New alternator bearings failed only one year after installation

[martidj]

The other day I backed my 911SC out of the garage parked it and turned off the engine. After a couple hours I started my 911SC to return it to the garage when I hear grinding noise coming from the cooling fan. Immediately I turned off the engine to investigate, opened the engine compartment lid and turned the cooling fan by hand. I could feel the fan rubbing the fan housing. How could this be? I just installed this brand new Valeo alternator a year ago. Did I have the fan belt to tight? I used five shims between the pulley halves and one behind the washer, this gave me about 5 mm of belt deflection which is recommended by the Bentley repair manual. Is the Bentley repair manual incorrect? Should I have used all six shims between the pulley halves?

[pete3799]

Did you actually take the belt off and spin it?

[john walker's workshop]

Possible cracked fan housing. Happens a lot. Try it with the belt a tad looser for now.

[martidj]

Thanks for the reply John, I noticed a crack in the housing when I replaced the alternator, wasn't a problem at that time. I will remove the alternator and see what I find.

[impactbumper]

worse case, the Valeo unit should have warranty also.

[86 911 Targa]

Originally Posted by martidj

The other day I backed my 911SC out of the garage parked it and turned off the engine. After a couple hours I started my 911SC to return it to the garage when I hear grinding noise coming from the cooling fan. Immediately I turned off the engine to investigate, opened the engine compartment lid and turned the cooling fan by hand. I could feel the fan rubbing the fan housing. How could this be? I just installed this brand new Valeo alternator a year ago. Did I have the fan belt to tight? I used five shims between the pulley halves and one behind the washer, this gave me about 5 mm of belt deflection which is recommended by the Bentley repair manual. Is the Bentley repair manual incorrect? Should I have used all six shims between the pulley halves?

Did you install the woodruff key correctly?

FYI, I used three shims on each side for our M/Y 86.

pm me as needed.

Best,

Gerry

[zedsn]

I tend to leave my belt a tad loose because it does tighten up the hotter it gets.

[martidj]

pete3799,

I should have said I removed the belt. I'm glad this happened at home.

[Bill Douglas]

I have my belt a lot more loose than that. It doesn't seem to slip or flap around.

[RAW911]

+1 on what John says!
Check the struts on the alternator shroud for cracks. Your bearings may be OK.





Replacement aluminum shrouds are available from our host. R&R is an easy project.

[911obgyn]

When I took my alternator in to get it rebuilt the guy at the shop said he was having problems getting anything other than chinese bearings, I have had mine in for 2 years now and run my belt just a tad loose and use the Porsche belt, it fits best.

[911obgyn]

When My bearing went it sounded like I was being followed by a jet plane.

[martidj]

You are right Gerry, the Woodruff key was not installed correctly by me. I was lucky this happened at home. This could have been a very expensive repair.