Engine wear causes vibrations, leaks and idling problems due to worn engine mounts, clogged crankcase ventilation and porous return hoses. These components wear out after 6 years or 100,000 kilometres and, if neglected, can lead to serious engine damage. If you recognise the signs in time, you can avoid expensive repairs.
Worn engine mounts: vibrations and clunks when accelerating
Engine mounts are rubber components that attach the engine to the chassis. They damp vibrations and prevent the engine from hitting other components during acceleration or braking. Over time, oxygen, temperature and ozone cause the rubber to lose its elasticity.
After around 100,000 kilometres, engine mounts often need replacing. Manufacturers do not specify fixed replacement intervals, so it is sensible to check them at every inspection. On models such as the Ford Focus, complaints about vibrations and engine movement are regularly reported after 6 years.
You can recognise worn engine mounts by these symptoms:
- Increased noise levels in the cabin, especially when idling
- Strong vibrations that increase when cornering
- Severe movement of the gear lever
- Failure of flexible hoses in the braking system
- Accelerated wear of driveline components such as the prop shaft
Replace all engine mounts at the same time, even if only one is directly defective. This ensures even support and prevents new problems in the short term.
‘ Oil pressure drops and the engine sustains severe damage. ’
Crankcase ventilation: pressure and contamination disrupting the engine
The crankcase ventilation system routes exhaust gases from the engine block to the inlet manifold, where they are burned again. This prevents contamination and keeps the engine efficient. Without properly functioning crankcase ventilation – the system that removes excess gases from the crankcase – dangerous pressure builds up in the engine block.
Clogged ventilation occurs when oil, soot particles and white sludge accumulate in ventilation hoses or filters. Flow is restricted and crankcase pressure rises. This disrupts engine operation and can lead to more serious problems.
Consequences of increased crankcase pressure
A defective crankcase ventilation system causes measurable problems. Oil leaks via the crankshaft seal or gaskets are often the first sign. In addition, an irregular idle speed occurs, fuel consumption increases and the engine warning light may come on.
Cracked ventilation hoses lead to the intake of false air. This extra, unmeasured air disrupts the fuel-air ratios and causes irregular engine behaviour. Regularly check ventilation hoses for cracks or blockage.
Freezing in cold conditions
The temperature in the crankcase breather can remain below 70 degrees Celsius on some engines. In that case, water vapour can freeze in the hoses. This causes blockages that raise crankcase pressure. In extreme cold, water in the sump itself can freeze, with ice blocking the supply of oil to the oil strainer. Oil pressure drops and the engine sustains severe damage.
Contaminated throttle body: poor idling and hesitation
A contaminated throttle body often results from defective crankcase ventilation. Oil-bearing vapours form a layer on the throttle body, preventing it from opening and closing smoothly. The result is poor idling, hesitation under acceleration and increased fuel consumption.
Clean a contaminated throttle body with special cleaning sprays. Remove the throttle body from the inlet manifold and spray the inside thoroughly. Allow the cleaner to soak in for a few minutes and wipe the valve dry with a clean cloth. At the same time, check the ventilation hoses for contamination.
Engine block problems: leaking return hoses and coolant
Thin plastic return hoses to the coolant reservoir become porous after years and start to leak. These hoses return excess coolant to the reservoir. A leaking return hose causes coolant loss, which can lead to overheating and severe engine damage.
Replace a leaking return hose as soon as possible. The hose itself is easy to access and can be replaced with basic tools. When replacing, also check the hose clamps and ensure a proper seal. After fitting, top up the coolant reservoir to the correct level.
O-rings and thermostats: common leak points
O-rings in the cooling system can harden over time and lose their sealing ability. This causes small leaks that are difficult to trace. Regularly check for coolant loss and inspect the engine bay for drip marks.
Thermostats can also start to leak. A defective thermostat disrupts the engine’s temperature control. The engine either fails to reach operating temperature or overheats instead. Replace a leaking thermostat, including the associated gasket or O-ring.
‘ White sludge can accumulate in the sump and clog the entire crankcase ventilation system. ’
White sludge: a warning sign
White sludge consists of mixtures of oil debris and moisture. It forms when engines never reach operating temperature. This mainly occurs with frequent short trips, defective thermostats or insufficient maintenance.
