Viscous fan hub coupling for the 80 series diesel

[StuCruiser]

Hi all
I’ve read every posting on the forum I believe relevant to the fan coupling oil refilling including the mammoth 50+ thread from @landtank and others, and that has been going on now for seems as many years These have been very helpful indeed but I haven’t quite got answers to a couple of questions. I’ve also posted a heap of photos below in case it helps others in the future.

I acquired a spare viscous coupling. I got a spare fan from a wrecker and they gave me the coupling at the same time, so this is a spare that I’m servicing. When I opened up the two halves it is different to the majority of the couplings seen on the forum which are mainly petrols. Instead of it having 2 little round holes which “open” and “close” as the bimetallic strip moves across them this one has small rectangular holes within the vanes and then additional holes which form L shapes (don’t know how else to describe them!). From reading this style appears to be the “older style” and be known to be very efficient.

The 2 halves separated and draining:

Dirty oil, the small holes within the vanes and the L shaped holes:

More sludge to remove and clean from within the resevoir:

Total amount of oil drained less the odd ml in rags. I don’t have a way of measuring it but I’m estimating 15-20ml:

Now on to my first question. I did some testing to see when my valves opening go through the 4 stages: fully closed, half open, 3/4 open and fully open. It’s mid 20 deg C in the workshop today. What was interesting straight away was that the small holes within the vanes didn’t close (see screwdriver tip). There is potential for them to close, I guess I need to stick ice on the bimetalic strip but I was surprised that these vane holes will remain open all the time allowing oil into them on pretty much every day, unless I’m in the snow. Does anyone have any data on this please ie at what temp should these vane holes open or close? L shaped holes shown fully closed (see wood screw):

 

[StuCruiser]

Here’s the potential for the small rectangular holes in the vanes to close, the gap still to go, but the bimetallic strip needs to cool down below ambient of 24.5 deg C:

Right, now on to the testing. This was done with a hot air gun and the IR temp gun you see above as I don’t have a waterproof thermometer. I don’t know if that makes a difference. The bimetallic strip was heated up until the L shape holes fully opened and then the readings captured as it cooled back down. I recorded fully closed, half open, 3/4 open, fully open.

This was 3/4 open:

This was half open:

Fully open and fully closed are self explanatory.

Here are the results:

I discounted test 1 as it appeared off and I also found more sludge to clean out of the reservoir (this also made what I thought was bearing noise disappear).

Anyone have any comments on this? Adjust it? Leave as Is? Same as yours?

Lastly where dId you fill up to with the fresh oil? The black stick, blue pen or red toothbrush?

Thanks for any help…

 

[StuCruiser]

Oh I also found this but I couldn’t understand his table where he says “all at half open”:

Tuning and Understanding your Toyota Viscous Fan Clutch

Landcruiser or Hilux overheating? Your factory fan clutch is probably under-filled and incorrectly set from factory. Fix this first and you may save a lot of time chasing issues. (4 Runner or Tacom…

neuralfibre.com

Link here
I think he says he filled his up to a few mm below the blue pen?

 

[jellis]

You are in NZ so not much in terms of temp extremes, you are probably over-thinking this.

It doesn't matter where you fill it, look at that last link and you'll see a pick where he flips up the disc so you can see the contiguous reservoir underneath. It all goes to the same place, eventually.

IIRC the adjustment was for the part in the outer rings to be 1/2 open, not the L shaped slot. The part in the outer rings is when the fan BEGINS to grab, that's all you are adjusting here.

You need to use a water bath and heat soak the entire unit to set the temp.

 

[StuCruiser]

You are in NZ so not much in terms of temp extremes, you are probably over-thinking this.

It doesn't matter where you fill it, look at that last link and you'll see a pick where he flips up the disc so you can see the contiguous reservoir underneath. It all goes to the same place, eventually.

IIRC the adjustment was for the part in the outer rings to be 1/2 open, not the L shaped slot. The part in the outer rings is when the fan BEGINS to grab, that's all you are adjusting here.

You need to use a water bath and heat soak the entire unit to set the temp.

