Is my fan toast???

[Leland Pate]

I pulled my fan and shroud tonight to start a polishing project.
Low and behold, there is a small chunk taken out of one of my blades.

Is it dead now?
I know it coould lead to premature alt. failure and all... I was just wondering if this size chunk is catostrophic.


Bummer...

[sliminbay]

I had worse and never seem to be any problem. Just annoying because I knew it was there.

[rcwaldo]

Just deburr the edges of the broken part.. Unless there are migrating cracks, should be fine...

[Al S]

I would just make a nice semi-circle out of it with a dremel, then make another one on the opposite side to match.

[Zeke]

Originally posted by Al S
I would just make a nice semi-circle out of it with a dremel, then make another one on the opposite side to match.

That would be a perfect solution if you knew it was then balanced. I would send it to a balancer and let him take the next bite out. He might take 2 smaller bites at angles rather than one. Harmonics.

[UTKarmann_Ghia]

Here's a silly question (that I just cant stop myself from asking): If you had the chip that came out, could you jbweld it back in place? If for nothing else, maybe just for looks.

[304065]

Leland, it's just like a prop on an airplane. The crack as it is now creates a "stress raiser" that will lead to separation of the entire blade eventually. You can take a file and carefully make the crack into a nice semicircular shape, this will distribute the stress and make it less prone to cracking. However, by doing that you've changed the weight of that blade, which creates a balance problem.

Given the relative cheapness of fans and the important function they plan, I say replace it.

[JonT]

That seems very odd--what would cause that? Hope replacements aren't expensive--could prolly pick up a used one for a decent price.

[Drago]

That will fail, eventually. What's a used fan go for these days?

[Rick Lee]

Leland, drop Dr. Timmins a line. He has a mountain of fan/alt. assemblies in his garage and will probably treat you right on price.

[si2t3m]

When i bought my 3.0L one of the fan blades look like this. Lucky, I was able to find the chip under the engine shroud. I brought it to a local welder that knows how to weld magnesium and got the chip welded back in place.

Marc-Andre

[john walker's workshop]

i have yet to see an entire blade come off because of a notch like that.

[Rot 911]

Originally posted by john walker's workshop
i have yet to see an entire blade come off because of a notch like that.

I agree. Keep in mind that one blade probably only weighs less than 20 grams? That piece missing probably weighs less than 5 grams. I've seen lots of fans with more missing pieces than that running for years without replacement.

[JonT]

The more I think about it Leland you may be on to some new adventure in weight loss savings. Try cutting off all the blades cept for 2 or 3.

[Kurt B]

Feather in some JB weld chief! Someone post what a used fan does go for these days, I'm curious. That's one of those things where you don't even want to know what Porsche will charge for one!

[Rick Lee]

I think you can get a decent one for under $200. As long as you're in there, this is a good time to get the fan and housing powder coated.

[TerryBPP]

There is one in the Pelican classifieds for $80 bucks right now.

[Hetmann]

Deburr the chip and rebalance your fan. This has been discussed here before. Briefly, you can build a little jig with two parallel horizontal edges (sheet metal is best) and suspend you fan on a dowel (piece of PVC). Spin your fan. Heavy part will drift to bottom. Remove material from the detents on the inside. Repeat until fan is balance.

[ruf-porsche]

Originally posted by TerryBPP
There is one in the Pelican classifieds for $80 bucks right now.

We already have a deal on the $80.00 fan.

[earossi]

The mass of the fan and the speed at which it turns should not require much, if any rebalancing. As posted previously, you need to remove any stress risers by "rounding out" the edges around the break. You'll want to examine the area around the break to be sure there are no small cracks which would then propegate into the remaining blade. If you find cracks, grind them out.

On the issue of balance, I doubt that your fan would even notice the small piece that is missing. If you are really concerned, you could just "duplicate" the size and location of the chip, but at 180 degrees from the original crack. This will put the fan in a good static balance. The cost of a dynamic balance is prohibitive and would force the decision to just replace the fan. Keep in mind that the fan does not turn over that fast.

Bottom line, clean up the area around the crack and give the fan a trial run. My guess is that you'll never be able to measure any unbalance nor any loss in cooling efficiiency.