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DIY/ tips for Installing an RB25 R33 Clutch fan into SR20

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So I figured I would do a quick write up on this as there wasn't much info I could easily find when looking to upgrade the fan on my SR20. If this has been covered - Feel free to delete.


The 9-blade RB25 fan from an R33 is a direct fit to an SR20. You retain the standard shroud and everything and it is a GREAT upgrade. You immediately notice the huge improvement in airflow after this is bolted up.


The temps in my s15 started to go up as the season started heating up (86deg at max on highway cruising at 3k rpm vs 82 during winter...). Anyways, getting the car ready for some track work etc I figured this would be a good upgrade.


The going price for an RB25 fan with the clutch in tact is roughly $80 and is worth every cent... I recommend buying it with the clutch as you can just undo those 4 nuts that hold the old clutch and fan in place, pull the old assembly out and replace with the new fan assembly. Plus the RB25 clutch has 6 coils on the front and the SR only has 3 (no idea why or what the difference is but I'm sure it's there for a reason)


Basic steps.

  1. Remove the intercooler piping and lines running to the intake/throttle body - you will need the space to remove the fan and install the new one.
  2. Loosen the 14mm nut at the front of the alternator holding it in place and then loosen the 12mm pretensioner bolt at the side to relieve tension on the fan belt. - You need to do this as the fan belt is VERY tight. Once you remove the fan the pulley loses structural strength and will actually warp from the stress. If you try to put the new fan on you will notice that it will not go up snug against the hub - this is due to it warping... Spend an extra two minutes doing this and save yourself the hassle later....
  3. Undo the 4 10mm nuts holding the old fan and clutch assembly onto the pulley. Ratchet spanner works the best. DO NOT use a shifter - You will easily round the nuts in under a second....
  4. Have a friend pull the fan shroud toward the front of the car to give you a bit of space and pull the fan and clutch out (Use the extra space made in front of the throttle body to get the clutch out as it needs more space than the fan).
  5. Once it's out reverse the procedure with the RB25 fan and clutch (It's a TIGHT fit but it goes in. It's easier than removing the old fan...)
  6. Re-do the nuts that hold the fan in place, re-tension the alternator and make sure the fan belt is nice and tight (not too tight) and fix exerything else up nice (DO NOT over tighten the nut that holds the alternator in place from the front. It WILL snap with too much force. It doesn't need to be too tight...).

My temps are now 77-78 during normal driving and 82-83 on the highway cruising at 3k in heat (The thermostat only opens at 76-77 degree so it can't get only colder :) ). VERY useful upgrade - especially in summer :). You will feel the difference immediately once you start the car with the new fan :)


I didn't use too much detail above and pics shouldn't really be necessary as it is very straight forward but hopefully this thread will help anyone else looking for information in this upgrade :).

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Can anyone confirm if you really need to lessen the belt tension(and risk messing up the tension when redoing) prior to replacing the clutch fan?


The water pump and thermostat were replaced last year - foolishly didn't replace the clutch which has now gone.

I was expecting to just follow the manual which when replacing the water pump mentions disconnecting the clutch fan etc prior to loosening the belt and pump removal.

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