Pump makes humming sound after engine shutoff

[squid2004]

There's a pump (I guess) in the upper drivers side of the engine bay (says Toyoroki on the cap) that hums every 30 seconds or so after I shut the engine off. It's still doing it after 30 minutes or so and I've been having a low battery issue --- I wonder if this is causing it.

Why is this pump "running" or humming even after the engine is shutoff? What does it do and is this normal?


Thanks in advance.

 

[JIMAZ]

Interesting...I have the same problem in my 1997 and have not been able to find the root cause. Does not seem to cause any engine problems (no OBD codes set) and my battery seems fine. I have been trying to debug this for ~8 months and finally gave up. Asked other mechanics very familiar with NSXs and they had no idea what could be causing this humming with the engine off.

My frequency for this humming is every 15-20 mins after the car is shut off. Let me know if you ever figure this one out.

Jim

 

[COS91BB]

This may be a shot in the dark. My daily driver has a humming sound some times. It took me a long time to find it but by chance I removed the gas cap, relived the pressure, humming sound fixed.

The thing was the humming didn’t sound like it was coming from the gas cap and I never have found where it’s coming from?? (It works so I stopped looking)

Dave

 

[ktan]

same here with walbro ... bumping thread as i thought my car was the only car with that noise after shut off!!!

 

[NSXBill2]

I have been hearing it lately. Very faint, but cyclic. Sounds like an air raid siren, but very, very faint. I figured it was cooling system pressure leaking down or something.

 

[comtec]

I wasn't sure excatly where the sound was coming from but where you are talking about is the Fuel Vapor Canister so what dave said makes sense about the pressure in the system. I guess as the pressure in the tank builds, it is being pumped back into the intake as part of the emissions. I don't think this is causing your battery to drain unless your battery is already marginal.

 

[EX_NSXowner]

Same problem with my 1997 NSX - finally sold it last month due to too many electrical problems - which my mechanic believed were all related - including the pump issue. 10 years old... mechanical/electrical things start breaking down - he suggested selling it why i can still get some $ for it -- before serious issues arise and the price for fixing was getting nasty and was only going to get worse.

 

[slamstrom]

My 97 is quiet when the engine is turned off. No strange noise coming from the engine bay. Should I be expecting this soon?

 

[clarknm]

Obviously it's hard to know based on descriptions of sounds, but both of my Acuras have intermittent hums when off. I believe it's related to the fuel pressure system, and the hum is actually building/maintaining the gas tank pressure. That's the reason I've heard for the TL, anyway, but I can't find any documentation to back that up. As far as the 97 having electrical issues..sorry man, but that's just your car.

 

[comtec]

My 97 is quiet when the engine is turned off. No strange noise coming from the engine bay. Should I be expecting this soon?

The noise is very faint. If my car isn't in the garage or anything else is making noise you can't hear it. It also only makes the sound about once every 5-10 minutes and it only lasts about 1 second so unless you are trying to hear it you may not.



From the service manual

When the fuel vapor in the tank is higher than the set value of the valve it opens and regulates the flow of fuel vapor to the canister. The canister purging is accomplished by drawing fresh air through the canister and into a port on the throttle body. The purging vacuum is controled by the purge control diaphragm valve and the purge cut-off solenoid valve.

So i wouldn't be worried that you might start hearing it. It seems to be a common thing to a lot of our cars and i don't think it is a problem, the device appears to be working as intended.

 

[squid2004]

I wasn't sure excatly where the sound was coming from but where you are talking about is the Fuel Vapor Canister so what dave said makes sense about the pressure in the system. I guess as the pressure in the tank builds, it is being pumped back into the intake as part of the emissions. I don't think this is causing your battery to drain unless your battery is already marginal.

Great thread responses and thanks for the help, makes me feel better. Yeah, my battery was finally shot (date marked 1996 on Acura battery!!! ) ... got a diehard gold, fit perfectly, no problems with drainage even after a week of sitting.

 

[PhiAlpha44]

Same problem with my 1997 NSX - finally sold it last month due to too many electrical problems - which my mechanic believed were all related - including the pump issue. 10 years old... mechanical/electrical things start breaking down - he suggested selling it why i can still get some $ for it -- before serious issues arise and the price for fixing was getting nasty and was only going to get worse.

That's just rediculous. I've got a 91 with ZERO issues. I think if I was having the same problem, I'd just get it fixed knowing it would be another 10 years + before I had to deal with it again.

 

[comtec]

That's just rediculous. I've got a 91 with ZERO issues. I think if I was having the same problem, I'd just get it fixed knowing it would be another 10 years + before I had to deal with it again.

I have never heard of a NSX with bad electrical problems. Funny he had all those problems but never posted for advice on what to do. Or maybe he didn't find the site untill after he sold the car, RIGHT.


BS

 

[squid2004]

Same problem with my 1997 NSX - finally sold it last month due to too many electrical problems - which my mechanic believed were all related - including the pump issue. 10 years old... mechanical/electrical things start breaking down - he suggested selling it why i can still get some $ for it -- before serious issues arise and the price for fixing was getting nasty and was only going to get worse.

Great first post

Let me guess, did you sell it to the "mechanic" for a really cheap price? I'm sure he was happy to take it off your hands. Even though your story is total BS, I'm glad to see that hypothetically someone who gave a rats ass about the car is now the owner.

 

[brandonsan]

The humming you guys describe sounds like the EVAP system doing a self test or it could be what comtec posted in # 10. It is NORMAL operation and does not require a repair.

 

[brandonsan]

Same problem with my 1997 NSX - finally sold it last month due to too many electrical problems - which my mechanic believed were all related - including the pump issue. 10 years old... mechanical/electrical things start breaking down - he suggested selling it why i can still get some $ for it -- before serious issues arise and the price for fixing was getting nasty and was only going to get worse.

You sold the car and you are just now joining prime ?

 

[SWIFTVISION]

My NSX does this too....with no key in the ignition.

 

[bngl3rt]

I have never heard of a NSX with bad electrical problems.

Bump from the dead... mine has its share.

Biggest one was a frayed alternator output wire extension left over from a CTSC install, getting trapped and shorting under the intake manifold.

 

[comtec]

Bump from the dead... mine has its share.

Biggest one was a frayed alternator output wire extension left over from a CTSC install, getting trapped and shorting under the intake manifold.

You can't blame the car for that. That is a fault of the modifications and the shade tree mechanic or sub par shop doing the removal. The car is very reliable in it's oem form.

Mike

 

[NSXBill2]

As long as we're bumping...

I still hear the sound on cool-down...faint, not irritating or anything, BUT my battery does seem to run down, in fact it is dead currently after only a couple of weeks. My battery always runs down on the NSX. I use a trickle charger, which does the trick of keeping it ready (when I remember to plug it in), but I have many other vehicles that are started just as often and their batteries don't run down at all. Keep in mind, this is over many years of experience with many different batteries. Always wonderd...it seamed to have some kind of current leak running the battery down. This quote below from a post above (which i didn't notice 5 years ago -- time flies) notes that a solenoid is involved...presumabley battery powered...hmmm.

[From the service manual:
"When the fuel vapor in the tank is higher than the set value of the valve it opens and regulates the flow of fuel vapor to the canister. The canister purging is accomplished by drawing fresh air through the canister and into a port on the throttle body. The purging vacuum is controled by the purge control diaphragm valve and the purge cut-off solenoid valve. "[/QUOTE]