Thanks Jay, I ordered the bolt from Merc so hopefully it will be the right one!
3 Allisons, All Down
- Thread starter 2fast4mom
- Start date
JaySmithRacing
Active Member
Would'nt hurt to up grade from the OEM part Lou.. After all that OEM one failed !
Jay
Jay
Good point! But I guess I don't know for sure if it had the OEM bolt in there in the first place?
hack02
Well-Known Member
I wonder why the oem bolt broke in the first place. Alt. trying to seeze up, idler trying to do the same. Flywheel loose causing vibration to loosen ecu bolts? Or just fatigue failure of the idler bolt. Get with it Detective Lou, inquiring minds want to know.
I am right with you, Steve. Things don't happen for no reason.
At first I thought the alternator was trying to seize up because when I pulled off the cowl, the alternator was too hot to touch. However, after I got the flywheel cover and the belt off, the alternator had cooled and it was able to be spun easily by hand, with no roughness or noises. Same goes for the idler wheel.
Therefore I came to the conclusion that the alternator was hot owing to the continuous belt slippage against its pulley. Jury still out on that theory, and will be until I get it running again.
There could be some kind of harmonic vibration at a certain rpm that caused the bolt to snap and the ecu screws to back out. How to diagnose this, I don't know.
Unlikely the idler bolt could have loosened; the remains of it are still in place with red locktite.
Hopefully it was a case of metal fatigue in the bolt. And others have told me that those ecu screws don't stay put on the 280's no matter what you do! :?: :?: :?:
At first I thought the alternator was trying to seize up because when I pulled off the cowl, the alternator was too hot to touch. However, after I got the flywheel cover and the belt off, the alternator had cooled and it was able to be spun easily by hand, with no roughness or noises. Same goes for the idler wheel.
Therefore I came to the conclusion that the alternator was hot owing to the continuous belt slippage against its pulley. Jury still out on that theory, and will be until I get it running again.
There could be some kind of harmonic vibration at a certain rpm that caused the bolt to snap and the ecu screws to back out. How to diagnose this, I don't know.
Unlikely the idler bolt could have loosened; the remains of it are still in place with red locktite.
Hopefully it was a case of metal fatigue in the bolt. And others have told me that those ecu screws don't stay put on the 280's no matter what you do! :?: :?: :?:
Hey Lou
Lou, remember me? We emailed when you first found this site. I haven't been here in a long time and man-o-man, things have changed!!
With respect to your alternator problem, my first suspicion would be TOO much belt tension. It would heat up the alternator bearings causing them to bind. Then, it would be a self-perpetuating cycle that could fatigue the idler and mounting bolts and explain the rest of things you describe.
I've never really studied the 280 alternator system, but that would be my first guess after reading your description. Does the 280 use a flat, "V", or syncronous (toothed flat) belt? Is the tensioner spring-loaded or fixed position? If it's spring loaded, was there spring travel left when the belt was at tension?
Does the alternator shaft turn freely without the belt?
Food for thought.....
Chris
Lou, remember me? We emailed when you first found this site. I haven't been here in a long time and man-o-man, things have changed!!
With respect to your alternator problem, my first suspicion would be TOO much belt tension. It would heat up the alternator bearings causing them to bind. Then, it would be a self-perpetuating cycle that could fatigue the idler and mounting bolts and explain the rest of things you describe.
I've never really studied the 280 alternator system, but that would be my first guess after reading your description. Does the 280 use a flat, "V", or syncronous (toothed flat) belt? Is the tensioner spring-loaded or fixed position? If it's spring loaded, was there spring travel left when the belt was at tension?
Does the alternator shaft turn freely without the belt?
Food for thought.....
Chris
HEY CHRIS!!! Yes, I remember you...long time no see; good to have you back! 
The belt is a flat, grooved one and the pulleys have grooves that match. The old belt is showing signs of wear at its edges (frayed areas) so I ordered a new one. $18 not too bad.
The tensioner is fixed (no spring tension). The manual says to have 1/2" of belt flex between the tensioner and flywheel pulleys. I've always found this type of spec to be rather arbitrary. The manual also says to apply 70-80 lbs if using a "strain gauge belt tensioner".
Yes, the alternator now turns freely and smoothly without a belt attached. It just makes a slight sort of hissing sound when you spin it - probably normal?
The belt is a flat, grooved one and the pulleys have grooves that match. The old belt is showing signs of wear at its edges (frayed areas) so I ordered a new one. $18 not too bad.
The tensioner is fixed (no spring tension). The manual says to have 1/2" of belt flex between the tensioner and flywheel pulleys. I've always found this type of spec to be rather arbitrary. The manual also says to apply 70-80 lbs if using a "strain gauge belt tensioner".
Yes, the alternator now turns freely and smoothly without a belt attached. It just makes a slight sort of hissing sound when you spin it - probably normal?
GFinch
Well-Known Member
What kind of noise would you make if someone grabbed you and spun you! :shock:
Probably just the brushes on the slip rings.
Altenators make a lot of heat when producing electricity. Also when over charging(volt regulator) or diode bridge bad, bad battery or connections. A battery that is shorted intermintintly will knock out anything electronic, the altenator has to see the batterys voltage or it can spike a couple hundred volts into the system!
Gary
Probably just the brushes on the slip rings.
Altenators make a lot of heat when producing electricity. Also when over charging(volt regulator) or diode bridge bad, bad battery or connections. A battery that is shorted intermintintly will knock out anything electronic, the altenator has to see the batterys voltage or it can spike a couple hundred volts into the system!
Gary