Flex Fan

[JK McDonald]

Well after a two year series of retrofit and repair on the engine and transmission, fuel injection issues, electrical problems, interior upgrades and heating/ac problems - Miss Purdy is finally completely back together and running down the road great. As long as I keep air flowing through the radiator the temperature gauge stays in the middle even with the A/C on but once my ground speed is 0 the temp quickly climbs and turns on the electric fan. The timing , radiator and water level all checked good.

I have eliminated the air pump, added a toggle switch to manually control the electrical fan and successfully refilled the clutch with silicon oil to no avail. The bimetallic strip is installed correctly and there are no leaks even after adding more silicon oil to make sure I had put in enough fluid. The fan clutch just turns too freely once it is hot. After trudging through every heading I could find on the subject, surely there must be a less expensive and more reliable option to another fan clutch. Has anyone ever found a flex fan that will fit ?

Thanks, Michael
I have a little more information and an update to a couple of tests made to the operation of hydraulic fan clutch. If you remove the center pin that is under the bimetallic strip - it will measure approx. 9mm in length and .8mm thick. Assuming your radiator is in good condition, you've added enough silicon oil inside the clutch and your aged bimetallic strip is operating reasonably well, adjusting the length of this pin can be the key to the engagement or coupling up of the fan to the engine driven pulley. With a little experimentation I determined that if you shorten the pin by .5mm the fan not only begins to engage slightly earlier but satisfactorily moves much more air in relation to the sensed air temperature coming through the radiator. The removal of .25 mm from the pin in several increments continued to make significant changes to the cooling performance of the hydraulic fan but as you approach 1mm I feel the lockup was then too early.

NOTE: Instead of modifying your original center pin, use the solid end of an old drill bit that is approx .8mm thick. I used a harbor freight digital micrometer and a fine-grained grinding wheel to help keep track of the length of the new pin being made. Save the original pin in reserve incase of a MM (major malfunction). In order to make sure the center rubber cap seals everything up I used a drop of clear sealant on the pin tip just before the final installation of the bimetallic strip. After a couple of weeks in the Texas July heat, this seems to have helped Miss Purdy – (84 Red/Blk Interior)– good luck….. Michael

[redrider044]

I have an extra 928 Porsche fan clutch shaft & an old Pontiac water pump. I'm trying to find a machinist to install the fan mounting flange from the Pontiac waterpump on to the Porsche fan clutch shaft without costing a small fortune. As soon as I get it done, I'll post my results.

[m21sniper]

Just add a second electric fan.

[redrider044]

After reading a lot of the posts here on Pelican, I was under the impression that electric fans that produce any meanful cfm, pull too many amps on start up for the stock electrical system, thats why I'm going the flex fan route. Also, I like to keep things as simple as possible. I found a local machine shop here in New Jersey that told be the machine work can be done for about $100. I'm seeing the owner tomorrow. If it works out, I'll post the results along with his company' contact information. I'm keeping my fingers crossed.

[m21sniper]

They don't. I've been running 2 electrics on my bosch alternator for, oh....5 years.

I don't even have a clutch fan installed.

BTW, flex fans suck down a butt-load of hp. You'd be far better off just getting another stock clutch fan.

[surfdog4]

did you flush the radiator? when i had my radiator re-tanked they flushed it and got much better flow through...