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Discussion Starter · #1 ·
So it's been cold lately here in SW Ontario, and I've noticed that my car is now making a hollow-sounding "thunk" when it starts: after a cold-soak, it's taking a fair amount of cranking to get the car to start, and right as the engine catches, the "thunk" sound is heard. Once idling there's nothing but the usual belt squeak, and the car idles and accelerates smoothly. The car has a new battery and starter, and was not making the noise until our recent -20°C weather cwm8

Perhaps related, perhaps, not, there's has also started a "scratching" sound that is audible when the car is idling and when accelerating (off-idle, or when jabbing the throttle while cruising). It sounds very much like what a flywheel sounds like when it scratches a plastic cover (if anyone's ever heard that before, and hopefully someone has).

Any diagnostic help is appreciated!
 

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Discussion Starter · #3 ·
So could that grinding noise be the flywheel on the starter because it's not shimmed correctly? And the "thunk" due to the same reason? That makes sense, but I've had my new starter in for a couple of months now with no noise to-date; perhaps the frigid temperatures have exacerbated an under-shimmed condition?
 

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So could that grinding noise be the flywheel on the starter because it's not shimmed correctly? And the "thunk" due to the same reason? That makes sense, but I've had my new starter in for a couple of months now with no noise to-date; perhaps the frigid temperatures have exacerbated an under-shimmed condition?
metal contracts the colder it is . could be the problem. flywheel is a big piece of metal and starter housing could be closer in the extreme cold.
 

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Discussion Starter · #5 ·
True.
 

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Discussion Starter · #6 ·
Actually, what might make more sense is that the super-cold temperatures have made the grease in the starter’s pinion mechanism stiff, and made it not want to engage/disengage as readily. Is that reasonable?
 
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