QuestionQUESTION: hi i just bought a 2007 miata from dealer with 16k miles in pristine cond. i noticed when i start the car after sitting all night the clutch when depressed at idle and the car not moving is very quiet. when i let it out with the car not in gear it seems to make a little noise. when the car is warm the noise is gone. is this normal? the clutch grabs fine no shudder or slippage otherwise. also the reccomended octane is 91; some people say 87 is fine; others swear its 91; whats the deal? thanks
ANSWER: Some sound is common from the clutch centrifugal, springs and input shaft of the transmission. When you hold the clutch depressed the disc and input shaft stop spinning. When you release the entire assembly including input shaft and the main drive gear of the transmission begin to rotate. Since the center hub and the outer disc plate move on each other and is supported by springs they can oscillate and thereby some sound is made. Sometimes a faint dieseling sound or a faint shuttering. Temperature can have an affect on the type of sound. The bell housing is aluminum and being cavernous can amplify the sound of these parts.
Now if the sound is a squeal or squeak this could be signs of a clutch related bearing issue, however not at 16k, maybe at 116k.
When in doubt have all fluid levels check including the transmission which will be an over flow fitting on the side of the gear box. In all likelihood, nothing to be worried about.
service@miatashop.com
"when your good at what you do, you should be well paid"
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QUESTION: thanks for the fast reply; you hit it right on the head; sort of a spinning sound like you described but i also thought it was probably nothing. but i just wanted to make sure anyway.sound goes away in 5 mins anyway. how about your thoughts on the octane issue that i previously asked? thanks again. by the way i read your posts every day and you really know your stuff. great talking to a pro like yourself.helps us weekend mechanics a great deal. RON
AnswerIt depends on where you live and drive as to which is the best choice. Mazda recommends 91 octane. The engine in your Miata (MX5) has been tuned to create power from a small package thus putting it more in the performance world less in the economy world. Now, the ECU monitors fuel, air, ignition and exhaust and makes constant adjustments to maintain peak levels of efficiency on all fronts with economy and emissions getting the lion share of attention. (thanks EPA)
My suggestions;
If you live at or near sea level, run mid grade or premium around town. Start and stop and heavy loads are where it needs the octane the most, this helps avoid detonation issues. If your heading out on a road trip run low grade unless your climbing in altitude. If it's flat level terrain near sea level your good, the computer will adjust the systems to compensate.
If at anytime with low grade you hear knocking or anything remotely closed to it, put in some high test.
service@miatashop.com
"if your good at what you do, you should be well paid". Or at least well fed.
