Viscous Fan - PeachParts Mercedes-Benz Forum

BDBENZ · #1 07-25-2004, 01:34 PM

My viscous fan roar, especially with the top down, is certainly annoying. I have searched many of the posts, so I believe that the fan at least works, but is it working properly? At a steady 1500 RPM the fan constantly engages and disengages. I get the roar and then peace and quite. This repeats approximately every 20 seconds. What would cause this?

Thanks

BD

deanyel · #2 07-25-2004, 02:27 PM

Are you sure it's the viscous fan making the noise and not the electric fans. On my 124s it's the electric fans that make noise.

Kebowers · #3 07-26-2004, 12:11 AM

20 sec sounds auwfully rapid for the viscous clutch to cycle on the fan. The fan WILL make a lot of noise when it kicks in--its job is to move a lot of air. It maybe the radiator core is mostly plugged and you reallyhave only a few tubes working. In that case, the fan will quickly 'see' cool air when it engages and will quickly cycle off. If you confirm it is the viscous fan, and not the electrics,I would raise the suspect level on the radiator to the top of the list.

Take it out and have it rodded out by a good radiator shop (a good one will have the crimping jig necessary to remove the top and bottom tanks. ) Cost less than $100.

BDBENZ · #4 07-26-2004, 02:00 PM

Sounds reasonable, I will check the radiator for hot and cold spots this evening. This would make since, the fan acts normal otherwise.

Thanks BD BENZ

cbdo · #5 07-26-2004, 08:32 PM

I've got the same phenomenon, and it's persisted unchanged after a new radiator (done for other reasons). I'm convinced that what happens is the viscous drive degrades a bit over time and no longer waits until the temp's risen much before it engages. It doesn't impair the cooling performance, as the final result is the fan engages *more* than necessary at cooler temperatures, not *less*. I'm betting you notice it especially when the engine isn't fully hot yet, and when the weather isn't too hot, as the drive locks up with increasing heat so the cycling stops and it stays constant-on. BTW, the sound pattern clearly rules out the electric fan(s) as the source.
The fan itself, as far as sound created by the blades in motion, is notably noisy. I've known one 107 owner to switch to a later and quieter fan and DIY the shroud modifications, with a reported reduction in the noise level. I've also seen several posts from folks who replace the belt-driven fan altogether with electrics, which also involves a bit of reengineering. The immediate remedy would be to replace the viscous drive, which is on my list of when-I-get-a-round-tuits.

BDBENZ · #6 07-26-2004, 09:46 PM

Thank you for relating your experience, my radiator seams to flow well with even temps. You are correct in your summary of how the fan acts in the cool weather. It has been rainy and in the 60's here all week, and the fan is more noticeable with the constant cycling. I would like to go to elec. fans and am considering a spal fan with thermostat. I understand that the newer model are going to electric. I will also look into replacing the clutch.

Thanks,

BD

brewtoo · #7 07-26-2004, 10:32 PM

Quote:

Originally posted by cbdo
I've got the same phenomenon, and it's persisted unchanged after a new radiator (done for other reasons). I'm convinced that what happens is the viscous drive degrades a bit over time and no longer waits until the temp's risen much before it engages.

Hmmm....In my experience, when the clutch fails it no longer engages well and hence never really comes up to speed.

But that's just my experience.

cbdo · #8 07-27-2004, 10:46 PM

I know it seems a bit counterintuitive, but I can't think of any other explanation for the way this behaves. I'll try to remember to post an update when I eventually get the replacement done.