Restoring An Original C2 Fan Clutch

[Joe S.]

I have an original, 67-dated big block Schwitzer (bar-type) fan clutch that unfortunately, was stored face-down causing the fluid to leak out of the front plunger. Referencing "Fan Clutch Cool Down" (Restorer Winter 1991) and "Corvette Fan Clutches" (Restorer Spring 2005), it would seem that you could refill the reservoir by removing the rectangular bimetallic plate and brass actuator plug, depressing the valve and refilling the reservior with a high quality silicone hydraulic fan clutch fluid (Toyota Part number 08816-03001). A variation of this procedure is well known for the sealed Porsche 928 fan clutch. See http://www.nichols.nu/tip482.htm

Has anyone ever tried this?

[Pat K.]

Re: Restoring An Original C2 Fan Clutch

I'm sure Fred Oliva can answer your question. He does clutch fan restoration.

foliva@gate.net
954-755-1161

[Joe S.]

Re: Restoring An Original C2 Fan Clutch

Fred was quoted at the bottom of the thread on the weblink in my first post as saying:

"The biggest problem with the procedure described is getting the correct amount of fluid back into the clutch. The best way to determine this is to add about 5 cc of fluid with a syringe as described, and then test to see if the clutch functions. If it does not, add another 5 cc & repeat. The basic test for function is to shut the engine down at idle & observe the fan. It should stop within 3- 5 revolutions of the engine stopping. This process is labor intensive, but it is the only way to get the correct amount of fluid back into the clutch. The caveat here is that if the clutch was low on fluid, the ceals are probably bad & the fluid will leak back out in a short time."

Mercedes also uses a bar-type clutch that is refillable with a similar procedure:

http://www.mercedesshop.com/shopforum/showthread.php3?t=89145&page=1&pp=15

I have attached pictures of the Corvette-Schwitzer, Porsche and Mercedes clutches for comparison.

In addition to the Toyota silicone hydraulic fan clutch fluid (#08816-03001), good quality silicone oils are also available from NAPA and from hobby shops for use in the differentials of radio control cars. Here is a link with great pictures of how to refill the Porsche fan clutch: http://members.rennlist.com/blueshark/page12.html

I will attempt to refill my clutch using this procedure and will update this thread with the results.

[Joe S.]

Re: Restoring An Original C2 Fan Clutch

After a couple of nights of surfing the net and an hour long conversation with an engineer at the OEM manufacturer (Schwitzer now Borg Warner Turbo Systems), I finally tackled refilling the clutch. Long story short- it works great!!!

You can purchase fan clutch oil at your local Toyota dealership (part number 08816-03001) and high quality 3000 cst (centistokes) silicone oil at hobby shops that carry parts for radio control cars. Toyota sells 6000 and 10000 cst clutch oil (part numbers 08816-06001 and 08816-10001), but I figured that the lower viscosity stuff would probably be more forgiving when it came to how much you filled the reservoir. The radio control car differential oil comes in a 50ml bottle for ~$7, more than enough to do a single clutch. The Toyota clutch oil is $15 for 18ml. I went the cheap route figuring I could always drain the clutch and refill later if I didn’t like the results.

Schwitzer’s tolerance spec for filling their clutches is 4cc so the recommendation to fill the clutch in 5ml increments is right on. I probably overfilled the reservoir, but since I only plan to use it for Flight Judging, I don’t care if the clutch is a little tight, as long as it keeps the car cool at idle.

Since the Corvette Eaton spring-style fan clutches, must be stored shaft-side up to prevent them from leaking, you might be able to use this same procedure to refill them at the shaft bearing. I guess you could even drill and tap a small fill hole in the aluminum body of the clutch (A clever restorer could make the plug nearly invisible).

There’s no substituting an NOS clutch or a professional rebuild but if your clutch has good bearings and seals, this is a pretty cheap way to get the real deal for Flight Judging. When in doubt, install a new fan clutch and always use a new fan clutch on a car you are going to drive. I would be interested in hearing from anyone else experimenting with refilling either of these clutches.