I always wondered how does an oil filter – the boring part of its cool cousin 😉 worked. Turns out it is rather simple and boring – just filtering the oil!
So, how does a motorcycle oil filter work? The oil filter receives the engine oil through the oil holes on the top cover. The oil is then guided to the paper pleats which absorb the contaminants in the oil and filter them clean.
The clean oil then enters the center tube of the filter wherein the filtered oil is guided out of the filter to make room for the unfiltered oil to enter in.
There is a bypass valve as well to ensure oil flow in case the filter gets clogged.
Now, let’s discuss in detail:
- How exactly does an oil filter work
- Main parts of an oil filter
- How does oil flow through the oil filter
How Does An Oil Filter Work?
First, the oil filter receives the unfiltered oil through the oil holes present on the top cover. Don’t stress, we will discuss what the top cover is and all the other parts in detail. Just hang in there for now.
Second, the oil is then guided to flow through the paper pleats. Paper pleats are the filtering part which you have seen as these yellow or pink paper arranged beautifully in the filter.
This is where filtering happens. The paper pleats are made of a special material designed to absorb the oil contaminants – be it dirt, dust, metal particles and many other types of contaminants.
Third, the filtered oil from the paper pleats then flows into the center tube. The Center tube provides the passage for the now clean oil to move out of the oil filter.
As the cleaned oil moves out of the oil filter, it makes way for the new unfiltered oil to enter into the filter. And the cycle keeps on.
Lastly, there is a bypass valve provided as a fallback mechanism in case the paper pleats (the filtering component) get clogged. In such a case, the bypass valve guides the unfiltered oil directly into the center tube so that it can move out of the filter.
This bypass mechanism ensures that the oil keeps on flowing, although not filtered so that the oil keeps on flowing.
Here is a cool animation video showing the oil filter working mechanism.
Main Parts Of An Oil Filter
Now, let’s discuss each part of an oil filter and what its functions are.
External Casing
The cylindrical metal casing also called the housing, is used to protect the oil filter from any mechanical damage.
The casing is usually powder coated and the outer surface is resistant to corrosion. The casing acts as the outer layer for the oil filter and is usually comes in black color. When you see the oil filter, you are mostly looking at the casing of the oil filter.
Top Cover
The top cover is essentially the top portion of the oil filter which the casing does not cover. You can see the top cover when you take out the oil filter.
The top cover consists of two important subcomponents. First, it has a precisely made high strength thread, which is used to fit the oil filter in the motorcycle. You will be using this thread to screw and tighten the oil filter to install into your motorcycle.
Second, there are oil holes on the surface of the top cover. Through these oil holes, the engine oil enters the oil filter and gets filtered from dirt, dust, metal particles, and other contaminants.
O-Ring (Gasket)
The O-Ring or the gasket is basically rubber or an elastic material used to seal the oil filter and ensure that the filter is fitted tight.
The elastic material used should be resistant to thermal expansion and withstand mechanical loads.
Anti-Drainback Valve
As the oil flows into the oil filter through the oil holes on the top cover, the anti-drainback valve – placed right beneath the top cover – ensures that the oil does not flow back through the oil holes.
The anti-drainback valve also ensures there is sufficient oil and no priming issues in the filter during the engine startup.
The material used for this valve is usually a flexible material with a specially designed structure to suit the oil filter needs.
Paper Pleats
Paper pleats are the component that actually filters the contaminants from the engine oil.
As the oil enters through the oil holes and passes the anti-drainback valve, they flow through these paper pleats wherein the dirt, dust, metal particles, and many other contaminants are absorbed by these plates. Thus, allowing a cleaner oil to flow through forward.
Paper pleats are made of high quality materials designed to absorb various types of contaminants from the engine oil and are resistant to any aggressive chemicals present in the oil.
Center Tube
The Center tube is around where the paper pleats are arranged in a symmetrical fashion. The tube is spiral in shape with pores along its surface to allow the oil flow.
As the oil flows through the paper pleats and gets filtered, the filtered oil flows into the center tube through the pores on its surface. Once the filtered oil enters the tube, it then flows along the tube and exits out the filter as clean oil.
In short, the center tube has two functions – one, it acts as the support for paper pleats; and two, it provides a passage for the filtered oil to flow out of the oil filter.
Bypass Valve
The bypass valve is placed right below the center tube. The bypass valve ensures that the oil flows to the crankcase even when the oil filter is clogged.
Bypass valve, also rightly called pressure relief valve, allows free flow of the oil whenever the oil flow gets restricted otherwise in the filter. The oil flow restriction can arise whenever the filter is clogged or the oil is too thick.
How Does Oil Flow Through A Filter?
The oil is pumped into the oil filter, which enters the filter through the oil holes present in the top cover.
Once the oil enters the filter through the oil holes, the anti-drainback valve located right below the top cover ensures it doesn’t go back out of the filter. From then on, oil flows into the paper pleats wherein the filtering of the contaminants happens.
The filtered oil, next up, flows through the paper pleats and enters the center tube through the pores of the tube.
The center tube provides a passage for the clean oil to move out of the oil filter. The clean oil easily flows through the tube and gets out of the filter paving way for the unfiltered oil to enter.
In short, oil enters the filter through the top cover oil holes, gets filtered in paper pleats, and exits through the center tube.
