Fan Clutch Change - PeachParts Mercedes-Benz Forum

BillGrissom · #1 11-23-2013, 12:21 AM

I had a sheet-metal sound coming from the front of the engine in my 85 300D. Thought it might be the fan clutch (nylon fan) since felt like it rotated a bit too easy. I cleaned and painted another I had (81 engine w/ alum fan), only to find a chunk missing around the seal (photo). Bummer since that one was an original and still very tight.

I bought a new clutch for $38 w/ free shipping, much cheaper than alternates. I took a chance since the title didn't list any 300's and the table listed only 300SD and only to 84 (last alum fan?). I understand the 300D engine is the same, though some engine bay parts do vary from the 300SD. Anyway, it fit my fan perfectly, so "should work". PN 10957836, with no manufacturer listed anywhere. Probably from the night shift at a Chinese factory that may make name brands in the day. I also read that a nylon fan requires a different fan clutch than aluminum fans. The only apparent difference is that bolts are shorter for the nylon one, since a thinner sheet-metal attachment. Maybe I'll realize a problem in a few years.

BTW, the noise turned out to be the alternator fan blades striking the adjustment bracket (dumb design, but easy fix).

For kicks, I took a stab fitting a Mopar small-block fan and clutch I had (TorqFlo 922747). The clutch fits the water pump perfectly, using the filler sleeve that came in the box, but the Mopar fan is too thick and hits the water pump inlet and power steering crank pulley. Anyway, it proves that most water pumps have the same bolt pattern, so you could likely find a similar thin fan from a Euro car (Volvo, etc) that would fit if M-B parts get too rare. I know some here prefer paying >$400 for a true M-B PN clutch and that doesn't bother me. I just think of it like an IQ test.

BenzTurbo · #2 11-24-2013, 07:11 AM

The w126 gasser fan and clutches fit the om617 and clear everything if you want a cooling upgrade for hot climates but may take a toll on mileage. It's hot here in texas so the roaring fan doesn't bother me with cold a/c in my face when its 110 outside and my temp gauge is at 80!

t walgamuth · #3 11-24-2013, 09:05 AM

I have some fans with no clutch lying about if anyone needs one....both plastic and metal IIRC.

Zacharias · #4 11-24-2013, 06:44 PM

The only catch to interchanging the fan clutch is that you can only use the heavier w126 unit with the metal fan, not the lighter w123 plastic fan. So if you put a w126 unit onto a w123 (which I have done) the fan has to be swapped with it.

Whunter brought this up in a thread a couple of months ago. The heavier fan clutch can cause the plastic fan to come apart, potentially planting a vane in the radiator.

There is a very evident size (thickness) and weight discrepancy between the two fan clutches, having had both in hand at the same time to check. This difference isn't so evident when they are in place with the fan.

Keep us updated on how long the fan clutch lasts. When I was shopping I faced the same price choice/dilemma, until a friend dug up a lightly used new w126 one from a car he had parted out.

cooljjay · #5 11-24-2013, 09:36 PM

FYI on the dual alternator belt system.....you must make sure both belts are identical.....I heard something about the size belts are hard to locate.....confirm you have the correct belts...

BillGrissom · #6 11-25-2013, 12:11 AM

My alternator belts are matched. As the photo shows, Goodyear Gatorback 15411. Not random, they were listed for my car (not PeachParts). I recall I have the 'official' Continental PN's on my 84 300D. Anyway, the sound was from the alternator's fan blade tips striking its bracket. Easy to tell once I spun the alternator by hand. I thought I got rid of it, but now hear it slightly at a certain rpm. This was a PickNPull engine, and tipped over on my stand, so the bracket could have been bent. BTW, the bent tach pin on my damper is another post (Sanden bracket install).

I haven't noticed the new fan clutch "engage" yet, probably because hard to get the radiator hot enough this time of year. Haven't been driving it, just running the motor while fixing it up for my son. Today, I installed Evans "waterless coolant", which was shown recently on Wheeler Dealers and a Jay Leno youtube. It was a pain flushing all old coolant, citric acid flush, and getting all water out. Wish I had done that while the engine was on the stand last February. If it works, I may never have to change coolant again nor worry about corroding the very expensive heater core or radiator.

