When you hear a loud thudding noise under your hood, you need to check the engine mounts immediately. The motor mounts are special components that keep the engine securely fixed to its position. But due to constant vibration caused by the car's motion, there's a fat chance for these mounts to come loose. You may experience several engine problems when this happens. That's why it is very important to do some troubleshooting, so you can fix the issue ASAP.
Thumping noise around the engine is the most prominent sign of slacking engine mounts. The noise comes from the engine block itself being thrown at the walls of the compartment. You have to stop this right away or else your engine will incur severe damage. To look for fractures on the mounts, you need to pop up the hood and do a physical inspection. It's better if you have a flashlight so you can really see even the smallest rupture on the mounts. But if you see that the mounts are still in good shape, it's possible that the problem is caused by the bolts. Make sure to tighten the bolts to keep the engine block steady.
Under your hood, there is a very limited space for everything. When the engine tilts even just a little, it may interfere with other components. In the case of latest trucks and cars where the radiator fan is connected to the engine, broken mounts can cause the engine to move towards the fan. When this happens, the engine and the radiator can be damaged by the fan blades. Again, you should peek inside the engine compartment and check if the fan is touching the engine or radiator. Replacing the mounts is necessary to keep the engine from moving.
Extreme engine movements can also affect the manifold or tail pipe connections, which often result in exhaust gas leaks. Seals and CV joints may also come off. This scenario is known as torque steer. To diagnose the culprit of the problem, you need to inspect not just the engine, but also the exhaust pipe connections at the manifold and tail pipes. If you see that the current mount is cracked, install a new Mazda Millenia engine mount to make sure that the engine stays fixed despite extreme mechanical vibrations.