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Discussion Starter · #1 ·
Its not so much a noise but an occurance. At 1900 rpm there is a cruching sound; similar to that of crunching gears. When I rev the engine, as it passes through this range the noise is audible but only at this one, very narrow point on the rev range.

From testing, it isnt always there when the car has just started and in neutral. You cant hear it from poping the bonet and listening but you have to go around to the sides and its loudest under the driver/passenger part of the car.

It cant be (or its not likely to be) anything broken free (ie in the exhaust/cat) or any bolts loose because it is ALWAYS there but only at almost exactly 1900 rpm.

Strange. Any ideas would be appreciated. Im intrigued why it can only be heard at this one rev speed.

?
 

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Could be something to do with harmonics? Mabey your exhaust or similar is resonating at that particular rev range.
 

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I had something similar. I wouldn't say it sounded like 'gears crunching' but it was a an annoying rattle sound at a certain rev range. It turned out that a few of the brackets welded to the cat holding the heatshield on had broken and was vibrating against the cat.
 

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Discussion Starter · #4 ·
Yes, that the noise, a rattling type sound. I couldnt put my finger on it before.

I'll get under the car tomorrow to have a play but was your noise at a certain rev range only or pretty constant?
 

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Discussion Starter · #5 ·
Ok, sorry didnt read the post properly. Ill be ckecking that tommorrow. Initialy I thought maybe it was something broken inside the exhaust system and it was stopped at the cat but this sounds more plausable.
 

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before i even read everyone elses comments, i could straight off say it is something moving in ur exhaust system/cat.if u can take off ur CAT(stock exhaust), do so and give the outside a good wipe down and knock it a few times to let any loose bits fall out.
 

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crusty said:
It could be a heat shield on the exhaust rattling.

Thats what I was basically saying :) The brackets holding the heat shield on the cat had broken and the heat shield was vibrating against the cat.
 

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Discussion Starter · #9 ·
Ok, thanks for all of your help guys.

I decided that today I would check the heatshield of the cat and if I couldn't find anything tommorrow I would take the cat off and give it a good shake (By cat I am refering to a part of my car, not my dear black pet, Puma ;) ); basicaly because I didnt have timeto get the gaskets today. I got underneath and removed the heat shield on the cat and lo and behold, there were some largish (well large for the space they had worked their way into) bitsof gravel. I am/was an Army Cadet and so frequented dirt/gravel roads a fair bit and so I'm assuming that this is how they hve got there.
Trying not to be overly optimistic, I replaced the heist shield sans gravel and started her up. Perfect. No more rattling. So now its all good again.

Thanks all.
 

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great to hear mate. :)

i checked out a manual mx6 '91 today and i was about to buy it for $5000 until i saw a semi-large oil leak. it was the power steering rack leaking. he said it should cost about $300 to get a new one installed. anyone got any idea on this?
 

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$450-$550 for a GOOD job

you can get in done cheaper..... but the place thats doing mine on monday is around $500 and they reco my local mazda dealers racks

good enough reason for me
 
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