Cooling Fan Melted -- Why? ('92 Mazda 626)

What do you mean by repeatedly? How long do they last? What do you mean by melted? Are the electronics failing or are the blades melting?

Thanks for the reply. I wrote that early this morning and my brain may not have been in gear.

The fan blades warp and then the fan evenually breaks off of the nut that holds it to the fan motor.

The first time was in May. The second time was slow. First the blades warped so that it was hitting the cowling. I trimmed off some pieces for an interim fix. Then it started hitting again and I loppped off some more. It worked fine for more than a month, then broke off the nut a bit more than a week ago.

Electronics continue to work fine.

So, actually, it's only been twice, but that's about as repeatedly as I can afford. I leave for Oklahoma, from DC, in about a week and a half and am hoping to resolve this.

Hamish =============================================

Could you possibly have a vibration issue... not heat. Could the blades be developing stress cracks from vibration caused by an imbalance or mounting issue? Just a thought...

Professor

Newp. The fan blades, in addition to warping so that they hit the cowling, actually developed bubble-like depressions from the heat.

It is clearly a heat/melting problem. Doesn't seem likely, but there it is.

The crazy thing is, I would think that, whatever would cause this, even if it had somehow escaped my notice, would be known to at least a few people. But no one seems familiar with this problem. If it had only happened once, I would have figured the fan itself was somehow defective, like made out of the wrong grade of plastic, for instance. But it seems unlikely that I got the only two bad fans in the world.

I would appreciate hearing from anyone who has had this problem, and what they have tried, even if they don't have a pat solution.

And I would REALLY appreciate a pat solution.

Hamish ==================================

Hamish,

Wow, there must have been some serious temperature involved.

I'm completely stumped and I suspect others are also. So I thought I'd throw out a few ideas and see if it tickled someone else's thoughts.

Seems unlikely to be air coming in to the front of the car (unless you forgot to tell us you're a stunt driver and regularly drive thru flames) ;-) Even Death Valley only gets up to about 120-130 degrees F.

Also seems unlikely that the heat is coming from the radiator since I would expect it to boil over long before melting the blades.

I cannot imagine the fan motors generating enough heat to melt the blades and still working for any lenght of time.

Only place I can think of that gets hot enough is the exhaust system.

I once had a Datsun pickup where the timing got so far retarded that the exhaust manifold would glow red (it was real scary looking at it).

Perhaps you could use a roasting thermometer to measure the temp when running and when turned off after running. This could give you an idea of the temperatures involved.

Brian

Maybe you lost a heat shield off the exhaust. You could make one as a barrier to the heat in that area using aluminum and bolt it or pop rivet it to something.

Only a guess from a lurker:

I think you may have installed the fan backwards. Usually trhe fan sits at the front of the radiator and pushes the air towards the engine bay. You may have installed the fan with the blade pitch inverted, not only inhibiting the proper airflow, but if the car comes to a standstill for a while and the fan turns on, its sucks the hot air towards it through the rad (so the rad does cool) but sucks the hot air over itself, instead of from outside towards the engine bay and out and under the bay.

You know, exhaust fumes shooting at the fan blade is a thought. That would explain why the temp gauge registers normal while the fan blade melts. Further, I did have a bad manifold gasket that I replaced in between the first and second times this happened. Because it silenced the exhaust noise, I believe that it must have stopped the gas flow too, but I better have a close look at the possibility.

Thanks,

Hamish ============================================

The heat shield is in place, but for reasons noted in another post exhaust heat, in some form, is starting to seem like the most likely culprit.

Hamish ===================================

Nah, I wish.

Actually, even if it was possible to put it on backwards, if you think about it a minute, the blade pitch would be the same with the fan turned around. Assuming that the fan motor turned in the same direction, it would still impel air backwards.

Hamish ==================

Found it. There is a pinhole in the exhaust pipe that blows hot exhaust fumes at the fan.

Thanks to all for input.

Hamish