fan belt deflection

78silversc · 04-25-2006, 07:38 AM

Thanks to Wayne's book and this board, I've removed my alternator. had it rebuilt (thank you to Stophos for the recommendation of a re-build shop) and re-installed it.

I have a question about the fan belt deflection. Wayne's book suggests that, if the belt is adjusted correctly, there should be about 1/4" to 1/2" of deflection when pushing on the belt with your fingers , my question may seem dumb but, how hard should you have to push to get that defelction? My belt seems nice and tight and I can get the 1/4" to 1/2" if I press on it pretty hard. So how do I tell if I am too tight?

Thanks
LarryS

Hendog · Hendog's Garage

When doing a valve adjustment you have to turn your motor. You do this by turning the fan with the 24mm wrench (in your tool kit) which turns the motor via the belt. If your belt is to loose, you won't turn your motor past a cylinder's compression point. It's really quite a simple test (tranny NOT in gear).

78silversc · 04-25-2006, 08:30 AM

Hendog: I am really more concerned that the belt is too tight, not too loose. I would guess that if it was to tight it might still turn the motor beyond the compression point no?

Hendog · Hendog's Garage

I see your point. I don't have the answer to that one other than check other belts on other well running cars and see how they feel. You don't want it tight as a guitar string!

Rot 911 · 04-25-2006, 08:35 AM

Sounds like you have it adjusted just right.

78silversc · 04-25-2006, 10:09 AM

great... thanks Kurt.

DW SD · 04-25-2006, 11:06 AM

Clearly you already have this concept down, but maybe for someone finding this thead in the archives: you want it tight so it won't slip, but loose enough that it doesn't load the bearings adding to their premature wear. If you see the pulley deflecting that is a sign of it being too tight OR if you can get the belt to deflect with some reasonable effort.

Doug

David E. Clark · 04-25-2006, 11:25 AM

Quote:

Originally posted by 78silversc
... My belt seems nice and tight and I can get the 1/4" to 1/2" if I press on it pretty hard ...

I realize this is not an exact science but in my opinion, if you have to "press on it pretty hard" to get 1/4" - 1/2" deflection you have the belt to tight. Too tight is really bad for the alternator bearings. The trick is to get it tight enough so that it doesn't slip but not so tight as to overload the bearings. Probably not much help but that's my .02.