The Howling...Fan drive?

[cbdo]

I think I've got some form of issue with the viscous drive for the fan on my '89 560SL. It's running fine with no overheating, but there's a noise on the order of a mild howl or moan, definitely changing with RPM but not always directly. When cold and moving at say 35-50 it will rise and fall in pitch even at steady RPM; when hot, it runs directly with RPM. It's louder sometimes than others, and not always noticeable at an easy cruise (say 45 or so).
I can't think of anything other than the fan that won't tie directly to either motor speed or vehicle speed. If as I suspect this is the fan drive, is it telling me it's about to fail, just making noise, or something in between? Does it need replacement, or is it capable of being refilled as an archive thread describes for a newer model?
TIA-

Craig

[cbdo]

FWIW, with the engine off the fan turns easily by hand, either hot or cold.

[Q]

Check that your fan blades are not running against the shroud. If they are, your engine mounts have sagged and need replacement. Some shrouds are held on by clips that you can adjust to move the shroud down a bit as a temporary solution.

[cbdo]

Thanks for the suggestion, Q. The fan blades are clear of the shroud, and the sound doesn't suggest anything hitting anything.
It's clearly audible over normal engine and road noise, but not truly loud, and has a definite pitch that varies more or less closely with engine speed--but when cold, the pitch will vary even at constant engine speed.
My main questions:
Are there conditions when it's normal for the viscous clutch to cycle somewhat?
Is there anything other than the fan drive that would sound like this? (I can't think of anything.)
Is the fan drive on my car is the same as discussed in this thread:
Clutch Fan on 300D 124 viscous oil&pagenumber=1

[psfred]

Craig:

Normal. My Volvo sounds like a jet engine, really howls (so does the turbo).

You should be getting the sound on startup for a few seconds, maybe longer.

As the temp of the air off the rad changes, the fan will go on and off -- when off, the fan turns arou 800 rpm, more less independent of engine speed. When it's on, it will turn up to 3000 rpm or so, directly dependent upon engine speed.

It will come and goe in traffic, even on the highway if you are in traffic and speeding up and slowing down a lot -- the Volvo used to come on and off in Cincinnatti when I drove through there -- the combination of heavy acceleration and intermittant slowing down would kick it on, AC or not.

Peter

[cbdo]

Peter, thanks for the illumination! I just realized how long it's been since I had a vehicle with a mechanical fan, rather than electric-only--and immediately after that, how long it's been since I had a vehicle with the engine mounted fore-and-aft.

[psfred]

One does tend to forget.

I'm going to scare the s.... out of passengers in my cars soon, though -- my work car is a manual tanny, and I'm already back into the habit of putting the clutch in at stops -- OK on the 280 SE since it has a narrow brake pedal, but I'm gonna catch my foot in the 330D or the Volvo sometime and toss everyone on the floor....

Peter

Craig
Just having issues with my viscous fan on 560sel. I put a new one in 3 years ago and only have 7000 miles on it and it is gone again. From experience this is how the fan SHOULD work:
CAR COLD- on start up the fan will appear to be locked up and howl for a few seconds when you rev it - then it slows down and spins at idle speed even if you rev the engine again and again.
ENGINE HOT - when your temp. guage shows about 85C or higher - the fan's bi-metallic strip will bend from the heat and allow the clutch to engage so the fan will howl when you rev the engine. That is normal.
If the fan howls all the time when you rev the engine -hot ot cold - it is defective. If the fan does not howl when you rev the engine when hot (my case) it is defective. My new viscous clutch arrives tomorrow so I can play with the old one to find out why it failed. Mine was working great until one hot day when I noticed the engine temps climbing to 110C on the highway. Revving the engine in neutral caused the temp to climb to 115C and the fan would not lock up - I took a gloved hand and even turned it in the opposite direction at idle. Normally - if the fluid leaks out - this is the result. However if the fluid had leaked out of mine - it would not spin and howl for a few seconds at cold start up - which it does - then slows down and never speeds up again. I suspect a bi-metal problem but don't want to play with it until I have a new one installed. I will post my findings if the old one can be fixed.

