Astron II Common Problems

From Mitsipedia

Many of the people reading this site have probably heard the horror stories about the Mitsubishi Astron II engine. Are these justified? no. The Astron II is quite a reliable engine if maintained properly. The most common problems that seems to face them are:

Oil leaks

If you see a clean Astron II it is like winning the lottery. More often than not Astrons leak oil. The most common places are:

  • At the back of the engine under the air conditioning pump where the timing case, sump and block mat to each other
  • From around the oil filler cap. I have no idea what causes this, but it is often easily fixed by doing the oil filler cap up fully then turning back around 1/4 of a turn
  • From the water pump side cam seal
  • From the rocker cover - this is usually caused by not using RTV sealant where the "half moons" sit on the head and where the rocker gasket meets these.


A loud metallic rattle that occurs when the engine first starts up and sometimes at idle on 1985-1990 model engines normally indicate that the balance shaft chain requires adjustment.

If the same noise is heard on later model Astron IIs, the timing chain, balance shaft chain and guides probably need replacement as they use a self-adjusting chain on the balance shaft.


If you start the engine and it blows a little blue smoke and then clears itself, it generally means that the valve stem seals need replacing. This is quite common on these engines and isn't too bad to repair.

If the engine smokes all the time there is usually one of two causes:

  • The oil needs changing - this is easily checked by pulling the dipstick out. If the oil runs off the stick like water - you are due for an oil change.
  • The engine needs reconditioning.

Water pump

The water pump on the Astron II seems to last a good while but when it starts dripping coolant from the little hole in the bottom of it, it is time to start looking at replacing it.