Oil seepage from engine and gearbox is often the first sign that a seal or gasket is ageing. A thin film of oil is not necessarily an immediate danger. Ignoring it can, however, lead to serious leaks and expensive repairs. Read on. Find out how to spot it. Find out what you can do.
What exactly is oil seepage?
Oil seepage is not a classic leak. It is a light sweating or oil film around gaskets, seals and joints. Seals lose their elasticity. This happens due to age, heat or the wrong oil. On the engine you often see it around the rocker cover and the sump. You also see it around the crankshaft seals and the oil filter housing. On the gearbox, seepage usually appears at seals, sump gaskets and sometimes at drain or filler plugs.
A light film is mainly a warning sign. It means you need to keep a close eye on the seal before it develops into visible drops or oil consumption. Oil that drips regularly or increases quickly calls for immediate inspection.
‘ The problem is not unique to this model. ’
Oil seepage on the Dacia Sandero
Owners of the Dacia Sandero sometimes report oil sweat around the driveshaft seals, especially on the driver’s side. This is a common issue with older examples or models with high mileage. The driveshaft seal keeps oil inside the gearbox and dirt out. If the seal hardens or cracks, oil can seep out.
On the Sandero, seepage can also occur at engine gaskets, especially if the car has been run for years with the wrong oil or if servicing has been irregular. The problem is not unique to this model. It does occur regularly under heavy use. Longer service intervals increase the risk.
What causes oil seepage?
Oil seepage from engine and gearbox has several causes:
- Ageing seals: Rubber and gaskets lose their elasticity over time and due to heat. This occurs mainly on cars more than five years old or with over 100,000 kilometres on the clock.
- Wrong oil: Every manufacturer specifies a particular oil type with a certain viscosity. Deviating from this can damage seals and make lubrication more difficult.
- Oil level too high: Overfilling causes pressure build-up in the sump. That pressure forces oil past seals more easily.
- Heat load: Prolonged high temperatures damage hoses and seals. They can also crack.
- Mechanical wear: Worn seals cause real leaks. Damaged sump components do the same. Cracks in metal parts lead not only to seepage but to complete leakage.
How do you recognise oil seepage?
You can recognise oil seepage by a few clear signs. Look for dark oil on the underside of the engine. Also look for brown oil on the underside of the gearbox. This usually points to sweating or an early-stage leak. Oil around sump joints is a very common sign. Oil around the edges of a cover or a seal as well.
Regularly check the parking spot under your car. A slightly damp stain is less worrying. Small drops are a stronger warning sign. For transmission fluid, colour is important. Light, translucent fluid is normal. Dark, thick fluid points to wear and problems. Burnt-smelling fluid does too.
Differences between engine oil and transmission oil
Engine oil is usually dark brown. It has a distinctive smell. Transmission oil is often lighter in colour. It is sometimes reddish. It smells sharper than engine oil. Check the colour and smell. That way you can more quickly determine where the oil is coming from. It helps you locate the problem.
‘ The wrong oil accelerates the problem. ’
What can you do yourself about oil seepage?
You suspect oil seepage. In that case carry out a few steps yourself to assess how serious it is. Check the engine oil level. Check the gearbox oil level. Consult the service book for guidance. A low level can indicate a leak. A high level can actually cause seepage.
First clean the underside of the engine thoroughly with a degreaser. Also clean the underside of the gearbox. Then drive normally for a few days. Look again to see where the oil reappears. This makes it easier to find the source. You also see whether it is just an old oil deposit. Or you see that it is an active leak.
Always use the oil specified by the manufacturer. The correct viscosity ensures that seals work properly. The correct specification ensures proper lubrication of components. The wrong oil accelerates the problem. It will not solve it.
When should you go to the garage?
You can monitor a light oil film for a while. Droplet formation is a sign to go to the garage immediately. A rapid increase in oil loss is another. If seepage keeps coming back, do not just top up the oil. Have the gasket or seal checked as well. Timely replacement prevents more serious damage.
