Strange goings on, then fan belt warning light...

[Guest]

All,

I indulged in the typical Sunday morning "spirited" drive this morning - to dry the brakes out after cleaning the drillings of dust deposits and the subsequent wash. All was well until, at about 6000rpm in 3rd, I heard a sound much like a stone hitting a wheel arch lining, shortly followed by the red exclaimation mark and fan belt warning light. Naturally I brought the car to a stop asap, and headed aft to take a look. The first thing I noticed was a dimple in the paint on the engine lid, clearly caused by a small projectile hitting the inside of the lid at very high speed. My next observation was that both belts to the engine fan appeared intact, and retained good tension. I was surprised to see that three blades of the fan, previously pristine, were damaged on their leading edges, as if flakes of the alloy had been chipped off. I assume it was one of these (tiny) flakes of metal that flew off and damaged the engine lid.

Has anyone heard of a problem like this before? I found myself wondering whether another flake could have caused an impact to the fan belt sensor to trigger the warning. Would the light illuminate otherwise if the belt is not broken? (I assume I am right in thinking that the belt in question is one of the concentrically driven belts attached to the main fan rotor, rather than a hidden belt? If I am correct then I can only guess that a stone must have somehow got into the engine bay and hit the fan when it was at high rpm. Obviously I have booked the car in to be checked out and repaired, but my belief that the belt is not to blame would seem to be supported in that the oil remained at typical temperatures while I coaxed the car back home.

Any experience and thoughts much appreciated as, being a relative newcomer to 993 ownership, my thoughts have inevitably turned to the potential for a substantial wallet-bashing! The car is a pre-varioram C2, having covered 80 thousand miles, and with an excellent service record.

Thanks!

 

[vic cohen]

Very rare in my experience , however last winter had an off in a 993 at Donnington .................suspect i picked up something, subsequent huge bang from engine compartment , all dash lights on, engine still running..............stopped at pits .......in whatever order, the following, u guess!
Actual fan blade torn off at hub , fan belt snapped [suspect cut trough] lower pulley bent and knock sensor [one of the 3 on top] wires severed .................Clear suspicion flying rock ?
Typical Porsche , common sense, borrowed fan belt and drove 80 miles home below 3000 revs

 

[Guest]

Vic, do you recall how much it cost to replace the fan rotor? In terms of the repair I am looking at I can see a trip to the body-shop to have the engine lid damage repaired, presumably a new fan belt and sensor re-set, and possibly a new fan rotor. How big a job is it to change the fan belts? - they are quite prominent, so I am hoping that the belt change is not a major task. I am guessing that fiitting a new fan will be the most expensive part of this unhappy incident if it turns out to be necessary... they look pricey!

 

[vic cohen]

Was unfortunately an RSR ...........wrongly presumed fan rotor ws standard partand wud get from breakers .....WRONG!
Sensor was rewired , 10 mins ..........fan belt not too bad , i only have one ,no aircon ,they are a bit fiddley i usually undo top pulley , 3 nuts ? and realign ;pulley was lower pulley also not tooo bad ...........truly cant remember the actual bill, i use Jaz Motorsport, only painful bit was having to buy new fan /rotor!

 

[LK_991GTS]

It may have been the belt sensor wheel that has broken. This would have caused the dashboard light to come on. Is yours still there?

 

[Guest]

Lawrence,

After speaking to a few folks I am coming to that opinion myself, although I haven't checked the car yet. It seems that the most likely root of the problem is that the sensor switch broke, was slung into the fan by the belt, hit the fan blades and damaged them, before being fired into my engine lid causing damage like an airgun pellet - which will necessitate a trip to the bodyshop. All in all, an unfortunate set of coincidences. If only the flying debris could have hit literally any other part of the inside of the engine lid there would have been no visible damage caused! The good news is that the fan itself will probably not need to be replaced. I suspect that some gentle work with a piece of emery cloth on the blades will suffice.

Thanks for your advice!

 

[LK_991GTS]

If bits of your fan blade are missing, I'd be worried that it would be unbalanced and may thus cause damage perhaps to the bearing(?) later on, particularly given the high speeds involved.

Also, I've just remembered that there was an upgrade to early-type pulleys, with the early types sometimes breaking and the parts flying off and denting the engine lid (sounds similar!) (I may have read this somewhere on p-car.com.)

 

[Guest]

Sound advice, and I will look into the pulley situation. I certainly don't want to see this happen again. Something for others with early 993s to think about too if a cheap upgrade at service time can eliminate the probability.

Needless to say the car will be thoroughly checked out, and anything that needs replacing will be replaced. A whole new fan unit including alternator, housing, and rotor, is around GBP 250 from Porsche-apart, so not the end of the world.