White sludge can accumulate in the sump and clog the entire crankcase ventilation system. In winter it can freeze, making the problems worse. Prevent white sludge by regularly taking longer journeys and allowing the engine to reach operating temperature.
Underlaying engine problems: worn piston rings and cylinders
Increased crankcase pressure can indicate worn piston rings and cylinders. These components control the amount of oil that passes the piston into the combustion chamber. When worn, this leads to excessive oil consumption and vapour.
If you notice increased oil consumption or crankcase pressure problems, perform a compression test. This test measures the pressure in each cylinder and shows whether pistons, piston rings and cylinder edges are still intact. Depending on the test results, honing the engine block and replacing the piston rings may be sufficient, or full piston replacement may be required.
Maintenance tips: checking crankcase ventilation and engine mounts
Regular inspection prevents many problems. At every service, check the engine mounts for cracks and loss of elasticity. Test the crankcase ventilation by checking hoses for contamination and proper flow.
Plan preventive maintenance after 100,000 kilometres. Replace engine mounts even if no clear symptoms have appeared yet. Clean the crankcase ventilation system with special engine flush products and replace worn valve membranes that no longer open or close correctly.
Use the correct engine oil and change it according to schedule. Contaminated oil promotes sludge build-up. Make sure all connections in the crankcase ventilation system are watertight to prevent moisture ingress. In cold climates, check that any heating elements are working correctly.
‘ Thorough diagnostics prevent small problems from turning into expensive repairs. ’
When to visit a garage for engine wear
Go to a garage if you experience unexplained vibrations, oil leaks or irregular idling. These symptoms often point to several underlying problems that reinforce each other. Thorough diagnostics prevent small issues from developing into expensive repairs.
Monitor engine noises and watch out for warning signs such as an illuminated engine warning light. Abnormal sounds can give early warning of problems with engine mounts or crankcase pressure. Trust your instincts: if the car feels or sounds different, have an inspection carried out in good time.
On the Carnews website you will find much more information about engine problems, maintenance schedules and practical repair tips. Discover which problems occur with your car make and model and learn how to avoid costly repairs.
Frequently asked questions
Early signs of worn engine mounts include more vibration in the cabin (especially at idle), extra engine noise and noticeable movement of the engine or gear lever when you accelerate or change gear. Knocking or thumping noises can also occur when pulling away, braking or driving over speed bumps. If you ignore this, the engine can move too much, which leads to increased wear or failure of flexible lines (such as brake lines) and driveline components. In the long run this can seriously affect the car’s safety, driving comfort and reliability, and result in expensive repairs.
A properly working crankcase ventilation system removes blow-by gases and oil vapours in a controlled way to the intake so they are burned again, prevents pressure build-up in the crankcase and limits contamination/sludge in the engine and oil. In addition, the system helps prevent leaks via seals and gaskets and contributes to a stable idle speed and correct air–fuel ratio. With a defective system, excessive crankcase pressure occurs, which can lead to oil leaks, increased oil consumption, rough running and higher fuel consumption. Long-term defective crankcase ventilation accelerates engine wear (including seals, piston rings, cylinder walls) and can ultimately lead to serious engine damage and a shorter service life.
Neglected engine mounts can cause extra vibrations and misalignment, which in the long term leads to accelerated wear of drive shafts, exhaust parts, gaskets and even cracks in the engine block or sump. Poor or clogged crankcase ventilation can cause overpressure in the crankcase, with oil leaks via seals, contamination (sludge), rough running and ultimately severe engine damage due to oil starvation or freezing. You can prevent this by having engine mounts checked preventively around 100,000 km (or if there are vibrations/knocking) and, if necessary, replacing all of them at the same time. Regularly check and clean the crankcase ventilation system, replace worn hoses/valves and make sure oil changes are carried out on time so that sludge and pressure build-up do not get a chance.
As a rule, it is advisable to replace engine mounts preventively at around 100,000 km, especially if extra vibrations, noises or movement of the engine are already noticeable. You should replace or clean the crankcase ventilation system preventively when inspection reveals contamination, sludge, blockage or cracked hoses, or if there are symptoms such as increased crankcase pressure and oil leaks. Factors that determine the decision include mileage, driving conditions (many short trips, cold climates), visible wear/defects and noticeable symptoms (vibrations, oil consumption, irregular idling). The maintenance history and the desire to prevent serious engine damage also play a role when choosing preventive replacement.