Thanks for that. Yes, the one I have in the vehicle currently works very well with engine temps consistently running at 80-82 deg C (176-179 deg F), but very occasionally in our hot weather here (97 deg F), 35” tyres, engine mods, full AC, mountain track, towing etc I’ve seen >200 deg F. I’d like this spare to be spot on.

When I mentioning filling I meant up to which level, sorry, rather than where do I pour the oil in. Obviously if I overfill it it will be on all the time.

Setting the adjustment for when the smaller rectangular hole in the rings opens makes sense, thanks. Mine is obviously set to an opening temp of less than 25 deg C (77 deg F). I’ll chill it and see what that is.

I’ll need to find a water bath and a temp sensor…ugh. It makes that much difference? I suppose I’m just heating mainly the bimetallic strip whereas a bath heats the whole front of the hub.

 

[StuCruiser]

And I still don’t understand this table. Can anyone explain it to me please?

I’m guessing the 4 stages are the same as what I’ve posted above - the movement of the strip opening the holes. “Closed” being the small rectangular hole in the vanes being closed and stages 1-3 referring to the L shaped one?

But what does “all at 1/2 open mean”? That doesn’t make any sense to me. What is half open?

 

[jellis]

In 105F+ ambient I routinely see 220-230F engine temps while climbing mountains with a trailer. No bueno. I had to switch to a 4-core AL radiator to make a significant difference, this fan hub adjustment didn't make as big of a difference as I had hoped. I think I did 35k fluid by mixing 20k and 50k.

Basically the downside of having it locked all the time, AFAIK, is that your rig will take longer to warm up in cold weather and you might lose a bit of fuel economy due to unnnecessary fan drag. But the benefits are lower overall engine operating temperature which is really important....so benefits massively outweigh downsides to me!

 

[StuCruiser]

If I saw 230 deg F on my gauge I would be totally sh1tting myself! That’s way too hot for my liking.
Putting in high viscosity oil and lots of it will definitely give you lots of fan and yes, you’re right, at the expense of a bit of lost fuel economy. I’m not too bothered about that as mine 80 will never be fuel economical.
But I’m a believer in that you can have the best of both worlds, a “tuned” cooling system, that will give you full noise cooling when you need it and not so much when you don’t.

 

[StuCruiser]

I borrowed a digital temp gauge so I could re do the test. Can confirm it does make a bit of difference compared to the hot air gun. Here’s the results:

So this coupling is fully open at 45 deg C. I’d be really keen to hear from anyone else that has done this. Don’t be shy!!!

Because it seems to be set so low I really struggled to record when the small rectangular hole opens/closes. I had to put ice in the water bath to try to get it to close and by then the tolerance of the bimetallic strip is very low so I’m not at all sure the numbers that low are accurate.

Whilst I was doing this it did get me thinking. The only number you’re really interested in is when would you like your fan to be fully open ie on full bore giving as much cooling as possible. The rest you can’t change anyway. Obviously the coolant temp is always going to be higher so the number needs to be lower than that but how much lower? If you go too low then it’ll just be on unnecessarily, which isn’t the end of the world.

 

[StuCruiser]

Not getting much interest so I’ll bring this thread to an end (I must be breaking new ground ).

I’m going to compare this spare fan coupling with values on the one on my vehicle, which works well, and go from there.

 

[mudgudgeon]

Whilst I was doing this it did get me thinking. The only number you’re really interested in is when would you like your fan to be fully open ie on full bore giving as much cooling as possible. The rest you can’t change anyway.

I followed the guide you have years ago.

It made a difference for my cruiser at the time, until the oil leaked out

I think when it starts to open, and when it's fully open are both important. Similar to the thermostat in your cooking circuit

 

[ToyotaMatt]

doesn't AMAZON.NZ have these AISIN blue box units new for you blokes down these in OZ ?

seams like a lot of messy mess there Mate ?

 

[jellis]

They aren't necessarily tuned this way from the factory..... This is a tweak to the factory setting, just like adding more viscous oil.

IIRC all you can do is rotate the plate, so there is only one adjustment to be made.

 

[Stiles]

Rebuilding is cool. Tinkering is why most folks have these trucks. That said...