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Fan Blade Failure, and a Fix

December 3, 2010 | Troubleshooting & Repair
Text and photos by Jim Ansite and
Roy Lock



You are enjoying a drive on a lovely fall day. Cruising along at 3400 RPM’s, suddenly there is a loud bang! You quickly shut off the engine and coast off the highway. Getting out of the car for a closer examination, you see a big puddle of oil, a smoking engine, and realize that shutting off the engine was a wise decision.

Previously, you had noticed a whistling noise at speed and had tried to have it diagnosed and fixed to no avail.

Once you get your 356 up on the lift, shards of metal fall out of the engine compartment. A close examination of the shrapnel indicates a cooling fan failure. As dangerous as those are, all the shrapnel was contained by the engine and its components. It was truly a catastrophic failure. ALL the blades separated from the two cooling fan end plates.

Never in my 35 plus years of association with 356’s and 912’s had I seen all the blades separate. Here is the evidence of failure.

Here are the pieces of the cooling fan that we could find. Incredibly, the only damage was contained and confined to the engine. There was no damage to the body or other components in the engine compartment. If it had severed a fuel line the result could have been disastrous for the entire car.

A close examination of the engine disclosed fan blades embedded into the right hand bank of cylinders. What force was exerted to cut through the metal and then lodge onto the cylinders? Other separated blades cut into the fins on the cylinder head.

Luckily, the case did not suffer any damage. However, the oil cooler was not so lucky. Two blades found their way to that component and damaged the cooler beyond repair. So much for the new oil cooler from the recent engine rebuild.


Inspection of the fan shroud area showed the path of the separated cooling fan blades. The fan blades were still encased in the fan shroud, embedded in the oil cooler, the right hand bank of cylinder barrels, and cylinder head.


The fan shroud itself fared no better. It suffered internal baffle damage from fan blades that separated inside the shroud and did not exit onto the engine. That damage was contained within the fan shroud. But it bent the sheet metal of the shroud.

As bad as this failure appears, it is an easily repaired. A new oil cooler, replacement cooling fan, and a fan shroud. Relatively easy components to procure. Once dressed, fin damage to the cylinder head and cylinder barrel were within acceptable limits.

Now comes the lessons learned. The owner had a spare cooling fan. He brought it over for his mechanic to install. Having learned the previous lesson, he closely examined this cooling fan. Guess what? Yep, another failure waiting to happen! This one had bent blades all the way around and they were loose.

The blades should be straight in the cage. Notice how they appear curved? Those blades were starting to rattle around and would have failed.

The mechanic told me that when he rebuilds an engine, he fuses the blades to the cage. Here is an example of a “fixed” cooling fan. He alternates upper and lower stake and then does the opposite on the other side.

So next time  your engine is out of the car, perform a quick simple inspection of that cooling fan. If you do, it will give you peace of mind whenever you are driving your 356.

2 Comments

Profile missing thumb
Bruce Herrington
March 18, 2013 at 3:11 AM
Der Maestro said that if you take care of your Porsche it will take care of you. I feel honored that when the fan let go on my '68 912 as I coasted to the left turn into my development, the pieces all stayed within the fanhousing, and I had enough momentum to make it around three corners and into my driveway.<br /><br />But at a VARA race an acquaintance's fan let go at high RPM. The blades went through everything, including the engine lid!
Profile missing thumb
Bruce Herrington
March 18, 2013 at 3:11 AM
Der Maestro said that if you take care of your Porsche it will take care of you. I feel honored that when the fan let go on my '68 912 as I coasted to the left turn into my development, the pieces all stayed within the fanhousing, and I had enough momentum to make it around three corners and into my driveway.<br /><br />But at a VARA race an acquaintance's fan let go at high RPM. The blades went through everything, including the engine lid!