When should the timing chain be replaced?
The engine’s sound can reveal many things. The noise of a stretched timing chain can be heard when starting cold: the engine is very noisy in the first few seconds, and then it calms down. After the first start, the car runs well without noise, but this is an indication, as mentioned, of a stretched chain. Under these circumstances, continuing to use the vehicle may cause the timing chain to break with partial or complete engine damage. Therefore, paying close attention to abnormal noises will help avoid expensive repairs.
Mercedes timing chain replacement
Clear the engine’s upper part to gain access to the chain
On this engine, the timing chain is located at the rear, between the engine and the gearbox. If we need to replace only the timing chain, we can do this with the engine in situ. However, if any of the guides is defective, broken or excessively worn, we must disassemble(take out, remove, extract) the entire engine.
We’ve disassembled the airbox, the brackets, the engine wiring loom, the injectors and, finally, the cover.
As suspected, the chain is loose, so it has stretched.
Do you hear strange noises when you start the car? Don’t ignore them!
We removed the chain tensioner and loosened the cam sprockets bolts. The black deposits on the camshaft carrier caps indicated that the oil was not in good condition; regular servicing is essential for all engine components, including the timing chain.
Inspect the chain guides
With the camshafts and sprockets taken out, we’ve gained access to inspect the guides. You can replace the timing chain on the spot if they are in good condition. Otherwise, you must remove the engine and replace the guides.
Fortunately, in this situation, the guides were in good condition.
We replaced the sprockets because they wear out over time (the teeth were rounded).
Timing chain replacement procedure
The procedure for replacing the timing chain is as follows: a rivet is removed from the old and new chains using a special tool and joins the two chains at one end. The old chain is carefully pulled out to put the new one in its place. Then, the new chain is riveted securely using the same tool.
Reinstall all the components back and service the car
We installed a new timing chain, sprockets, and a hydraulic tensioner, completing all the work without taking out the engine.
Now the timing chain is perfect!
We cleaned the injector’s holes and changed the seals, putting each injector in its place.
Lack of maintenance is never a good idea
We have seen that this car has not been serviced regularly (remember how the oil was?). The air filter was also filthy!
You can see the entire procedure on our Youtube channel: Timing Chain Noise – diagnose & replacement