Whining NB8a

Engines, Transmissions & Final Drive questions and answers

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manga_blue
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Re: Whining NB8a

Postby manga_blue » Fri Aug 16, 2013 4:19 pm

wiz043 wrote:I may need to take it back and get it adjusted but I was under the impression that the adjuster pulley did this automatically??
No, one of the idler pulleys has a spring tensioner which is meant to give you an initial adjustment close to spec but the belt needs to be manually adjusted and locked there after that. Possibly your mechanic relied on the spring alone. Here's the full process from the Mazda factory manual for him/her.

Image

It's stupid because generally you can do a better, faster job by not fitting the spring at all.
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wiz043
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Re: Whining NB8a

Postby wiz043 » Fri Aug 16, 2013 6:41 pm

Thanks for that manga_blue.....I have printed those details out and I will pass them on to the mechanic mainly for the top deflection measurement if I need to get it loosened down the track.

Much appreciated.... :wink:

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Re: Whining NB8a

Postby Mr Morlock » Sat Aug 17, 2013 1:33 pm

manga might comment. Since the the deflection can be checked from the top that should readily indicate if it is overtightened and that is easy to access. I guess if its like a violin string it would not be a good thing. The other things already replaced seem almost certainly point toward the belt being the cause of the noise.

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Re: Whining NB8a

Postby NitroDann » Sat Aug 17, 2013 1:37 pm

wiz043 wrote:
sailaholic wrote:It's fine to re use a cam cover gasket if it's reasonably new.

Sent from my GT-I9100 using Tapatalk 2


Yeah....I know but it wasn't the cam cover gasket, it was the rocker cover gasket, and the new one was apparently damaged when it was stripped down for the second time as it started leaking so I had to fit another new one. sob..... :evil:


Cam cover, rocker cover.. Same thing.

Why not just leave it? Can you even hear it from inside the car?

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manga_blue
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Re: Whining NB8a

Postby manga_blue » Sat Aug 17, 2013 3:36 pm

Mr Morlock wrote:manga might comment. Since the the deflection can be checked from the top that should readily indicate if it is overtightened and that is easy to access. I guess if its like a violin string it would not be a good thing. The other things already replaced seem almost certainly point toward the belt being the cause of the noise.
That's true. In fact he can check it without ever going anywhere near that mechanic again, providing it doesn't need further adjustment.

Just reading back through the thread I realise there's also a worrying mention in the first post about looseness in the crank pulley after the belt change. Apart from the likelihood that this causes belt vibration, and hence belt whine, it is the single most common cause of failure of these engines. The loose pulley must be sorted.

This means that so far this routine job has resulted in a loose crank pulley, an indeterminate whining noise at the front, a damaged cam cover gasket and at least 2 repeat visits. When jobs go bad like this you get stuck with that nasty choice about whether you take work back to the same mechanic for rectification and risk further damage or do you just cut your losses and go to someone more competent.
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Re: Whining NB8a

Postby wiz043 » Sat Aug 17, 2013 7:37 pm

NitroDann wrote:
wiz043 wrote:
sailaholic wrote:It's fine to re use a cam cover gasket if it's reasonably new.

Sent from my GT-I9100 using Tapatalk 2


Yeah....I know but it wasn't the cam cover gasket, it was the rocker cover gasket, and the new one was apparently damaged when it was stripped down for the second time as it started leaking so I had to fit another new one. sob..... :evil:


Cam cover, rocker cover.. Same thing.

Why not just leave it? Can you even hear it from inside the car?

Dann


Sorry, I thought he was referring to a gasket on the cam belt housing and, yes, you can hear it inside the car at low speed. I am going to leave it for a while in the hope that it gradually dissipates as the cam belt wears in and stretches a bit. From what I understand different brands of cam belts for these cars can cause this noise even if adjusted correctly.
Thanks for help.

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Re: Whining NB8a

Postby wiz043 » Sat Aug 17, 2013 7:41 pm

manga_blue wrote:
Mr Morlock wrote:manga might comment. Since the the deflection can be checked from the top that should readily indicate if it is overtightened and that is easy to access. I guess if its like a violin string it would not be a good thing. The other things already replaced seem almost certainly point toward the belt being the cause of the noise.
That's true. In fact he can check it without ever going anywhere near that mechanic again, providing it doesn't need further adjustment.

Just reading back through the thread I realise there's also a worrying mention in the first post about looseness in the crank pulley after the belt change. Apart from the likelihood that this causes belt vibration, and hence belt whine, it is the single most common cause of failure of these engines. The loose pulley must be sorted.

This means that so far this routine job has resulted in a loose crank pulley, an indeterminate whining noise at the front, a damaged cam cover gasket and at least 2 repeat visits. When jobs go bad like this you get stuck with that nasty choice about whether you take work back to the same mechanic for rectification and risk further damage or do you just cut your losses and go to someone more competent.


I am no mechanic obviously, but how can you check the slackness or otherwise of the cam belt from the top without dismantling everything?

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Re: Whining NB8a

Postby NitroDann » Sat Aug 17, 2013 7:56 pm

Remove cam cover (takes about 2 minutes).

Push down on belt with finger.

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Re: Whining NB8a

Postby wiz043 » Sun Aug 18, 2013 11:33 am

NitroDann wrote:Remove cam cover (takes about 2 minutes).

Push down on belt with finger.

Dann


Thanks......I did not realize that the rocker cover/cam cover went over the top of the cam belt also and was in one piece.

I removed it and there appears to be enough slack in the belt at the top (1/4 to 1/2 inch) so the only thing I can put it down to is the particular belt brand. I will just drive it for a while and see if things improve.

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Re: Whining NB8a

Postby NitroDann » Sun Aug 18, 2013 11:44 am

It should deflect 10mm with 10kg of downward force, so in other words if you can get it to move a half inch with all your might its ok.

If the teeth profile dont match 110% you will hear it, honestly, just get an intake and a big exhaust and you will stop noticing :P

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speed wrote:If I was to do it again, I wouldn't even consider the supercharger.

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Re: Whining NB8a

Postby wiz043 » Sun Aug 18, 2013 11:55 am

NitroDann wrote:It should deflect 10mm with 10kg of downward force, so in other words if you can get it to move a half inch with all your might its ok.

If the teeth profile dont match 110% you will hear it, honestly, just get an intake and a big exhaust and you will stop noticing :P

Dann


Ha-ha....yeah, but it would be much cheaper just to turn the radio up. :P


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