Fan Clutch Oil Change (1 Viewer)

[1JZGTE]

Hello folks,

Apologies in advance but I didn't know where this thread should go, so having looked at past topics on fan clutches, a lot of them were from this sub forum.

A bit of background - I live in Europe, where temperatures are typically up to 95F in the summer (it never really goes above this), down to about 25F in the winter months.

It has been quite hot here recently (around 95F or so) and the temperature gauge shows the car is overheating if traffic is slow moving or if it is idling for 10 minutes or more. So I am thinking its time to replace the oil inside my viscous fan clutch.

My clutch is an AISIN 2BK

I plan on taking it apart tomorrow, draining the old oil and filling it with up to 60ml of 7000cst oil.

Questions:

1. My fan clutch is an AISIN 2BK. I cannot find much on it. Is that particular model good or bad?

2. Given the temperature range where I live (25F to 95F), is 7000cst oil adequate?

3. Once I pop the clutch open, should I adjust any of the settings by turning the screws or should I leave it? My understanding is that adjusting the valves inside changes when the fan comes on while changing the fluid adjusts how powerful the clutch is once it is on

4. The thermostat spring is rusty do I clean that with a wire brush or should I use some rust eater paste on it?

Thanks in advance!

 

[Kernal]

What model/engine 80 series do you have?

 

[1JZGTE]

Hello, I don't actually have an FZJ-80, I have a Toyota Soarer (known as the Lexus SC300 in the USA) but when looking on the internet, this was the only place I found where there was such a huge amount of information and detail on this. Most other forums don't really know much about this at all. This is why I am asking here.

Incidentally, I split my clutch in half and this is how things look:

It looks to me that mine is an adjustable version. Any adjustment tips would be appreciated - I want it to kick in a little earlier, I understand that I need to adjust the screws in order to do this (but which way I do not know).

 

[jpoole]

You can read up on this forum to find a few posts showing the adjustment process, more details etc.

After researching up I'd likely do the following:

-rig up a way to put the clutch in hot water so that you can apply an even and controllable temp to it
-similarly rig up a reliable way to monitor the temp of the water
-slowly heat the clutch up and closely monitor at what temp it starts to open, when the stage is hit that goes from the smaller to the larger section of the orifice(s) and when it's fully open
-once you've documented the relevant temps you can loosen the two screws and rotate the mechanism to cause the opening to start/etc. at a lower temp or a higher temp. Note how it behaves after you make your changes.

Some of the temps referenced on mud are for halfway open, I think, but keep in mind that you may not want to just follow opening temps on mud but instead just adjust based on where you already are using your before/after temps as a guide/metric.

From there you can see how your changes relate to actual performance on the truck and further tune as needed. Keep in mind that oil weight and oil quantity will also impact how much air the fan clutch pulls and how it handles prolonged stress, etc. Also keep in mind that the coolant thermostat only opens at a certain temp so you want to roughly correlate air flow through the radiator with coolant flow through it, etc. In some ways the port opening on the fan clutch is very important as it allows it to start to function. In other ways the weight of oil is really important because once the ports are open it's the weight of the oil that can further tune how hard the clutch engages and how much air is moved.

I use a simple pot on the stove with a steamer basket in it to keep the clutch from touching the lower / hot surface of the pan. This is similar to how a double boiler would work and eliminates a hot spot causing the clutch from being hotter than the water.

I use a candy thermometer clipped onto the pots edge and roughly mid-water to get the water temp reading and avoid undue influence by the pot bottom which will be hotter.

The above may sound like a lot but it's easy/quick once the clutch is off the truck and split apart. As you see the clutch open under temps any confusion should be eliminated about how the clutch opens the ports, etc.

 

[WCBlueSky]

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offroad80s.com

Blue fan clutch mod...Thread has gone to hell, read at your own risk

History: On my first drive this summer after replacing my transmission I was having an overheat condition with the truck. On the following weekend while towing a camper it was real severe in the 230* range. After returning I was able to confirm that my Blue hubbed fan clutch was to blame...

forum.ih8mud.com

 

[77mustard40]

Just an FYI, on my FJ40 I simply replaced the oil with 10K cst and it made all the difference in the world. No other mod to the openings.

 

[1JZGTE]

Thanks for all the input guys, really useful, especially the threads that have been linked that I have been reading (including the big 50 pager!).

I have around 60ml of 7000 cst oil, not sure if that is overkill for our weather conditions here (25F winter to 95F summer)?

