Oil sealing system
Note that this is just a brief overview of the sealing system, in which important details are omitted for the sake of clarity.
Due to extreme working conditions (over 250 000 rpm and up to 1200°C), standard seals (e.g. O-rings) are not an option in case of turbochargers. Instead, a different approach has been taken by the designers. On both sides (compressor and turbine) of the element, there are oil outlets with special sealing ring.
When the element is working, the forces originating in the device push the oil to the outlet (from where it gravitationally flows down, back to the oil sump), while the sealing ring additionally secures and prevents leaks from originating.
So, in simplistic terms, the whole system is based on natural forces: centrifugal force and gravity.
Oil leaks – inspection
Identifying the source of any engine leak is not an easy task. The degree of complexity of modern turbochargers and engines is extreme and leaks (especially oil leaks) tend to make it way to a large portion of the engine. If not caught early on, spotting the place in which it originates might be very tricky.
If you plan to do it yourself, it is recommended to thoroughly clean the engine, with special attention paid to the spots where the leaks occur. Make sure to check it really carefully and clean everything away, as mistake at this point might be costly – in terms of time and money.
After the cleaning, start the engine and observe potential culprits – places from where the oil might be leaking. If no leaks are observed after a prolonged time, it might be a good idea to drive a few miles and then checking the leak again.
Oil leaks at turbine or compressor
Potential leaks might be observed at one or both sides of the turbocharger: compressor or turbine. Most of them do not indicate problems with the part itself, but rather with some other elements, which influence the operation of the turbo.
For instance, oil leaks can be caused by:
- problems with lines or ventilation (clogged, damaged etc.),
- worn out cylinders, piston rings and other engine elements.
Different oil pressure, obstructed or increased air flow disturb standard turbocharger’s operation, thus oil sealing system is no longer effective. In some cases, simply correcting the oil level is enough to solve the issue (if it is too high, the oil might not have enough room to drain from the oil outlet).
However, it is important to note that the causes of such situation are outside of the turbo itself. Removing the outside cause (e.g. replacing the damaged oil lines) will stop the oil leakage without replacing or reconditioning the turbo.
Naturally, there might be also problems within the housing – residue, sludge inside the housing, damage of bearing. It should be kept in mind though, that these issues are much less common.
Side note: if you drive your car mostly in city traffic, remember to regularly take the car for a more dynamic trip, at higher revs. It helps to burn all the residue and coke inside of the turbo’s housing.
Oil leaks at compressor only
Some of the leaks occurring on the compressor’s side are caused by different factors. In such situation make sure to additionally check (or start by checking) air filter system for any dirt, foreign matter which might distort the air intake.
Exhaust system should be inspected as well for any resistance in the gas flow, as it also could result in oil leakage at the compressor. It is a frequent situation after any modifications has been made to the exhaust. One example can be removal of DPF (Diesel Particulate Filter) or catalytic converter.
Moreover, dirt in the compressor itself or the air cooler might cause the issue as well.
Don’t (always) blame the turbocharger
As explained previously, the design of the oil sealing system in a turbocharger is such, that leaks might occur if other vehicle’s system are damaged or operate incorrectly. So before you decide on reconditioned turbo or a repair of the element make sure to check other, less expensive options first. If not discovered, they will still cause the leaks, even after you replace or rebuild the part.Make sure to conduct a thorough check – preferably by a professional at your local garage, who has the tools, knowledge and experience to properly identify the cause of an oil leak.