Has anyone experienced this noise?

[comptechnsx]

I know describing noises can be a bit tough,
but I want to give it a try.
First of all, my car is a 91 auto.
When in drive "D" and with my brake pedal engaged, like at a stop light, I hear a "knocking" noise coming from the engine bay. This never happens in reverse, park, or neutral. My tech told me it probably was the ABS pump, but not to worry my brakes work fine. These engines rattle a lot he said.
Just want to know if anyone else had any background with this issue.Thanks

 

[Yellow Rose]

Your tech is snorting something illegal.

The ABS pump is under the front hood.

And no, "these engines" do not rattle.

 

[nsx4fun]

Just a guess, but i would check the motor mounts. If a rubber piece disintegrated from age, etc there might be some metal to metal contact that might make a knocking noise that might not occur in neutral or reverse. Like I said, just a guess.

Fritz

 

[Larry Bastanza]

Fritz,

I totally agree with you about the motor mounts. The procedure to cure this is to LOOSEN the front and rear motor mount bolts. Start the engine and rev it a few times to get the drive train to "rock" back and forth, then retighten the motor mount bolts.

Comptechnsx,

I am thinking based on your description this "knock" occurs then you put the car in "D" correct?

This procedure has cured many "clunking (knocking)" NSX's.

I am thinking the most common way a motor mount would actually be bad is if fluid was leaking onto it and it softened. Not likely in a manual trans car, unless of course you have much bigger problems

, but I am not sure about the automatic.

HTH,
LarryB

 

[comptechnsx]

LarryB

Thanks for the reply, the motor mounts are something I need to have checked out. But, the reason I believe it might have something to do with the brake system, is that the only time I hear this noise is with the brake pedal pushed down. This doesn't happen evryday just after spirited stopping and when I'm stopped on an incline. But I really
appreciate the motor mount idea. Thanks Fritz and Larry B.

 

[MYNSX]

That was my 1st thought motor mounts.
The ABS pump (when and if it sticks) sound very much like a loose belt or bad fan bearing.And in my case it would come and go (cycle)which let me know it was neither.
Supposidly it was initiated by not using the ABS for a period of time .Which reminded me of the time on Mill ave and jammed the brakes to avoid a drunken pedestrian.Mark Basch bled the brakes 2-3 times and the noise has been gone since.

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[comptechnsx]

I think I definately need to do some hard braking and activate my ABS. I can't remember the last time I did that. That might cure it. If not I will put my attention to my mounts.
By the way, I know you are not the only one slamming on their brakes on Mill Ave. I love that street, its crazy sometimes.

 

[Dr.Honda]

Comptechnsx, Is that a single thump just as you engage Drive or a persistant noise? Is there any hesitation to engage or slippage?
I don't think it's the ABS.

 

[comptechnsx]

This noise only happens with my BRAKE pedal engaged. I only hear it when I'm in Drive, not reverse or neutral. Keep in mind this is
When I'm at a complete stop. Standing Still!!
It is not only one "knock", but a continous one until I let off the brake pedal and start off the line. Sometimes it is a faint "knocking" sound other times it is a little louder, quite annoying. I don't think you could even hear it outside the cockpit of the nsx. Any suggestions would be appreciated, thanks JimK.

 

[Lud]

Sounds like a transmission issue to me.

 

[Dr.Honda]

I agree with Lud. I would suspect the torque converter or one of the clutches/pressure plates between neutral and drive. How does the tranny fluid look (emulsified or scorched?) I would suggest you take it to your mechanic ASAP. Good luck