Diagnostics — knocking in the engine compartment

If the engine is cold, then knocking in the engine compartment is not necessarily a cause for concern. On the contrary, when the engine is warm, knocking and noises during rotation almost always indicate serious damage. The most common damage to connecting rod bearings. The crankshaft main bearings—your Focus has five—are less likely to break. Bearing damage always entails an extensive engine overhaul. With a lot of luck and good hearing, you will recognize bearing damage at an early stage. If this is the case, then it is enough to just change the plain bearing shells of the corresponding connecting rod or main bearing - although usually a specialist will advise you to carry out a more extensive repair (crankshaft grinding, nitriding, installation of new bearings) or purchase an engine section.

This is how you recognize bearing damage

Accelerate the engine in place to medium speed and release the gas. If a slight knock appears as the rpm decreases («Knock-Knock») and you notice a similar noise also when accelerating smoothly, have the engine checked by a specialist workshop right away. Noises are typical for connecting rod bearing damage.

Ignored initial light tapping «Knock-Knock» after a few kilometers it will turn into a hard knock: the bearing damage has worsened, the liner has already worn out and most likely led to damage to the crankshaft. You can no longer think about inexpensive repairs. It is necessary to purchase an engine for an exchange or an engine section.

Uniform, increasing synchronously with the engine speed, rolling noise in the connecting rod and crank mechanism most often indicates damage to the main bearing. Stop the engine immediately and have the damage diagnosed by a workshop. If you wait too long, the engine block will become unusable as an exchange unit. This will unnecessarily skyrocket the cost of the repair as your dealer will quote the bad unit as a new part.