The 2.4-litre 4B12 was fitted to Mitsubishi crossovers and saloons and belongs to the family with automatic valve clearance compensation. That automation runs on engine oil, and as soon as the oil stops meeting the requirements the mechanism starts speaking up. The owner hears it as ticking or rapid tapping from the top of the engine. Here is where the sound comes from, how to tell it from the others, and what a workshop does.
How a hydraulic lifter works and why it ticks
A hydraulic lifter is a small cylinder that uses oil pressure to take up the clearance between the camshaft lobe and the valve. While there is oil inside and the pressure is right, there is no clearance and the mechanism runs silently. If oil does not arrive in time, or drains out of the lifter overnight, a clearance appears — and the lobe strikes the follower. The result is a rapid sharp ticking from the top of the engine, audible at idle.
There are not many reasons why oil fails to arrive: contaminated passages, a worn lifter, a low oil level, oil that is too thick or past its life. A mechanical failure is the exception here — in most cases the problem starts with the lubrication.
How it sounds and how it differs
| Sound | Source | Distinguishing feature |
|---|---|---|
| Rapid ticking from above | Hydraulic lifters | Quickens with revs, ignores load |
| Rustle at the front of the engine | Chain and tensioner | Heard at start-up, from the timing drive |
| Dull knock from below | Big-end bearings | Grows under load, lower in pitch |
| Injector clicking | Fuel system | Even, unchanged with warm-up |
| Whistle or whine | Accessories | Disappears with the belt removed |
The main clue is frequency: lifter ticking rises with the revs because the lobes strike more often. Bearing knock, by contrast, responds to load — see signs of big-end bearing knock. The general breakdown of this group of sounds is on the symptom page knocking in the engine, and the checks for lifters themselves are in how to check hydraulic lifters.
What a diagnosis covers
The order is standard and starts cheap. The oil’s level and condition are checked, along with when it was changed and with what. The fault codes are read. The engine is listened to with a stethoscope cold and warm — which shows whether the sound goes or stays. If the oil shows neglected servicing, the first step is often an out-of-schedule change with the correct viscosity and a week of listening: the ticking frequently disappears on its own.
If the sound remains after an oil change, the rocker cover comes off and the mechanism is assessed. The timing drive is usually checked at the same time, because nobody wants to dismantle the same area twice.
The same “oil first, metal second” logic works on other engines; a clear example is in EP6 balance shaft knock on Peugeot and Citroën.
How the repair is decided
Half the cost here is access to the parts rather than the parts themselves. That is why mechanics often suggest closing all the top-end work at once — lifters, the timing drive if it is due, and the rocker cover gasket that has to come off anyway.
Two questions worth asking. Whether the oil passages and the pick-up were assessed, because a fresh set of lifters fed through blocked galleries ticks again within months. And what the risks of leaving it are — driving with noisy lifters has its own breakdown in what happens if you drive with noisy hydraulic lifters.
One more detail: not every new sound in a car comes from the engine. Before going deep into the valvetrain, make sure you are not hearing the brakes — their language is covered in telling brake pad wear by ear.
If you want to know whether to go in tomorrow, record the sound with the Pro-Stuk app: once right after a cold start, once on a warm engine at idle. The app matches the recordings with your answers and shows the likely causes with percentages, and the difference between the two recordings tells a mechanic a great deal by itself.
