What causes a loud knocking sound in the engine? 2000 ford focus

If a vehicle is smoking then it is obviously burning oil, loud noises from bottom of engine usually indicate main bearing failure, but that wouldn't usually make smoke are you sure it is from bottom of engine. Sounds more likely to me that you have either valve or piston problems, a valve seal gone would result in smoke as oil leaking into Cylinder chamber would burn producing smoke. Piston ring failure would also produce smoke and most likely a significant loss of power with possible noises resulting from broken pieces of ring in the cylinder impacting on head, this may have also unseated a valve causing the smoke. To check ring or valve failure you need to do a compression test, to check for bearing failure I am afraid it will require inspection either by removing sump pan ( oil pan) and removing bearing covers to check for damage.Whatever the cause it sounds as if it may be quite expensive and age and condition of vehicle should be taken into account, after all with the cheap cars on ebay it may be more cost effective to cut your losses and replace the vehicle.

Here's a video Dennis Weid. suggested as a solution to your problem from YouTube:


Ford Focus 1.8 TDCi 115 engine problem - knocking/ticking sound

check for broken exhaust pipe or muffler could have hole rusted through muffler or check around exhaust manifold for exhaust leaks.

check bolts on wheel at crank

exhaust flex pipe?

remove the intake manifold ,remove radiator ,remove radiator intake and outake housing, remove fan ,remove all belts: power steering, alternator and if you have a/c, remove harmonic balancer ,remove timing belt covers, remove timing belt remove intake housinng once you have remove all the above, your freaken engine will look naked, you can see the location of the knock sensor is locate in the engine valley

Go to Orielly auto parts and rent their OBD scanner. If you takethe vehicle to them they wont charge you for the scanner. The dealer will charge you $100 or more to check it for you. Depending on how loud the knock is I would not recomend driving the vehicle until you scan it. Once you scan it write down the codes and Oriellys can translate them for you also.

Sounds to me like a very common problem has occured to your neighbor. If this is a SOHC engine, one of the valve seats in the number 4 cylinder has fallen out. I'm sure it has damaged the head and the piston. Stop trying to run it or you might blow a hole in the cylinder wall or break a rod or both.

this can be a serious problem, sounds like one of your engine valves, has the car overheated recently? if your valves bent, you need to take the engine apart hope i helped

Possible oil sending unit problem.