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Old 08-28-1999, 04:38 PM
VA300SD VA300SD is offline
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Join Date: Jul 1999
Posts: 239
Temperature controlled Viscofan coupling for the main engine fan should also be looked at. This temperature sensitive arrangement causes the engine fan to engage and increase its RPM proportionate to the engine RPM, but not to exceed 3500 rpm.
When not engaged, the fan RPM isn't supposed to drop below 2100 RPM.
Anyway, this fan clutch deal is oftentimes overlooked, causing folks to suspect perfectly good radiators, thermostats, aux. fans, and many other expensive stuff and still scratching their heads over overheating problems...
This fan clutch problem applies to many other brands. I mention this because I've noticed whenever there is an overheating discussion the fan clutch is often left out as suspect and I learned the hard way with my Volvo.

According to the engine manual, testing involves revving the engine at 4,000-4500 RPM and wait for the coolant temp to rise to 90-95C, at which point the fan clutch will engage and increse the fan speed by about 1000rpm, which should be noticeable by the different pitch of the fan rotation. (I'm guessing they're not suggesting you rev up the engine from dead cold and maintain that until reaching 90-95C....)
They also mention this is not a rebuildable part and needs to be replaced.
Another interesting point is the coupling has to be transported and stored vertically and should never rest on its front end if it needs to be laid down during assembly.

[This message has been edited by VA300SD (edited 08-28-1999).]