I am also tempted to test my fan clutch on the stove in some hot water to see where it opens up as standard, as per jpoole's response.

 

[Rifleman]

If i were doing this job I'd think about using a heaver weight oil then 7000 CST. Where i live it's not uncommon for members to run 20000 CST oil in their clutch. The day time temps here the last few weeks have been 110 to 115 degrees in the shade. So having a cooling system in tip top shape is a matter of survival here.

 

[1JZGTE]

Hi Rifleman. Out where I am, temperatures rarely go above 95F, and my Toyota is one of these:

Having reading the big 50 page thread ( Blue fan clutch mod...Thread has gone to hell, read at your own risk ) I note that 10 years ago people used 6 to 10k, but now 15k+ is common. I just wonder whether there will be any benefit in me putting in a high viscosity given that my car doesn't get punished as bad as some of the extreme offroading you guys do in your Land Cruisers in somewhere like Arizona where 100F is considered a cool day

 

[TomH]

Here in Seattle where temps rarely exceed 90F I've never run over 8K and never had a temp problem. I think you'll be fine with 7K oil.

 

[1JZGTE]

Thanks for confirming, Tom.

Before I pour the new fluid in, I'm thinking in terms of adjusting the temperature at which the clutch begins to engage, ideally I need to know at what temperature my thermostat engages, don't I? Because there is no point in the fan to be fully engaged before coolant is fully circulating through the rad. If the fan kicks in before the thermostat opens up, there will be no coolant to cool and I will simply be wasting engine power....

Am I right on that or no? I note that the recommendation is to have the clutch set to come on in at 95 degrees C.

EDIT: my thermostat opens up at 82 degrees C, so setting my clutch to begin engaging at 90 degrees C is probably ok?

 

[TomH]

I've never adjusted a clutch, only changed oil. I don't think adjusting is necessary in these milder climates. Ultimately it depends on how you use the car.

 

[WCBlueSky]

I note that the recommendation is to have the clutch set to come on in at 95 degrees C.

Actually Landtank uses 95 deg F, which is 35 deg C. But that is only for the lowest setting. It looks like your clutch has 3 settings from the picture.

 

[jpoole]

@1JZGTE

It will be hard for anyone to answer exactly what temp your clutch should open unless someone happens to have experience dialing in an equivalent setup.

The general concept that you don't want to over-engage the fan before the coolant is sufficiently circulating is a solid guiding principal but it's going to be a bit more complicated and hard to nail down. Keep in mind that the fan clutch is in air coming over the radiators vs. in the coolant circulating through the block. Also keep in mind the delay between when the coolant t-stat gets warm and opens and then when the air coming through the rad. is heated up in a relevant way, etc.

I'm sure my understanding is incomplete but allowing the radiator to try to cool at lower temps without heavy engagement of the fan seems like it will yield more efficient operation and save some HP in scenarios where the fan isn't really needed. Conversely, at the high-end of the acceptable operating temps you definitely want for the fan to be fully engaged to help the system avoid going to temps that are any higher. Finding the sweet spot between minimal fan engagement at cooler temps and full engagement at high temps is definitely possible but you may have to consider both oil weight and clutch temp/timing. To really dial this in you may need to change one variable at a time and then test/monitor through a useful range of temps/loads/etc... If needed you may want to add extra temp sensors to help figure out in real time when your t-stat is opening, what air temps are near the fan clutch, etc. All that's overkill unless you are really trying to dial in performance but could be fun if you are into it.

I added an odb2 bluetooth unit and watched my real-time temps closely in a variety of scenarios back when I was tuning the fan clutch on my 80. The 1fzfe in an 80 series can run hot at higher speeds ( > 70 mph ) and very low speeds if the fan clutch isn't setup right, per my testing at least. I first added heavier oil and then I slowly lowered the port opening temp on the clutch until engine temps stayed in a reasonable range most of the time. I think I was targeting 210 F as a peak temp under really tough conditions when I was making adjustments. As long as I don't overheat I'm just letting the lower-end of the temp range sort itself out. I rarely go over 200 F at this point but sometimes when towing in high heat/etc. it will get up near 210 F but that's rare. It took me a few months to tune my fan clutch as I don't drive a lot and would basically drive until I saw temps get too high and then make an adjustment. At some point no more adjustments were needed and I don't monitor that often now

A big question before you start making changes is how is the cooling system performing now? Are you running too hot in certain circumstances or pretty good overall? If you are pretty good I'd get a solid sense of your clutches current timing before messing with anything and I wouldn't make a dramatic shift from where you are now. If the LandTank numbers are close to what you have now you may want to try them or you may just want to change oil and get more data.

