravity and the centre of mass, leading to a more stable vehicle. Most longitudinally-mounted inline engines (and some Vee engines) are canted over to the side ever so slightly to make them fit inside the bonnet or else you end up with a very tall or very wide bonnet. This throws the balance off. As for transverse engines, besides the canting over, they are also unbalanced by design. On one end of the engine is the clutch and flywheel, a very heavy combination that is not there on the other side, to put it empirically. This gives the vehicle a lopsided weight bias which requires some clever chicanery to counteract, but it is still there. The boxer engine on the other hand is centrally located, placed upright and longitudinally mounted, so weight distribution is even.

Then there is the bane of the powerful front-drive car: torque steer. Torque is the twist action from an engine, and it is defined by a force working over a certain distance. We have the clutch and flywheel at one end of the transverse engine, possibly in the form of a transaxle if the gearbox is part of that mess. Then we have nothing on this other end. However, power has to be delivered across the entire axle, not just to one side. The result is the side with the transaxle will get a very short half-shaft (the rod that translates the rotational motion from the differential to the wheel hub) while the side with nothing requires a very long half-shaft extending from the opposite side.

Remember torque is a force acting over a distance. The force from the engine through the gearbox is the same one, but the torque reaching either end of the axle is not the same. That constant force is acting over variable distances, which means one wheel will actually receive more torque than the other, which is what leads to torque steer.

What is torque steer? Get into a suitably powered front-drive car, point the wheels straight, let go of the steering wheel and floor it. It will take off normally at first, then as it approaches the point of maximum torque within the rev range, it will pull violently to one side. Do not adjust your suspension, that is torque steer.

Now, Subarus don't suffer from this, again because the longitudinal mounting of the perfectly weight-distributed engine across the pitch axis means there is no weight bias on either side. Then the engine, gearbox and diffs are all mounted in a straight line along the roll axis, meaning the half shafts are of equal length on both axles, which in turn means torque steer only arises if you happen to sneeze very hard (gesundheit!) when in the middle of proving a point to a doubting Thomas.

This right here is summary of the much vaunted Subaru Symmetrical All-Wheel Drive System. It all boils down to balance.

Baraza, you know nothing about motorcycles…

Baraza, please, you’re hurting the feelings of motorcycle fans here. There are good bargains in the showroom, you can get a good superbike for Sh500,000 up to Sh1000,000. I don’t think you are an expert on motor bikes. If so, please avoid commenting on them.

Hi Alexander,

I have never claimed to be an expert on motorcycles. In fact, each time the topic arises, I specifically confess that my knowledge on these hateful things is limited - but it is not nonexistent, let's be clear on this. I can discuss reed valves, chain drives and the pitfalls of installing ABS in bipeds as well as any grownup with a leather jumpsuit and a subconscious death wish can.

I don't really care much about the pricing of bikes either, but I know you can get a brand new one for less than what I make per month. Sure, it will have fewer CCs than an espresso cup, but my point still holds. I also know you can get a used bike for more than the combined value of all my cars, in which case my other point is made: monetary worth is not really that high up. Why would I buy a 2014 Lauge Jensen Great Dane Kahn No. 3 at $64,000 only for someone to mistake it for a $10,000 bike and quip "Nice Harley-Davidson"?

So, really, thanks for the update on bike pricing, but next time, attach a few names to your price tags so that we can have something I like to call "perspective". Which are these 500k iron goats and which are these million-shilling glorified scooters? I cannot avoid commenting on bikes because 1. they fall under motoring, of which I am a key local and global component and 2. if I'm asked a question, I will answer it, even if the answer is "I don't know but I can hazard a guess".

Did you say my disregard for motorcycles hurt your feelings? I bet it is less painful than sailing over the handlebars whenever you need to make an emergency stop. I will appropriate a quote from one of Eric Blair's better known works and adapt it for use in this context: four wheels good, two wheels bad.

See you next week.​