I recently upgraded from an e36 to an e92 328i and put the e36 up for sale. Just 10 minutes before the potential buyers showed up from about 4 hours away, the e36 shed the radiator fan blades in a spectacular fashion on the way to the meet spot. I recognized the noise and killed the engine right away and coasted to a safe place. Upon opening the hood, I noticed that the fan clutch was way misaligned and whatever blades held on, were a few mm from contacting the upper radiator hose and the radiator mesh. At this point it was clear that the water pump shaft had come loose for one reason or another. Needless to say another few seconds of running the engine could have easily shredded the radiator and some hoses. Luck was on my side.
In a way I'm glad that the water pump took a sh!t on the way to the meet spot and not during a test drive or if the guys had bought it, on their way back.
Fast forward a week or so and I finally found some time to dig in, and pick apart the cooling system to see what the damage was. Sure enough, the fan clutch wobbled like a newborn's head but I didn't see any punctures or leaks from the flying blades. I sighed in relief and went to take it out.
Taking out the water pump is normally a tedious, but not a tough job. Not with my car... The infamous fan clutch nut was seized to the water pump shaft with military grade rust and no amount of penetrating oil or leverage would brake it loose. The thing is, the fan clutch is usually the first to come out and all else follows in a systematic, and simple fashion with plenty of clearance to reach bolts and nuts. With that ability gone due to a clingy fan clutch, my options became quite limited and I had to more or less figure things out on the fly.
The solution presented itself when I leaned on the radiator and nudged it a cm or so. I decided then to take out the radiator and the shroud to give myself enough space to reach about the fan clutch. The radiator, the shroud, and the air box all were extracted. This gave me enough space to take out the water pump and the fan clutch as a single unit. Some details aside but I'll tell you that it's a b!tch of a method because of the low clearance between the water pump pulley and the water pump bolts. But it all came out in the end but not before puking whatever coolant was left in the block all over the ground.
Fast forward a few hours and I managed to take off the fan clutch from the water pump shaft on a work bench using some unorthodox methods. But in the process I got a chance to pick apart the water pump and find out the cause of all of this mess.
As it turns out, like the previous owner had told me, the water pump was replaced with an upgraded unit that has a metal impeller. What I found out though, is that he likely got the cheapest possible upgraded water pump which used a plastic bearing body to hold the shaft in place. This plastic body shredded itself and loosened the shaft. So a common failure (overheating due to a degraded plastic impeller) was replaced by a less common but a more dramatic one.
I have all of the new bits aligned and mentally preparing myself to put it all back together now.
The moral here is: When you buy upgraded replacement parts, don't cheap out and do proper research. Otherwise stick to OEM...
You can see the busted fan blades and the pump the fan clutch is attached to by the mess from the coolant puking out of the water pump throat. The radiator and the shroud are along the left edge and the air box is near my tool case.
Upgraded water pump was a cheap POS.