jaluhn83
Full Access Member
As some may remember I recently completed an engine rebuild and upgrade but on my first good test drive I suffered from the infamous dead fan clutch problem and had to limp back home. This was quite frustrating as I had what seemed to be about the only solid functional idi fan clutch - it would lock up solidly by about 210* and was very effective in engine cooling. Since time was an issue I wound up buying a new OEM clutch but was not happy with the higher engagement temp and what seemed to be a less effective lock up - I think a midget with a small chinese fan duct taped to the bumper might have almost been more effective. 
So I started thinking and doing some research since it seemed like the only thing wrong with the old clutch was that it was low on fluid - surely there'd be a way to refill it. Turns out there is. I found several articles referencing a 1975 Toyota TSB that covers refilling the fan clutch and adapted the procedure a bit. It's rather more guess and check, but it seemed to work.
The toyota tsb references 3 part numbers: 08816-03001, 08816-06001, and 08816-10001 for 3,000, 6,000 & 10,000 Cse (a measure of viscosity- higher is thicker) fluids. It is unclear which is the correct viscosity, and the quantity is also a question. Somewhere I found mention of 50 cc, and this is what I used but it appears that this may have been too much based on performance. I would try ~30 cc. Apparently the Toyota fluid is quite pricey, but I also found a reference that said that rc car shock or differential fluid was essentially the same thing, so what I wound up using was 10,000 Cse rc car fluid - it was $4 for a 50cc bottle. I'd thought shock oil would be closer to what was originally in there, but the stuff I wound was speced in SAE oil weights (ie 30wt) rather than Cse and I didn't mess around with converting, just got the silicone differential oil.
The procedure to refill is quite easy. The other articles I found discussed removing the center spring and pin and using that hole, but I couldn't get it to come out easily so I drilled a hole in the front face about 1 1/4" out from the center. On my clutch there was a small (~1/8") hex bushing here that I thought might have been the original fill plug but now I'm not sure since it seemed to be cast in. It worked well though. There was about a 1/4" deep space behind there that appears to be circular and could be drilled into anywhere. I suspect this is the return cavity.
Once the hole was drilled it was a simple matter to use a small syringe (left over from horse vaccines, might be able to get one from the drug store or local feed store if you don't have one already) to pump the oil into the clutch. Once I put all the oil in I found a sheet metal screw that looked like it'd fit well and cut it off to about 1/4" in length, then coated in in RTV and screwed it in.
And the results: The repaired clutch does now work. In fact it works too well - it never completely disengages now. I suspect I used too much or maybe too thick of fluid. ;p This is much better than not working at all though. I still plan to convert to an electromagnetic clutch eventually, but I am very happy with how this worked out and figure others on here can benefit.
The $64 question is of course how long it's going to last. I think in most cases these clutches fail from gradual leakage over time, so refilling them should extend their life quite a while. If there's a more serious leak though life will obviously be shorter. Likewise if there's some other failure in the clutch. I would bet that 75% or more of the failed clutches could be fixed this way, at least to get some more life out of them.
So I started thinking and doing some research since it seemed like the only thing wrong with the old clutch was that it was low on fluid - surely there'd be a way to refill it. Turns out there is. I found several articles referencing a 1975 Toyota TSB that covers refilling the fan clutch and adapted the procedure a bit. It's rather more guess and check, but it seemed to work.
The toyota tsb references 3 part numbers: 08816-03001, 08816-06001, and 08816-10001 for 3,000, 6,000 & 10,000 Cse (a measure of viscosity- higher is thicker) fluids. It is unclear which is the correct viscosity, and the quantity is also a question. Somewhere I found mention of 50 cc, and this is what I used but it appears that this may have been too much based on performance. I would try ~30 cc. Apparently the Toyota fluid is quite pricey, but I also found a reference that said that rc car shock or differential fluid was essentially the same thing, so what I wound up using was 10,000 Cse rc car fluid - it was $4 for a 50cc bottle. I'd thought shock oil would be closer to what was originally in there, but the stuff I wound was speced in SAE oil weights (ie 30wt) rather than Cse and I didn't mess around with converting, just got the silicone differential oil.
The procedure to refill is quite easy. The other articles I found discussed removing the center spring and pin and using that hole, but I couldn't get it to come out easily so I drilled a hole in the front face about 1 1/4" out from the center. On my clutch there was a small (~1/8") hex bushing here that I thought might have been the original fill plug but now I'm not sure since it seemed to be cast in. It worked well though. There was about a 1/4" deep space behind there that appears to be circular and could be drilled into anywhere. I suspect this is the return cavity.
Once the hole was drilled it was a simple matter to use a small syringe (left over from horse vaccines, might be able to get one from the drug store or local feed store if you don't have one already) to pump the oil into the clutch. Once I put all the oil in I found a sheet metal screw that looked like it'd fit well and cut it off to about 1/4" in length, then coated in in RTV and screwed it in.
And the results: The repaired clutch does now work. In fact it works too well - it never completely disengages now. I suspect I used too much or maybe too thick of fluid. ;p This is much better than not working at all though. I still plan to convert to an electromagnetic clutch eventually, but I am very happy with how this worked out and figure others on here can benefit.
The $64 question is of course how long it's going to last. I think in most cases these clutches fail from gradual leakage over time, so refilling them should extend their life quite a while. If there's a more serious leak though life will obviously be shorter. Likewise if there's some other failure in the clutch. I would bet that 75% or more of the failed clutches could be fixed this way, at least to get some more life out of them.
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I would store it sideways - same orientation as it is on the engine. 