 

[1JZGTE]

Thanks for that, JPoole. The car is 25 years old, I have owned it for roughly half that time and until earlier this year there were no issues with the cooling. I change and flush coolant every 4 to 5 years and only use Toyota Red Coolant. Earlier this year, I noticed it began to overheat when sitting in heavy traffic, its fine when moving, so I think it must be the fan clutch. My first encounter was when I was waiting at a car wash, I wasn't paying too much attention until the dashboard displayed a warning and I saw the gauge climbing higher than I have ever seen it. Interestingly, iH8MUD is one of the very few places I could find much on this subject!

I split my AISIN fan clutch, heated in the oven and left it overnight to drain all the oil out. To be honest, there really doesn't seem much there, not sure if factory fill was minimal or whether over the lifespan of the car, the fluid simply evaporated.

I'm also taking TomH's point on board that in milder climates it might not be worth messing about with the timing of the clutch, so I might just see at what stage it engages, report back and if it isn't too high or low, maybe just leave it as is and dump a bottle of 7000cst in there and see how that works.

Will keep you guys updated!

 

[flintknapper]

I split my AISIN fan clutch, heated in the oven and left it overnight to drain all the oil out. To be honest, there really doesn't seem much there, not sure if factory fill was minimal or whether over the lifespan of the car, the fluid simply evaporated.

The silicone would not have evaporated, it's not prone to and the system is closed anyway (unless you have a leak). The silicone used is not a 'consumable' (like engine oil) so likely just a minimal factory fill. You don't want to overfill your clutch however or it will run the fan all the time. There needs to be room in the reservoir to take all of the fluid in the clutch (when it is not needed).

I'd wager 7K CST will provide an 'improvement' over what is in there now. Also Silicone Fluid degrades over time (from shearing forces) so having fresh fluid (along with increasing the CST value) should restore your fan clutch to like new (or better) condition.

 

[retrofive]

Similar temps here, I think I would at least use 10k CST.

 

[MidMan]

@1JZGTE

I saw the pictures of your opened clutch. It seems it almost running dry (without oil).

Just fill the Silicon oil in it, fix it back and it will be all good.

Plz pay attention while putting back the rubber O ring in the clutch. It should nicely sit there.

7000cst oil is good for you as you live in Europe.

Fan Clutches came in 3 colors (Grey, Blue & Red). Which one is yours ?

You don’t have to worry about adjusting the heat spring etc. Just fill the silicone oil and it will be all good. Its that simple.

 

[MidMan]

The silicone would not have evaporated, it's not prone to and the system is closed anyway (unless you have a leak). The silicone used is not a 'consumable' (like engine oil) so likely just a minimal factory fill. You don't want to overfill your clutch however or it will run the fan all the time. There needs to be room in the reservoir to take all of the fluid in the clutch (when it is not needed).

I'd wager 7K CST will provide an 'improvement' over what is in there now. Also Silicone Fluid degrades over time (from shearing forces) so having fresh fluid (along with increasing the CST value) should restore your fan clutch to like new (or better) condition.

Here in Lahore we have temperatures like 30 to 45C Starting from March till End-October.

By End Dec./Jan. the temperatures become like 15-20C and we call it winter.


The previous owner of my truck (2 years ago) was using black fan clutch with 5000cst oil. And truck was not good to drive in city traffic during day. It start overheating.

I changed the fan clutch as “RED” filled it will 12500cst oil and no more heating issue since then.


And when I opened the previous fan clutch, then obviously it has no leaks. But oil was almost non-existent too. I filled with 5000cst oil and fix it back. The situation improved, but not much.

I replaced it with red clutch and 12.5K cst oil. And now it has no issues during hot summer day while waiting at red signal to turn green.

 

[richardlillard1]

Given the amount of shearing area that clutch has, it’s similar to the black hub, which typically runs a much lower cst silicone than the others available for the 80. Can’t comment on how your car will do, but I would say around 12.5k cst fluid should be more than sufficient.

I don’t like using water to tune the valve. A heat gun and a thermocouple is going to produce more consistent results. That said, at this point, the clutch has been on the vehicle for how long? I would think the operating temps of the clutch have been well proven by this point so I wouldn’t fuss with it.

Drain it, fill it, see how it does. I’m betting it will be fine with fresh fluid.