Own a E320?? Check your Fan Pulley Bearing!!
 

Just experienced a disaster with my E320 and thought I would share the story with everyone. Hopefully, it might help someone avoid a costly repair. My E320 has 149,000 miles, most of which are highway miles. It's well maintained--has the engine wiring harness update, the new design head gasket, and the belt tensioner has been replaced a couple of times.

So what happened on my trip?? Well, the bearing that supports the fan pulley and fan clutch literally fell apart at highway speed. The shocking thing was it made very little noise--in fact I didn't know anything was wrong until I slowed down to exit the highway and then heard a god awful clattering. When I popped the hood, there were strange flecks of what looked like metal fragments all over the top of the engine. I started the engine and could see the fan blade was wobbling and hitting some other parts. The pulley was in place, but I could see it was badly damaged and wobbling. The belt survived but was severely frayed.

Called AAA and they towed it 80 miles to Fairfax, Va. to an independent Mercedes repair facility that I formerly used when I lived up that way. Luckily they were open on Saturday. Turned out the metal flecks were pieces of the bearing that were thrown out by the fan blade. The whole assembly was shot--bearing bracket; fan pulley; fan clutch; fan blade; and belt. Strangely, the belt tensioner was fine. Of course, the parts had to come from the dealer and they were closed for the weekend. Two days later, it was back together and purring nicely. The bill was $748.--the parts alone were $481. Add in the hotel bills, and well, you get the idea--quite a Thanksgiving trip.

The repair facility said they had done two similar jobs on E320's this year. Both times the assembly came off completely and damaged the radiator (add another $350 or so). My advice to everyone who owns an E320 with over 120,000 miles--get this bearing replaced before it gets you. I just wish I had known this part was a failure point.

Thanks for the tip! Can the bearing itself be replaced, or is it part of the whole bracket assy? What was the price of the parts you would have had to change if you had done this as preventative maintenance rather than post-failure?

Thanks.

Dennis_300E: I retrieved the old parts and the bracket is a fairly substantial metal piece (about 8" by 4"). The MB number stamped on the part is 104 205 0405. It has a bearing hole about the size of a silver dollar--there is nothing left of the bearing except the race. It does look as though the bearing could be replaced--but not sure if you can buy just the bearing. My bill shows that I was charged for a "Fan clutch bearing bracket, #104 200 1328 with a price of $165. Thus, in the worst case of preventive maintenance, you could change the entire bracket with the bearing already pressed in it. It may even be available aftermarket for less. Good luck. jcd

Same thing happened to me over the holiday with my '86 300E. I did not know these could fail so suddenly. Made a huge racket. The car was towed 205 miles to Salt Lake. The bearing(with bracket) and fan pulley were replaced. Fan clutch was ok. Total cost was $350. It was an independent shop, I am sure they used aftermarket parts.

I guess I can't be too upset. The first thing that went through my mind when the bearing failed was "My timing chain just broke!". :eek:

All fixed and running smooth.



Blake
'86 300E
246,000 miles

I have 112,xxx miles on the E320 and have replaced everything that is driven by the serpentine belt on the front of the engine except the air pump (air pump pulley with bearing was replaced), the power steering pump and the air conditioning compressor. I do not think it would be worthwhile to just try to replace the bearing on the fan bracket. I will see if I still have the old one and maybe dissect it to see if the bearing replacement is possible. I replaced the radiator at the same time as the water pump. The water pump and alternator failed was the reason they were replaced.
I plan on changing the water pump and radiator on the Honda between 100k and 110k.

Yikes!

After doing a search, it looks like I'm on borrowed time with my 300E. At 165,000 miles the fan pulley bearing / bracket is still original. I'm going to change it as preventative maintenance. $108 here at Fastlane. It looks like another tip to go along with this is to purchase the o-ring for the coolant pipe that goes into the thermostat housing, since that has to be removed to get to one of the bracket bolts.

Thanks again!

Fan clutch bearing
 

Greetings All,

I am assuming that the original poster means that his fan clutch bearing went out on him. These bearings are pressed in the clutch housing and in most cases the early warning signs of the bearing going kapoot is the outer bearing shield seperates from the bearing and is visable when looking at the point where the shaft goes into the clutch assembly. I believe the clutch comes as an assembly, but perhaps the bearing can be purchased seperately and pressed in by a shop. If you have high mileage on your vehicle, say 140,000 plus miles, I'd also be pulling up on the water pump pulley to see if there is play, next worst thing to happen on a trip, overheated engine and possibly locked up at that.

Charles

This is a common failure (and it is NOT the fan clutch). Every M103 and M104 I have owned has developed this problem after 100K. In fact, all the components with anti-friction bearings (i.e. ball bearings) should be thoroughly checked at 100K. That means idler pulley bearings, tensioner pulley bearings, alternator bearings, fan support bracket bearings. The only unit that is feasible to renew the bearings on is the alternator, and the Valeo alternators make that virtually impossible. I put a stethoscope on each unit at each service and listen for signs of roughness or noise. I am not sure why this occurs. My theory is that the belt tensioner rubber bush hardens over time and doesn't flex as it should, and vibration and stress is transferred to the various bearings. The water pump, P/S pump don't seem to be a problem.

Thanks for the additional info Vince. I took a look at mine last night, but it isn't really possible to inspect the fan clutch pulley bearing well without taking off the fan and the serpentine belt, which I'll do this weekend.

Can you please elaborate on why the fan support bracket bearing cannot be replaced? It would sure seem more economical and environmentaly friendly to press in a new bearing than to trash the whole thing. There must be a good reason. Can you shed some light?

Thanks.

Dennis_300E. The bearing is not a simple ball bearing. If I remember correctly the inner race is the actual shaft. I had one that self destructed a number of years ago, and that is the way I remember it. I use a stethoscope or a long screwdriver held to my ear to listen to the bearing. Pulling the belt and spinning the various pulleys is another way, though it does take more time.

This thread is best relationship to what I think is my problem on a 91 350SDL ... what do you guys think?

Started getting some extra noise on start up and at low RPMs .... troubleshot to hold fan (engine off) and moving it - I noticed some flexing between what I think is the fan blade assembly and the viscous clutch shaft ... is this where you think your's all blew up?

Would appreciate any input on this - I think this is the issue, but not certain - would like some idea prior to pulling radiator, etc.

Thanks!

George - it is the bearing/pulley assembly that the fan blade attaches to that needs replacing. It is a pretty straight forward replacement if you are a diy'er. I would recommend going ahead and taking care of it if you can see the wobble.
good luck

engatwork,

The bearing/pulley assembly is actually the viscous coupler, right? I can't see any other part in the diagrams .... so, I need to get viscous coupler on order as well as new pump?

I'd have to look. I know that the E320 has the fan bearing built into the pulley bracket and viscous clutch bolts on. The 300D gets this bearing new when you replace the water pump. Once you replace the water pump you just re-install the viscous clutch assy.

any one changed the fan clucth bearing 91 lS400? Same prossess as changing waterpump?