Wrong turn: where is the oil on the air filter and what to do with it
Probably, someone noticed such a phenomenon: when replacing the air filter, traces of oil are noticeable on it. Most often in the form of a spot, individual drops are sometimes noticeable. How to get there? This is dangerous? Sometimes yes, it’s dangerous. And sometimes not.
Everything’s under control!
Let’s start with the good: sometimes filters are heavily oiled, straight from the factory. This is not about the usual acrylic or phenolic impregnation of paper, which gives it a white or yellow color, respectively, but about oil impregnation. Such filters (although more often repair, rather than disposable), soaked in oil, are usually found on motor vehicles: motorcycles or ATVs. They need a lot of air and cleaning, and they tend to travel to places where there is too much dust. But sometimes these filters are also installed on cars, for example, on some Subaru or Nissan. And if it suddenly seems to you that the filter of your car is in oil, it makes sense to clarify first: perhaps it should be so.
Photo: Kevin Seibel of Unsplash.com
Well, if the car has a filter with a simple paper curtain, and an oil stain spreads on it, you need to find out where it came from. This should not be in any case, but you need to understand what is the reason for such a disaster. Sometimes this is a sign of a very serious problem, and sometimes it is solved quite simply.
Other people’s problems
Let’s first analyze the situation when the filter is in the oil on a completely unfamiliar car. For example, by inspection before buying in the secondary market. Here is an important factor: you do not know exactly how this car was repaired. Of course, the seller can say that he changes the oil every seven thousand kilometers, fills in only the “best" oil and puts in original filters. But we know … So, in the case of an unknown car, we can consider not the saddest, but very undesirable option – clogged engine oil channels due to lack of normal maintenance. First of all, the oil separator is clogged.
Here the mechanism is simple: the oil enters the air filter only in the case of an exorbitant increase in pressure in the crankcase. One of the reasons for this growth are channels clogged with sediment. The oil pump pumps and the channels are clogged. The oil has nowhere to go, it is left alone with all its mass of crankcase oil mist to go through the crankcase ventilation valve into the intake air. And of course the air filter.
On the one hand, this is not the worst option. If the engine has not yet died, sometimes it is enough to change the oil a couple of times (in extreme cases, use flushing if there is nothing to lose) and the oil filter, and everything will return to normal. But you need to understand that if the machine was not monitored and brought to such a state, then nothing working may remain. And, of course, do not rush to buy such an instance.
A simple check in this case is to remove the filler cap. If the gases escape quickly and even the oil mist escapes, the pressure is clearly not normal. True, as I said, the reason for the increase in pressure can be not only in clogged channels, so you should not think that this problem can always be solved by changing the oil and filters. Much more often, a worn-out cylinder-piston group is to blame for such an increase in crankcase gas pressure.
Sad and very expensive
A situation that they prefer not to think about is an increase in the pressure of crankcase gases and their penetration through the VKG valve. The pressure increase mechanism is simple: gases from the combustion chamber pass through worn piston rings into the under-piston space, and from there into the crankcase. And when they have nowhere to go, they try to break out anywhere: through the seals and pulling out the oil dipstick and, of course, through the forced crankcase ventilation valve.
Of course, if the car is yours, it will not be difficult to detect wear on the piston group. At least in terms of the growth of "maslozhora". Well, if the car belongs to someone else, then you should try to evaluate the totality of signs. Usually such an engine begins to "sweat" oil at all joints and looks dirty. Well, the classic is blue smoke from the chimney. Compression measurement will not hurt here – an increase in pressure in the crankcase is accompanied by its loss, so the differential will completely help rearrange all i.
If all or most of these symptoms are present, then it is too late to pour supprotek, dimexide or tincture of blue electrical tape – you need to repair the motor.
Unfortunately, in cars with high mileage and good maintenance, the reason for the appearance of oil in the air filter is precisely this: wear on at least the piston rings. Of course, you can try to wash the engine, but this is unlikely to significantly change the situation. It is better to prepare money and not delay the repair.
A trifle, but nice
Now a few words about the simplest and cheapest reason to lubricate an air filter: the positive crankcase ventilation valve (also known as PCV, positive crankcase ventilation). If this valve (CVKG) jams, then it will not be able to relieve excess pressure at high speeds and the gases will go where they should not. First of all, the throttle and EGR valve (if there is a recirculation system) will be filled with deposits, but if the situation is too neglected, oil mist gases will also be deposited in the air filter.
KVGK can be checked. The easiest way is to remove it and shake it (if it’s not stuck, it should strum). But if it is dirty, then it is better to replace it just in case (or replace its membrane, which is often possible and always cheaper). And of course, it will be necessary to flush not only the pipes of the VKG system, but also the oil separator and possibly the throttle valve (of course it is after the air filter, but if it is completely in oil, then the valve will be dirty).
In this variant of the KVKG malfunction, it is very successful to notice the oil in the air filter in time. If you continue to drive with a broken valve, much more serious problems can arise. At least due to the fact that the oil will press from everywhere and the engine will not have enough fresh air. And there will be no leakage of excess moisture, which will lead to the appearance of condensate in the oil, which can be found in the form of a whitish coating on the oil filler cap.
Finally, the turbine
Be sure to talk about the features of turbocharged engines. First of all, these points will concern diesel engines (which are now all turbocharged), but for gasoline engines the essence of the process will be the same.
Thus, in a turbocharged engine, it is the turbine that will drive the oil into the intake. Oil enters the inlet through the compressor part for two reasons: due to cartridge wear, or again due to a clogged crankcase ventilation system (in the second case, the procedure is the same – we begin to check the CVKG).
If the oil separator is heavily clogged, the pattern of oil entering the air filter will be the same as in a naturally aspirated engine, with the exception of one point: oil will not only settle on the walls of the pipes, but also begin to accumulate on them in the intercooler. And here everything can be more serious than a simple dirty air filter: if you crank the engine well, oil can splash out into the intake from there, and the engine will deteriorate (we are talking, of course, about a diesel engine). So on a diesel, an oily air filter should at least make you think.
By the way, the oil filter on a supercharged engine is not only a consequence of some kind of malfunction, but also another reason. The fact is that the turbine, due to a lack of air in the intake, will suck oil into the intake tract, and you yourself understand what this threatens. In general, everything is very interconnected here, and the oil in the diesel air filter is very serious. If it is, you most likely need to clean both the EGR and the entire intake.
To be afraid or not?
Of course, I would like to say that the oil in the air filter is not so scary. But, unfortunately, I will tell the truth: you don’t need to believe in miracles. I always want to hope that, they say, I will change the oil and the oil filter, and everything will pass by itself. Well, I’ll also change the PCV valve, and now everything will definitely be fine. It’s a shame, of course, but there is little hope for this. Most often, oiling of the air filter still occurs due to wear of the CPG, for the most expensive and intractable reason.
And, of course, you should not turn a blind eye to the problem. Especially when it comes to diesel. Well, in the case of a simple atmospheric gasoline engine, the oil in the filter can give a hint: either it’s time to think about repairs, or to sell the old car. Although now the second option no longer seems like a smart move.