Noise from engine bay when slowing down

[Boomerjake]

Hi Guys
I know I have mentioned this issue before on a thread but I hope I can discribe the issue a little better and someone can help me. Even asked local Honda dealer but as it does not always make the noise- and it did not for them , they could not help.
I would discribe the noise as a very fast whirring sound which comes from the engine bay (within the first 10 minutes of driving and then does not happen again). It happens when I have been at around 4000RPM (or above) and I am de- accelerating or braking, when I tap the throttle it will go away. My car is an auto and I dont know if it is something linked to that.
After the first 10 minutes the car runs 100% ok.
Has anyone got any ideas what it could be- and a solution.

Thanks

[Problem Child]

Hi Guys
I know I have mentioned this issue before on a thread but I hope I can discribe the issue a little better and someone can help me. Even asked local Honda dealer but as it does not always make the noise- and it did not for them , they could not help.
I would discribe the noise as a very fast whirring sound which comes from the engine bay (within the first 10 minutes of driving and then does not happen again). It happens when I have been at around 4000RPM (or above) and I am de- accelerating or braking, when I tap the throttle it will go away. My car is an auto and I dont know if it is something linked to that.
After the first 10 minutes the car runs 100% ok.
Has anyone got any ideas what it could be- and a solution.

Thanks

I dont know the answer to this problem as it is not the one I encounter. I get a high pitched squeeling from the passenger seat when I accelerate or corner sharply....especially if the missus is in the car!

[Kaz-kzukNA1]

Hi, Boomerjake.

Could you provide us with any info about your NSX including any modifications?
Also, any chance of recording the noise?

Does it happen if you stop the engine, re-start and drive again?
Does the noise change with the A/C On or Off?
Can you re-create the same noise by just starting the engine, keep it in P range and rev it above 4,000rpm within the first 10min?

Any further info will help.

Kaz

[Boomerjake]

Hi Kaz
My car is totally unmodified, I will go out in the car this weekend and try to record the noise.
The noise can happen if I stop and restart but mainly happens in first 10minutes of use. I always let the car warm up before I drive and the noise does not happen until the car is in gear, the noise sounds like a very fast spinning noise and happens when I take foot off accelerater, if I dab my foot back on the accelerator the noise stops (but may come back until I come to a stop) then the noise usually will not happen again even if I drive for more than an hour. Aircon has no effect on whether the noise happens or not

Hope you can help
Greg

[Boomerjake]

Hi Kaz
I took the car out today, and as usual the noise happened when I slowed down, the difference this time was a cruntching noise (gearbox), so as mine is an auto I selected 3rd and everything was ok. After doing a few things with the gears - 1, 2 and 3 seem to work fine when selected. When I put it in D it is fine until it goes into 4th then the crunching sound happens. Any ideas of what has broken?

Hope anyone can help

Greg

[Kaz-kzukNA1]

Hi, Greg.
Could you kindly clarify the following points in order to assist you better?

1. Year model or first part of the VIN.
If you are 100% sure of your year model, please let me know.
Or, please tell us only the first 6 digits of the VIN after JHMNA1-.
Please do not mention your full VIN on public website.

2. Total mileage
What is the total mileage at the moment and do you have any idea on when (**months/years ago) or at what mileage you started to notice the issue?

3. Post #1 VS #5
In post #1, you mentioned that you got fast whirring noise that comes and goes under several conditions but after driving for 10min, it sounded like the noise never came back for the rest of the journey.
In your last post #5, it sounded like addition to the above noise, you experienced crunching noise only when in the 4th gear.
Is this correct?

Does the crunching noise happen ONLY when you are decelerating/braking or does it happen even when you are accelerating or cruising?
This is to understand whether it is the different issue or not from the one you mentioned in post #1.

Does this crunching noise disappear after driving for 10min like in your post #1?

