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I've just replaced the timing belt and balance shaft belt on a 1990 740 with the 16 valve engine, 128,000 miles on the odometer. I used the write-up at http://www.brickboard.com/FAQ/700-900/B234Ftimingbelts.htm and did not find the job terribly difficult. (Try doing it on a Mitsubishi, where the motor is sideways, and there's barely a fist's width of space in front of the timing cover!) I have a few concerns, however.
First, I was not able to break the oil pump pulley bolt loose. As far as I can determine from the car's service records, the bolt is the original one. Can anyone suggest an alternate way of immobilizing the pulley? I tried wedging it using a long allen wrench, as suggested in the article, but it seemed to have just enough "give" to it to prevent any more torque from being applied to the bolt.
Second, I noticed that the rear timing cover (not sure if this is the correct term - I'm talking about the long plastic piece that fits over the front of the block and head, and into which the three removable timing covers are screwed) is somewhat curled upward, rather than sitting flush, in the area around where the hydraulic tensioner is located. (The cover only seems to be solidly attached to the motor up near the top; the area I'm talking about is just sort of hanging loosely, so there's nothing preventing the curling from happening.) The longest run of the balance shaft belt passes through here, and there seemed to be *very* little clearance for the belt - in fact, it appeared that the old belt may have worn a groove into this area of the rear cover. Is replacement of the rear cover recommended? How much do they cost, and what has to come off the front of the engine besides the cam gears and the various pulleys to do do the job? Alternately, is there any way of "re-flattening" the cover? I thought about trying to use a heat gun or something similar, but was afraid I would do more harm than good.
Third, there is a pronounced whine from the motor. This noise was present before the belt replacement, but seems more prominent now. The article indicates that a "definite whirring sound" is normal from the balance shaft belt at first, and will go away as the belt wears in. How many miles would it typically take for the belt to quiet down?
Any input appreciated.
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