[cbdo]

Thanks, moedip; at least for my mechanically basic mind, that's the clearest rundown I've seen on what to expect if it is indeed healthy. Based on that, I'll double check but may well try replacing it (which appears to be within my skills--four simple bolts and transplanting the fan to the new drive, is it not?). I'm not overheating or even close, but the sound is mildly annoying to a mildly obsessive owner.

[psfred]

I think I actually heard the 280 SE lock up today with the AC on -- a first. The temp gauge was normal for once, too -- maybe the pin was stuck or something.

Noticable turbine noise, even over the bad exhaust noise from the cracked manifold. Need to do something about that someday.... have the new manifold but am too lazy to tear into it.

I'd learn to live with the sound, a new clutch isn't going to change the noise. Just the way a Benz is!

Peter

[william rogers]

can't hear the fan for the induction noise on my Euro 500 SE when in passing lanes in mt's he he!
Peter, just putting my manual 74 240 D back on road after two years being side lined, my other three cars are automatics, bet I'll foot fumble for a while, but look foward to driving the old girl again.........
william Rogers

74 240 D
81 SD
86 Euro 500SE with Euro 420 engine
(geared so high marks on speedo for third to forth are just under 140)
81 2wd K5 Blazer 454 onversion,still a little big block Chevy blood in this old MB head.......

Put the new fan clutch in yesterday. Car cold - fan roars for a few seconds and drops to lower spin. Car hot - noticed something I never noticed before with the old clutch. As the engine temp climbed to 85C the fan still lazily turned - even if you revved the engine. When the temp hit 90C - you could hear the fan speeding up - when the engine was revved the fan roared. The roaring continued for about 10 seconds and the fan slowed down again - the temp guage was down at 85C! Keeping the engine at about 1500 RPM I sat and watched. The engine temp climbed to 90C - the fan roared - the temp dropped to 85C - the fan slowed down. This cycling continued with the engine temp varying between 85C and 90C - max. It really was amazing to see the fan roar and the temp drop so fast. I can't say I have seen this with my old clutch as my car always ran between 85C and 103C depending on conditions. Sometime soon I will take the old clutch apart and find out what failed on it - though I am positive it will be a sticky valve or bad bi-metal strip. Hope what I noticed with the new clutch is of some help to others. By the way - related topic - when my bad clutch allowed the car to get hot - my aux fan did not kick in until engine temp hit 107C - then ran until the engine temp dropped to 100C. So to those who think their aux fan does not work - wait until your engine temp is 107C and see if it cuts in before thinking it is not working. From what I have learned - it is only a backup if the viscous fan cannot handle the load to keep the engine below 107C. Tonite I work on the hydraulic system groaning proportioning valve.

[placo1]

Does anyone know if the 500E Viscous Fan operates in the same fashion?

[psfred]

They all do, that's what they are supposed to do.

Peter

Just thought I would update my high heat problem. At the end of July I had the dreaded broken neck on my rad. Changed the rad and the engine temps climbed to over 110C. Changed the viscous fan (new one just put in 3 years ago - only 7000 miles on it) and the temps stayed below 95C even on days with 90-95F outside temp on the highway. However - with the A/C on the temps still climbed to 105-108C. At 107C - my aux fan kicks on and holds the temp there. I added a bottle of Red Line Water Wetter to the rad and the temps always stay below 100C now even with the A/C on. Had a real hot muggy Sunday last weekend temps were about 98F with high humidity. Took the car on the highway for a 2 hour run at 100kph - the highest the temp got was 101C - while we were freezing with the air on full to test the loading on the engine to try and get the engine to overheat. I now am happy with the cooling I am getting on the 560sel. It appears that the viscous fan I put in 3 years ago was not up to snuff since new as now with the new one installed with the Water Wetter - I see a noticable difference in the high side engine temps - they are a lot lower. I haven't had this car running this cool for 3 years. As I drive the car now - when the engine temp hits 95C - you can hear the viscous fan howl until engine temp hits 90C then fades - my other fan did not do this. On real hot days when the engine temp is over 95C - the fan howls to keep engine cool - it works as it should. Hope this can help others with the notorious high heat syndrome.