Kaz

[Boomerjake]

Hi Kaz
Thanks for getting back to me, I am hoping you can help diaganose the problem.
Just to answer your questions first
I belive the car to be a 1991 with the next 6 numbers on the VIn are 2600T0
The mileage is currently at 47200, I have owned the car for about 18 months and noticed the noise about 6 months or 400 miles ago.
As far as your question on the noise goes my answer is as follows, the initial noise from post 1 has now become the crunching noise in post 5. What I mean is that last weekend the car was about to make the spinning noise (which it had been doing for previous 6 months which normally happened once and bnever came back during that drive ) but then started to make like a metal on metal crunching noise. I then changed gears as in post 5 which made me identify that it happens when on D position on the change up to 4th (and I guess it was making the spinning noise previously when I was deaccelerating in 4th gear). I have been afraid to drive the car since in case I do any damage
If you have any other info you require please let me know and I will supply what ever I can
Thanks

Greg

[Nick Graves]

First thing; when did you last change the tranny fluid & what colour is it?

If in doubt, a couple of litres of ATF isn't expensive as a try-out.

[Boomerjake]

Hi Nick
Just looked at the oil level and it looks up to the normal level and oil is clear red in colour.
Anyone got any other ideas

Thanks

Greg

[Kaz-kzukNA1]

Hi, Greg.
Based on your partial Vin info, I can confirm that it is indeed 91 AT model.
As it is the UK based model, I would be surprised if you are experiencing AT gear slip at your mileage.


In Japan, for most of the AT owners driving within/around the busy city area, they will start to feel slip mainly at 3rd - 4th upshift at about 60K miles.

Please note that there is a huge difference in driving condition between Japan and UK.
As a comparison, most of MT owners including myself are replacing the CL disc every 30 - 35K miles if mainly used on the busy city area in Japan.
There are lots of steep hill even in the city area, many traffic lights, consistent traffic jam, etc so it’s always like stop and go driving style.

I haven’t changed the way on how I engage the CL from when I was in Japan and under UK driving condition, I can easily cover more than 100K miles on OEM CL compared to when I used to replace it every 31K miles in Japan.


Do you feel any slip on partial throttle up shift?

Good situation is on a straight street, you have stopped at the light. Green light so just press on the TH pedal gently and without lifting the pedal, accelerate as you normally do when driving on the street and let the AT controller to shift up rather than forcing the upshift by lifting the TH pedal a little.
If you don’t feel any slip on each upshift, your AT gears would be fine.


Honda AT is quite different from other manufactures using planetary gears.
Each gears have multiple friction discs (like CL on MT model, it’s more close to the DF multiple discs on our NSX) submerged in the ATF.
AT controller adjusts the hydraulic pressure by predicting the engine torque to achieve ideal slip at multiple discs before engaging to the next gear.
So, unless you are doing WOT acceleration everywhere on the street, it is very likely that you will eventually loose the friction material from the multiple discs in the 3rd gear.
So, Honda AT requires overhaul at some point in order to replace these worn discs.
Otherwise, the friction material that came off from the disc will block the meshed strainer resulting in not high enough hydraulic pressure created and you won’t be able to change the gear or not even able to move the car.


From what you wrote and at your mileage, I don’t think your AT box is in that state yet.
It sounded more like something to do with the LC (Lockup CL) system in the deceleration mode.
You may want to have your NSX flatbedded to Norton Way or somewhere with AT experience because it seems that you can now re-create the same issue every time.


By the way, how did you check the ATF level?
As you mentioned that the fluid colour was clear red, you may not need to check it again but you should check it after you drove the car for a while and immediately after stopping the engine (like within 60sec).
Otherwise, it won’t show the correct fluid level.

Kaz

[Boomerjake]

Hi Kaz
Thanks for the reply, I think I get what you are saying, one thing I did notice since I had the car is that when accelerating hard when the auto gear box upshifts it does feel as if it slips slightly (or over revs a little)), is this what you mean by slippage.
Do you know of any local specialists in the soutwest (i am in Bristol), we do have 2 Honda dealers but I am not sure they know what they are doing. Additionally what kind of bill are we looking at for repair (ballpark)

Thanks for your help, I am feeling a bit lost due to my mechanical knowledge.

Greg

[Kaz-kzukNA1]

Hi, Greg.
Yes, I think we are talking about the same ‘slip’ but I’m focusing more on the partial TH (mild/gentle acceleration) up-shift and not the hard one like using more than 70% to WOT (100% open).
It’s like driving in the moderate traffic on A road with traffic light and up-shifting in around 10 – 40mph after you stopped at the red light.

If you don’t feel the slip on up-shift like you are getting at the hard acceleration, then your AT box is not at the critical level where you can no longer drive the car due to lack of fluid pressure.

