Knocking sound and loose dipstick

I DRIVE a Toyota Yaris sedan that has done 149000km. It has been serviced regularly every 15000km at a Toyota dealer. The 150000km service was done a fortnight ago.

About 500km later I began to hear a knocking sound coming from the right-hand side of the car when I turn the steering wheel to the left.

When I drive straight or turn to the right, there's no noise.

What do you think the problem is?


I know I always warn against snap diagnoses, but here I am going to stick my neck out and say it's almost certainly a worn CV joint on the right-hand sideshaft. Each sideshaft on a front wheel drive vehicle has two Constant Velocity joints, one at each end.

The outer one, situated where the sideshaft connects to the wheel hub, has a harder life than the inner one, because it has to allow the wheel to swivel through quite large angles for steering purposes.

It is common for the outer joints to wear out long before the inner ones, and I suspect you are hearing the distress call of the right outer joint. Its twin on the left side is sure to follow suit in the near future, so both outers will have to be renewed.

At the same time you will have the opportunity to examine the inner joints for early signs of wear.

Make very sure that the replacement joints fitted are new ones made by a reputable manufacturer.

It might be wise to insist on genuine Toyota parts.

Reconditioned joints, or exchange sideshafts that will probably have reconditioned joints on them, are to be avoided, no matter how attractive the price.

Have a good look at the old joints to see what has caused the wear on the right one. Premature wear often occurs when the rubber boot around the joint, which is supposed to keep the grease in, and dirt and water out, cracks and splits.

These boots, especially the ones over the outer joints, should be inspected regularly. And if you want to repack a CV joint with fresh grease, be sure to use only special, high-pressure, high temperature grease formulated for CV joints.

Ordinary chassis grease or multipurpose grease is not good enough.

I have a 2002 model Alfa 147 2,0 Selespeed. When I drive at 180kmh the dipstick pops out and oil comes out of the dipstick tube.

Even if I just rev the engine to 6000rpm the oil comes out of the dipstick tube. The engine is not smoking or using oil. Please help!


Vusi, there is little doubt that pressure is building up in the crankcase at higher revs, but the reason why this is happening is less obvious.

If I can explain briefly: In any engine a certain amount of combustion gas escapes past the compression rings during times of peak pressure in the combustion chambers, just after the mixture has ignited.

In a new, properly run-in engine it will be a minuscule amount, but as the compression rings wear the so-called "blow-by" gradually increases.

The gas ends up in the sealed-off space around the spinning crankshaft (the "crankcase") above the oil in the sump. If no outlet is provided for this gas, the pressure in the crankcase will rise to the point where gas, mixed with oil vapour, will force its way out by the way of least resistance, which might well be the dipstick tube.

To prevent this from happening, engines are fitted with a positive crankcase ventilation (or "breather") system that extracts the gas-oil mist mixture from the crankcase, separates the oil mist from the gas, and feeds the gas back into the inlet manifold to go into the combustion chambers again.

When the pcv system is partially blocked, and the compression rings on the pistons are perhaps a bit worn, the breather might be unable to cope with the amount of blow-by, especially at high revs, and you might get crankcase compression, leading to the symptoms that you describe.

I suggest that you begin by cleaning out the entire breather system. It will probably have a one-way valve somewhere along the line and this is often the place where the blockage occurs. Make sure that there are no sharp kinks in the hoses, or pinched hoses which can prevent the free flow of gas.

There's a good chance that your symptoms will disappear temporarily once you have done this, but I am afraid you are going to find that excessive blow-by has been the root cause of the whole problem, which would mean you are looking at new pistons and possibly a rebore job sooner or later.

Just a word of caution: Revving an engine to 6000rpm under no-load conditions (gearbox in neutral) puts enormous stress on certain components, in particular conrods.

On some modern engines the electronic control unit will prevent the revs going much above 2000rpm when there's no load on the engine. I would adopt that as a prudent policy.