Pants · #7 10-29-2014, 09:46 PM

I'm fairly new to M-B and had my 83 300SD for just a year before rear-ending an unfortunate Hyundai last night. Damage would have been a lot less had my target's bumper not been shaped as if to slip up over mine when I hit it, thus taking out my grille, condenser, radiator, a bunch of other expected-damaged-parts, and breaking a plastic fan-blade off before we rebounded.

I'm going to start with basic replacements to get me back on the road ASAP: radiator and fan. I have a radiator on order already, but the fan has me in need of your model-change expertise and general swapping suggestions.

It sure looks like a clutch, but if it is, it's totally frozen - something I'd not noticed previously. It's locked up such that I can squeak the pulley around in either direction (with effort) by hauling on the remaining plastic fan-blades (pulley isn't bent, either).

Anyway, whether that was a clutch or not, for this steamy tropical climate, what's the best option for replacement?

vstech · #8 10-29-2014, 09:55 PM

The 83 and up SD had the best available fan/pulley/clutch arrangement. Find parts from an 83 or newer SD and you're golden

Pants · #9 10-29-2014, 10:16 PM

Oresome...as they don't say here. I'll head directly to Pelican, etc...

Thanks - Dave

Pants · #10 10-29-2014, 11:41 PM

I just decided to pull the fan/clutch assembly out to see it better, and began to wonder if my assumption that it's supposed to "slip" almost completely at cold/idle was correct. Like I said, it's locked up tight enough to turn the engine over, even when it's at ambient temp. So...bad clutch, right?

t walgamuth · #11 10-30-2014, 03:50 AM

Right.

BillGrissom · #12 10-31-2014, 03:52 PM

The cheap TorqFlo 922747 fan clutch has been working fine and made it thru our severe summer. It is listed for a 300SD only. People here said you aren't supposed to bolt my 300D fan to it. I did that before I read such. However, I don't follow the concern. I would think the nylon fan is stronger than a cast aluminum fan. I also can't envision these much higher forces from a 300SD clutch.

Pants,
For sure your clutch is bad if you can't spin the fan by hand easily. In theory, it should spin easily when cold and give resistance when hot, but I have never been able to notice much resistance in any clutch fan w/ engine off, either M-B or my old Mopars. Wheeler Dealers had an episode where Ed China shows a bad clutch fan by grabbing it with a gloved hand while the engine is idling. He says he couldn't have held on unless the clutch was bad. I can think of safer tests. I would judge it more by how much air it moves at idle when the engine is hot. Some say it should make a lot of sound, but mine don't and the engines never overheat.

Pants · #13 10-31-2014, 04:27 PM

Quote:

Originally Posted by BillGrissom

... an episode where Ed China shows a bad clutch fan by grabbing it with a gloved hand while the engine is idling. He says he couldn't have held on unless the clutch was bad. I can think of safer tests. I would judge it more by how much air it moves at idle when the engine is hot. Some say it should make a lot of sound, but mine don't and the engines never overheat.

Ha! I cut my hands up enough just doing normal wrenching...I'll stick to checking the fan-clutch using my tongue only. Actually, in my case, I 'checked it' by means of briefly squishing my radiator against it at 5mph to begin with. If the clutch had been working, maybe it wouldn't have holesawed quite so far into the radiator during that moment - and the missing chunks of nylon fan-blade are out there, wondering if they'd still be a unit if only the clutch had been working, now that I think about it.

I never had anything remotely resembling overheating; gauge never left the hard-to-read zone slightly above...what is the first tick? 60C? So I sure hope the new setup doesn't bring new problems.

In this case, I found the price differential between URO's version of the clutch and the next one up to be objectionable (like...2.5x costlier IIRC), and hey, my OEM version had locked up solid, so...how much worse can I do with the URO?

uberwasser · #14 10-31-2014, 05:06 PM

I would have gone with a good working used one before buying URO.

Anything URO that is important to the function of your vehicle is a bad idea. Especially anything that rotates at high speed, I'd wager.

That said, hopefully it works out.