Locking engine fan "ON" - PeachParts Mercedes-Benz Forum

The Warden · #1 08-18-2003, 11:39 PM

Hello!

As I've mentioned before, my engine fan clutch is dead. Unfortunately, my auxiliary fan's dead as well (need to replace the brush housing; the plastic's all melted), so there's nothing except for ambient air coming through the radiator at whatever speed the vehicle's traveling at. For the most part, this actually hasn't proven to be a serious problem, although I had to shut the a/c off while driving up the Grapevine yesterday because the coolant temp had gotten to 100° C.

I haven't found another aux fan assembly yet, and I can't afford to replace the fan clutch, so is there by chance a way to lock the fan manually until I can replace the clutch?

Thanks!

Also, on a similar note, I know that a/c output can be adversely affected at low speeds if the fan's non-operative, but is the a/c output also adversely affected at high speeds? What speed does the fan push air into the a/c condenser and the radiator at?

Maxwell · #2 08-19-2003, 02:41 AM

you could get a bolt on flex fan for like twenty bucks

The Warden · #3 08-19-2003, 02:46 AM

This'll bolt on in place of the fan clutch/fan that's there right now?

Also, how difficult would that be to remove? There's no real reason to have the fan on unless it's a hot day out...

Thanks!

kerry · #4 08-19-2003, 10:05 AM

On some Mercedes fan clutches , there is a flat metal tab that can be bent to fit in a slot which makes the fan operate all the time. I believe it was on the engine side of the fan on the one I looked at. The instructions in the owners manual, stated that once it was bent and the clutch mechanism overcome, the vehicle should not be driven for more than 600miles before repairing the fan clutch. I don't see why it couldn't be driven forever in that condition.
I think (I'm not certain) that I read of this procedure in the manual for my 409d van. I don't know if a similar tab exists in the car model diesels.

The bolt on flex fans are more than $20. More like 60-70.

gsxr · #5 08-19-2003, 11:45 AM

Don't use the bolt-on flex fans. They are generic and mostly for looks, not performance. They usually don't pull much air either. Notice how shallow the blades are compared to the stock fan? Just get a new (or used) fan clutch, they're not THAT expensive! Try Kaleb (striplin@mbz.org), he probably has one for sale cheap.

sixto · #6 08-19-2003, 12:14 PM

Since you're ready to replace your clutch fan, get a can of STP engine treatment and a syringe with no needle and fill your clutch with 15-20ml of syrup. For the price, it's worth testing to see if you can extend its life.

Toyota sells 18ml blottles of silicone fluid in 3 variations of... uhh... whatever centistokes describe. It's about $15 per bottle. Part numbers are in the archives.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

gsxr · #7 08-19-2003, 12:49 PM

I believe the fluid re-fill theory only works on the newer OM60x clutches. Warden has an OM617 - don't know if that applies. BTW, a guy on the MBZ list bought some 12,500 c/s fluid for $40/gallon (!!) from a chemistry supply house. He's going to experiment and let us know how it works. Hope I can buy a pint off him!

#8 08-19-2003, 01:00 PM

I have a extra fan clutch that i bought and did not need from
Potomac, Im not sure if its for your car but it will work on a 300sdl
I will sell it to you for $50 if you are interested
Thanks
Bob

leathermang · #9 08-19-2003, 01:30 PM

"Don't use the bolt-on flex fans. They are generic and mostly for looks, not performance. They usually don't pull much air either. "

Not sure which you are referring to here.... can you be more specific ? Does this apply to the 9 bladers in Performance Catalog , for instance ?

gsxr · #10 08-19-2003, 01:33 PM

Yep - most all "flex" fans, where the blades bend as RPM increases, are a way to cheap out of using a true clutch (IMO). Most of ones I've seen are available in lots of pretty colors, which is the most important attribute of a cooling fan, right? What color it is?

Personally I want the fan that moves the most air! Or at least the proper amount of air. And that generally ends up being the stock fan with a good clutch.

leathermang · #11 08-19-2003, 01:42 PM

The one I saw was from MB and listed as an upgrade.... don't know if it was " flex" or not... did not look like it....

gsxr · #12 08-19-2003, 01:54 PM

Anything from MB won't be a flex fan. The flex fans are aftermarket items with thin metal blades that straighten out as RPM goes up, reducing drag (because it stops pulling air) at high RPM's. They are directly bolted to the drive pulley. I'm almost positive you can't get one to bolt up to an MB easily. At least I hope not. You'd be better off using bailing wire to tie the stock MB fan to the failed clutch, and just try to keep RPM's down (say, under 3500).

Maxwell · #13 08-19-2003, 02:01 PM

You could just bolt a 240D fan on there, or bolt the existing fan without the clutch, if either of those would work, then just take it of in winter like the truckers do. slightly inefficient, but gets the job done, and won't just stop working again like a clutch could. The Clutch is definitely the most efficient when its working, but there's something to be said for the dependability of a bolt on fan.

ercoupe · #14 08-19-2003, 02:29 PM

The Warden:
When you say "my fan clutch is dead" do you mean that the fluid has leaked out or the bi-metal strip is not causing the clutch to engage?
When the clutch on my 123 stopped operating I removed the bi-metal strip on the radiator side of the clutch which then caused it to engage shortly after the engine was running.
If you are carefull when removing the bi-metal strip and don't bend it you should be able to replace it if you want to.
Maynard Smith.

The Warden · #15 08-19-2003, 05:46 PM

I don't know if fluid has leaked out or not. IIRC, it's clean in that area, but who knows how long the car's been driven with the clutch non-op. I also don't know about the spring...I didn't know it was exposed, actually.

The fan does not engage at any speed, although I don't think the fluid has leaked out entirely since I feel resistance when turning the fan by hand...