Harmonic Balancer options

[boonies]

I am not happy with the engine idle, and have observed run-out (not yet measured) of the harmonic balancer. When I disassembled the engine it was without the center nut & washer (#5 & 6 in the diagram below). I doubt that the hub (#7 in the diagram below) is damaged.

There are a two options for used dampers near me, one is stated to be from a 1969-1981 M30, the other from a 1984 e24/633. The part numbers do not cross over. Any perspective on the interchangeability of m30 harmonic balancers?

 

[2000CS]

What crank and crank hub are you using? There were two different bolt patterns. Early one only allowed one damper position; later symmetric used a locating nub. Belt drive pulley also should match.

 

[Ohmess]

Are you sure the crank nut is properly torqued? And if so, are the nuts holding the balancer to the hub properly torqued?

 

[boonies]

The center hub is original to the '72 M30 and it is torqued above the reading of the torque wrench which is ~275 ft. lbs. The pulley is a later two belt model, but bolt patterns matched up.

I will re-check the torque on the pulley bolts, I believe those were torqued to a general M8 specification ( from memory about 17 ft.lbs).

 

[Stevehose]

make sure the pulley is perfectly flush with the hub

 

[boonies]

Interesting, it is the hub. I pulled the radiator and fan to get access to the balancer.

First checked the bolts and all were torqued as I remember. Then removed the bolts and pulled off the balancer and spun the engine with a remote start button and confirmed it is the hub.

 

[boonies]

I identified the hub as the problem by using a remote starter button while underneath the car. I first checked the assembly while intact and of course the balancer and pulley were clearly out of true. I then removed both the pulley and the balancer and the hub remained out of true with a noticeable wobble on the face of the hub.

I purchased a replacement and then removed my old one and found a different problem. The woodruff key was mangled. I sourced a new one from BMW (picture comparing new & old below) and carefully checked the machined pocket to ensure it was in good shape. I then partly assembled after carefully cleaning and oiling the front seal.

Once I determined that the original hub was running true I then completed the assembly, torquing the front hub nut and the balancer/pulley bolts. Engine is running again and I believe idling much more smoothly.

I know that I would never have assembled with a bad woodruff key, so my assumption is that the key moved during assembly, but I am not sure how that happened.

 

[sfdon]

Those keys are notorious for shifting on the shaft