Still, there is something not quite right if you are getting noise only in the 4th gear.
May be flatbed it to Norton Way Honda in Letchworth to get the initial diagnosis although I don’t know how much experience they have with the AT box.

Before doing so, please look for any error codes by shorting the blue 2pin connector and count the flashing ‘D’ indicator in the dash gauge.
As mentioned, the fluid level has to be checked within 60sec after you stopped the engine.
Otherwise, it will show higher fluid level than the true figure.

If it was diagnosed as AT box failure and if it requires OH, then we have our own knowledge source from britlude.
Following post should provide you with some idea on the cost.
http://www.nsxcb.co.uk/showthread.php?10491-My-automatic-gearbox-the-story!-lots-of-pics-too

Having said this, without the actual slip at the partial TH up-shift, your mileage, noise only happens in 4th gear, etc, I never heard of AT box requiring OH with your conditions in Japan.
As far as I know, there are more AT NSX than MT ones in Japan.
Hope it's something related to LC solenoids, etc and not requiring the OH.

Kaz

[Boomerjake]

Hi Kaz
Will check all of the above this weekend
Have you got any contacts at Norton way for me to phone who actually knows about NSX's

Thanks

[Hagasan]

As Kaz might not see this and your still online..... Contact at Norton Way is Bryan Smith, the service manager, Good Luck, Gary
Hi Kaz
Will check all of the above this weekend
Have you got any contacts at Norton way for me to phone who actually knows about NSX's

Thanks

[Boomerjake]

Thanks Hagasan

[Boomerjake]

Hi Kaz
Sorry I have not replied to this thread, I have been away for a couple of months, on your advice above you recomend 'please look for any error codes by shorting the blue 2pin connector and count the flashing ‘D’ indicator in the dash gauge' . What connectors are you talking about as I am a little confused.
Obviously to get the car sent to Norton Way is an option, is there not anywhere nearer Bristol.
Hope you can help.

Greg

[Kaz-kzukNA1]

Hi, Greg. Welcome back.

Please follow the instruction and photos in the following link.
You can also find this in the ‘Sticky’ section of the Technical Forum on our site as well.

http://www.nsxcb.co.uk/showthread.php?9229-How-to-read-the-error-code



Once you have shorted the SCS blue 2pin connector based on above link and turned the IG sw into ON position (but do not start the engine), please pay extra attention to any flashing lights on the dash display especially the 'D' range AT indicator.
Any failure codes stored inside the AT controller will be shown as the number of flashing D indicator.


Regarding the recommended Honda garages around Bristol area.....

I’m afraid I simply don’t have enough personal experience for any services on NSX carried out by any Honda garages within UK as I only used them just once for MOT over the last 16 years.

In fact, I’m helping several Honda garages, non-Honda garages, special tuning shops, etc for NSX issues and based on other owners feedback on this site and also by visiting and speaking to the people face to face, I can only speak from my limited experience and recommend Norton Way Honda in Letchworth.

Probably there are other owners near you so I hope they can chime-in with their own experience but if your issue is AT oriented, then I’m afraid, it is possible that our member britlude may have more experiences on AT box than other Honda garages.....



http://tyiz.jp//NSX/BBS/bbs/data/1379907549.9.jpg?1394453123

http://tyiz.jp//NSX/BBS/bbs/data/1392121836.2.jpg?1394453823

http://tyiz.jp//NSX/BBS/bbs/data/1392121836.3.jpg?1394453823
If your issue is internal AT box failure, unless people has the experience and know-how to this level, it would be better to replace it with an used one as long as it comes with some sort of warranty.

Any way, first thing first, you need to have it diagnosed and find out whether you have AT issue or something else.

(All photos are from Mr. Toyoizumi at KSP Engineering, Japan. Thank you.)

Kaz

[NSXGB]

http://tyiz.jp//NSX/BBS/bbs/data/1392121836.3.jpg?1394453823


(All photos are from Mr. Toyoizumi at KSP Engineering, Japan. Thank you.)

Kaz

That casting is a work of art.

[Boomerjake]

Kaz
Thanks a lot for this, not at home today, but will try it on Thursday when I am back. Fingers crossed that it is not a gearbox overhaul.

Thanks again

Greg