On the gearbox, oil loss carries major risks. It can quickly lead to damage to gears and bearings. Transmission oil provides lubrication and cooling. It also protects gears and bearings. Too little oil leads to overheating. It also causes wear and costly repairs. On automatic transmissions, leaks cause problems within a short time. The fluid is needed to build up pressure. It is also needed for shifting.
Repair options for leaking seals
A leaking driveshaft oil seal usually needs to be replaced. The repair consists of three steps. First the mechanic removes the driveshaft. Then he removes the old seal. Finally he fits a new one. This is a labour-intensive job. At a garage it takes between two and four hours. The duration depends on the model. Accessibility also plays a role.
Some owners report that stop-leak products provide temporary relief. These products make rubber more supple. This only works in cases of drying out. It does not work for mechanical damage. Stop-leak does not replace a proper repair. It does help to buy time until a planned garage appointment.
Can oil seepage be prevented?
Regular maintenance reduces the chances of oil seepage. Replace oil and filters according to the manufacturer’s recommendations. Always use the correct specification. Keep an eye on the oil level and top up when needed, but avoid overfilling.
At every service, check the underside of the car for oil traces. Also check after every parking period. Early intervention prevents light seepage from developing into a major leak. Avoid long periods of extreme load. Think of full loading at high temperatures. This increases the pressure on seals.
‘ The consequences are serious and often lead to major damage. ’
Why you should not ignore oil loss
Oil loss can sometimes seem like a minor issue. The consequences are, however, serious and often lead to major damage. Too little engine oil leads to increased friction. It also leads to overheating and ultimately engine damage. On the gearbox, oil loss results in accelerated wear. Gears and bearings wear out faster. Synchro rings too.
An engine or gearbox can completely seize due to lack of lubrication. This happens mainly in more serious cases. Replacing a seal or gasket at an early stage costs little. The repair costs for seized components are many times higher. Leaking oil ends up on hot exhaust parts. This can be a fire hazard.
Practical tips for car enthusiasts
Keep a logbook of your oil consumption. Also note any observations under the car. This helps you recognise patterns. You will notice any deterioration in good time. If in doubt, place a piece of cardboard under the car. This makes drops easier to see.
Check the underside carefully after long journeys. Heat-related issues often make leaks more visible. Heated oil becomes thinner. It seeps out more easily. Check whether there are oil traces visible on the wheels. Also look around the driveshaft, especially after washing the car.
On the Carnews website you will find much more information about engine problems. You will also find maintenance tips. In addition, there is practical advice for Dacia owners. Owners of other brands will also find useful information here. Discover more articles and expand your knowledge of cars and technology.
Frequently asked questions
Oil seepage is a light “sweating”: a thin film of oil around gaskets, seals or joints, without obvious drops on the ground or the oil level falling quickly. You recognise it by slightly greasy, somewhat dusty patches on or around the engine/gearbox that do not actually drip. A more serious oil leak gives visible wet oil, drops or puddles under the car and often a noticeably falling oil level. If the area becomes wet again shortly after cleaning or droplets start to form, then it is no longer normal seepage and it must be investigated immediately.
Common causes of oil seepage include aged or hardened gaskets and seals, which means they no longer seal properly. An oil level that is too high can also create extra pressure, causing oil to sweat out past seals. In addition, using the wrong oil specification can damage the seals. Finally, heat load and mechanical wear or slight damage to sump parts and connections also play a role.
Oil seepage is usually not an immediately dangerous leak, but it is a sign that seals are ageing and that you need to keep an eye on it. Regularly check the oil level, make sure the correct oil (as specified by the manufacturer) is used and that the level is not too high. Clean the area once and then check after some time where the oil comes back, so you can pinpoint the source more accurately. If you see actual droplet formation or the oil traces increase quickly, have a mechanic check the gaskets or seals as soon as possible and replace them if necessary.
You should go to the garage if the oil film returns quickly after cleaning, if there are drops under the car or if the oil level is measurably falling. A light, stable oil film can be monitored and assessed at the next service. If only a small gasket or seal needs replacing, costs are roughly between about €150 and €400, depending on labour time and the type of engine/gearbox. If several seals or parts of the engine/gearbox have to be dismantled, the costs can rise by several hundred euros more.