Cooling Fan Rubbing

snevman · 08-11-2003, 12:17 PM

I have a 1989 Carerra 3.2 with 94,000 miles.

Yesterday I drove for about one hour and parked the car at a store for 20 minutes, no problem. I then drove for about 5 minutes to another store, no problem. I returned to the car about 30 minutes and when I started the car I heard an awful ping, ping, ping.

I shut it down and inspected the engine area and determined the fan blades were hitting the shroud on the bottom.

I took off the fan belt and spun the fan and could hear a slight pinging from the fan blades rubbing on the shroud. When I held the shaft of the fan and pulled up while spinning, there was no rubbing.

I reinstalled the fan belt and started with no pinging, a few minutes later at idle I heard an occasional ping and now nothing. I drove the car the hour back home without incident.

The question, is the bearing in my alternator bad? Is it something else? I am hoping there is an easy explanation.

Please help.

Thanks,

Scott

masraum · 08-11-2003, 12:18 PM

sounds like the alt bearings to me.

Rot 911 · 08-11-2003, 12:51 PM

Or it could be cracks in the fan housing allowing the housing to take on an oval shape. About six months ago I went through the same ordeal and it turned out to be a fan housing with lots of stress cracks. Either way you are going to have to remove the alternator and the housing.

Jim Sims · 08-11-2003, 12:57 PM

Either alternator bearings or cracked fan shroud vanes. I would bet it's the alternator bearings. Address it now before it "takes out" more parts like the fan or leaves you stranded. You cannot run the engine without the fan; well you can run it until it seizes up from overheating. Cheers, Jim

Jack Gresham · Jack Gresham's Garage

I have a similar problem, in my case one of the blades has a spot of inter-granular corrosion causing the blade to grow to the point of just touching the shroud, the corrosion is easy to miss, it looks like a bump with a small crack in the center. Check your fan with a flashlight for corrosion, you can also feel for a bump. In my case I am waiting and watching, since it rubs every now and then and just barely with no real damage to the shroud, one day I will replace the fan.

304065 · 08-11-2003, 02:09 PM

Remove the fan hold-down strap. Remove the belt. Pull out the alternator. Tighten the nuts that hold the alternator to the shroud, but the top ones only. Spin the fan. By torquing the top nuts it should pull the fan back into alignment. Reinstall and enjoy.

Don't tighten them so much that you crack the fan shroud.

88911coupe · 04-15-2024, 04:55 PM

I'm having a similar issue on my '88. The engine is out so I can access the fan but the alternator seems solid...does not seem to have any movement in the shaft. ALSO, I only have 1 blade that is actually rubbing to any degree. The blades immediately before and after are faintly rubbing. Doesn't this point towards the issue being with the blade(s) and not the whole set up? I can see no cracks anywhere in the fan housing and have always been careful to not over tighten the strap bolts. Thanks for any input.

ErrorMargin · ErrorMargin's Garage

It is either the alt bearings or a cracked housing….or both.

You need to remove the housing to really inspect for cracks. And the alt bearing might only be moving under heavy load.

Alan L · Alan L's Garage

The cracks (if any) are likely in the rear at the alternator mounting points. You likely need to remove the alternator to find them. And a decent auto elec shop will be able to tell you if the bearings are in spec if it is not obvious to you.
I am guessing the rubbing is in the bottom of the housing?
Tension from the belt loading a wobbly bearing, or pulling a crack.
Alan

88911coupe · 04-16-2024, 06:15 AM

Thanks, I'll just remove the whole thing as suggested and take a thorough look at the backside. What's odd though is that only 1 blade is rubbing. The two "adjacent" blades are very faintly rubbing which would seem to indicate that the fan itself is somehow warped or out of round. Yes, the rubbing is at the bottom of the housing. I have been careful to not over tighten the strap.

ErrorMargin · ErrorMargin's Garage

Quote:

Originally Posted by 88911coupe

Thanks, I'll just remove the whole thing as suggested and take a thorough look at the backside.

For your reference, I created this thread with sources for new fan housings:

https://forums.pelicanparts.com/porsche-911-technical-forum/1158384-replacement-fan-housings.html

And here is a picture of one of the cracks in my fan. There were two other much smaller cracks that could only be seen in the right light. This is from an 84 Targa.