engine and drivetrain Alternator bolt keeps breaking!! NEED HELP PLEASE....

[winstontj]

It's #2 in the photo. It lasts roughly 3,000 miles. I have to carry a few spares just incase. What's going on? I have converted (properly) to an E30 alternator. The belt is on only ONE plane, meaning none of the pulleys are off, misalligned, etc. This is really frustrating and completely unacceptable.

I have a stock motor, 32/36, removed waterpump fan, running electric cooler, BMW waterpump, standard E30 brackets, urethane bushings, proper belt tension.....

The only thing I can think of, which is a different issue, is that my motor runs really rough when it idles. I mean REALLY ROUGH. It shakes a bunch and I have no idea how or why. The innards of the motor are completely unknown but mechanical dist, engine timed with light correctly, burns oil on decel - plugs reflect this but are otherwise fine, points set correctly, valves set correctly, blue coil, bosch wires.... think that's it. Everything runs and drives fine except it shakes like the dickens when it's cold and idling. I get 30+mpg (3.45rearend) so I know it's tuned right and the needle sits at 3 o'clock thanks to Curt's amazing radiator.

Any thoughts would be appreciated. I'm sick and tired of spending $3/bolt!!! It's breaking right at the threads, the BMW bolts break where the threads meet the shaft, and the other bolts I buy usually break at the nut. The only thing I can think of is vibration combined with heat, which should not be an issue.

Using red loctite torquing to 18 foot-pounds with torque wrench, every time.

TIA,

TJW

[Benz02]

The bolt's probably breaking because of the excessive vibration as you suspect. When I bought my current 02 it was shaking like crazy and I thought it was a motor mount (which could be your problem). It turned out to be a leaking vacuum hose from the master cylinder and a tight valve on the number 4 cylinder. So, maybe try checking for vacuum leaks and your motor mounts.

[winstontj]

I'm experiencing a slight surge with depression of the brake pedal. I've adjusted the valves obsessivly and nothing seems to have changed. I have even recently replaced the eccentrics and just yesterday checked the tolerances. My brake booster line looks as though it's from 1930 so it wouldn't surprise me if that could be some of the cause. Motor & tranny mounts are new as of January 2006. All of the other vaccum hoses and tubes have been closed up. Also new intake gaskets as of January as well.

Thanks - I'll order a new brake booster hose ASAP for the engine. This shaking has GOT to stop!

EDIT: the .2 mm feeler will not fit but the .15mm feeler does - just want to double check that my Haynes Manual is correct. I think CD said .06"??

[cj]

If it's breaking at the threads, my first suggestion would be to make sure the bolt is'nt bottoming out on the shank or shoulder (non-threaded area of the bolt) when it's tightened. What grade bolt are you using?

If the motor is shaking, tune it. Recheck for things like vacuum, idle speed, valve adjustment, etc. Unfortunatly it's pretty difficult to diagnose without actually being able to see and hear things. Are you checking the adjustment hot or cold?

Cris

[JohnW]

Check you motor mounts/check subframe to make sure it's not cracked.

Funny, I just broke my alternator bolt today (the long one that goes through the top on the engine side; broke on the threads as well. Mine broke because I was having to over-tighten it to get the belt to align semi-properly (320i conversion)).

[winstontj]

Valve adjustment: COLD - or ambiant air temp at about 85 degrees. Valves are adjusted properly. Bolt is breaking at the shank/shoulder but the nuts are not bottoming out. Torquing to 18lbs, using red loctite and the past two times I've found the nut with threads sticking out on both ends. Using BMW parts from the dealer - assuming the grade is appropriate. Subframe was off the car when motor and tranny swap was done in January 2006. No cracks, all new mounts, everything is good on that end....

[Guest Anonymous]

pull plugs wires off one at a time at cap to find which cyl.

[winstontj]

How does one get a dead cylinder and what can be done to fix it? I'm rebuilding a motor now but it's going to take a few months before it's done. Does this mean I'll need to speed up the rebuild?? Is it easily fixable?

[Arizona02]

internal vacuum leak. Any dead can be dead at idle low /rpm from low compression, say under 100 psi. Cyl can make decent power at mid to higher rpms and you wont feel it when driving. Reasons a cyl may have low psi show up on compression test,due to rings not sealing, valves nneding valve job, leaking head gasket. That is along as the cyl is getting proper fuel & spark

[cj]

Inspect the valve springs for any breaks.

Cris

[winstontj]

u serious? why?

[cj]

A broken valve spring will not allow the valve to make a proper seal on the valve seat. The result is low compression.

Cris