Fan clutch is one of the most neglected part in most diesel vehicles today. Yes, car owners don’t know how this clutch system works and how should it be serviced. They just buy the vehicle and drive, that’s it.
But if you are an automotive junkie like me, you must also know how to maintain this particular component in your engine. After all, it helps keep your engine temperature cool so it’s quite important that you keep a maintenance schedule for this particular fan.
In this post, I’ll educate you what is fan clutch, how it works and, how you can do its main maintenance task – silicone oil top up / refill. Read on to learn more!
What is a Fan Clutch?
Fan clutch is a “clutch system” that mechanically engages and disengages the main engine’s cooling fan, hence it’s called fan clutch. It is driven by a pulley that is directly attached to the engine.
It has two portions – the drive portion and the clutch portion. These portions have sheer plates, independent plates that are aligned with circular fins that interweaves each other very closely but never actually touch, so there’s no friction between the two plates. Another part of a fan clutch is its silicone oil reservoir.
Fan clutch is viscous because it is lubricated by a silicone gel (commonly called as silicon oil) inside the clutch that uses friction to help engage the fan.
There are several mechanisms that are used for fan clutches:
- Air-engage fan clutch
- Spring fan clutch
- Air-sensing viscous fan clutch (self-contained type of fan clutch)
Regardless of fan clutch type your vehicle has, they all provide similar function which is to provide air to help cool down your radiator. Hot engine coolant passes through the radiator and is being cooled down by the fan clutch as the fan is directly facing the radiator. This makes the cooler water to enter the engine block which helps maintain the optimum temperature of your engine.
Read here to learn more on how to flush the cooling system.
How does a Fan Clutch Work?
When you initially drive your car, the temperature still needs to get warm before the clutch engages. Inside the fan clutch, the reservoir valve that expands once your engine reaches certain temperature (75°C to 90°C).
This pin acts like a valve which allows the viscous oil to flow or “engage”, which allows the fan to cool down the engine when its get hot. In this state, the fan blade rotates or spins at the same speed as the pulley.
When you are driving at a high speed, your car naturally cools down by natural air that enters the engine. This helps cool the valve inside the fan clutch which allows the silicone oil to reenter its reservoir disengaging the clutch.
The process continues as you drive your car.
Now overtime, your fan clutch will have a hard time engaging that clutch, which will lead to your engine to overheat as the fan is not cooling your radiator.
This is a common symptom that your fan clutch’s silicone oil should be replaced or refilled with new fluid. So how do you top up your fan clutch?
How to Refill Your Fan Clutch with Silicone Oil?
First off, your fan clutch is attached to fan blade that is made of plastic. As mentioned earlier, fan clutches are found directly mounted to the engine through a pulley. So it is situated at the front portion of the engine bay.
In diesel engines with rear-wheel and 4×4 drive system, fan clutches acts like a radiator fan.
Second thing to do is to disassemble the fan clutch from its pulley. This can be challenging especially if you are a DIY beginner, but of course doable. In some engine designs, you may need to take out some drive belts in order to pull out the fan clutch.
Once you removed the fan clutch, you need to remove the bolts that holds the fan blade using a 10mm wrench. After that, you may need an impact drive or an impact wrench to remove the fan clutch bolts. These bolts are very tight so you need those tools if you want to open the clutch fan.
Check out Amazon for the best impact drive and impact wrench brands.
Once you unbolt all the screws, then you can now open the fan clutch. Some fan clutch may still give you a hard time opening it, so you may need a flat head screw driver and pry at the middle to open the fan clutch.
The internal parts of the fan clutch include the drive and clutch portion, including the reservoir. Inspect the existing stock silicone oil and if it’s worn out, then drain all the fluid before refilling.
You can now refill your clutch fan with new fresh silicone oil. But the question is, how much silicone oil is needed?
Fan clutch differs from each other depending on the size of the engine. So you have to check your owner’s manual and see the right quantity of silicone oil required for your fan clutch.
Common requirement is 10,000 CST silicone oil and about 18ml for small fan clutch types.
Once you filled some new silicone oil to your fan clutch reservoir, then just do the procedure in reverse and reinstall everything. And you are done!
Summary
I hope you learned how to refill your fan clutch with silicone oil. This is an essential maintenance procedure that should be done regularly on fan clutch-based engines.
Here is my experience replacing silicone oil in my Mitsubishi Monterosport. This video is in Tagalog language but has English subtitle, enjoy!
