Sau Lend Me Your Ears! Rb25 Noise

[gotRICE?]

Hi guys,

I have had a wierd noise in/on/around my RB25DEt for a while but never got around to do anything with it so 1st off ill explain.

Sepc (if it matters)

1998 R33 GTS25t

59,000km

Stock dump > 3" HKS Front > Decat > HKS Hi-Power Silent Catback

R32 10psi Actuator with stock solenoid removed

Apexi Panel filter

Blitz LM FMIC

This noise only EVER occurs at cold idle. And when i say cold, i mean the block has to have no heat in it at all. So its generally an overnight thing. The next time its started it does it.

It does not ever do it once there is a bit of heat in the engine. So to overcome it i generally let the car warm up for a few mins or so before i drive it. Other than this. Everything sounds/runs mint.

Engine runs strong, never misses a beat. Runs great on the track and drag strip.

And when on a long run, apart from the exhaust you would swear it isnt even idling (when stopped) it is so quiet. Sounds amazing.

So heres the noise. Can anyone identify it? Is it "normal"? Does anyone else have the noise?

The noise is clearly obvious. And it does it anywhere from 1200rpm > 1500rpm. Anything more/less its not there.

A friend of mine on this forum, his RB25DEt also does this, but it is very quiet. Still noticeable, but compared to his mine is like a megaphone is attatched to it.

Can anyone recommend anything?

Thanks in advance for the help. As the noise does bother me.

Edited January 20, 2009 by gotRICE?

[The Dan]

Timing belt

Timing belt bearings

Water pump

Alternator bearing

VCT camshaft pulley dry

Could be any of these things and more. When was the last time the timing belt was done? and if it was supposedly done before you bought it, just say NFI.

[Strik3r]

hmmmmmmm.. sounds a bit like piston slap (piston slapping against the side of the bore while cold) but that shouldnt happen in a standard internals engine.. could be something at the little end of the rod... it doesnt sound quite like big end knock.

[Strik3r]

not block noise Dan ?

[gotRICE?]

Timing belt

Timing belt bearings

Water pump

Alternator bearing

VCT camshaft pulley dry

Could be any of these things and more. When was the last time the timing belt was done? and if it was supposedly done before you bought it, just say NFI.

NFI, but i would imagine it hasnt been done since i bought it at 48,000km 1st owner in NZ.

I guess it could have done a million KM from Japan, but the overall appearance of the interior/exterior/seats/underbody would suggest its fairly genuine.

Only way to figure what one it could be would be by changing each one i guess... And does this mean that these problems could become less apparent when they are warm?

[sly32]

NFI, but i would imagine it hasnt been done since i bought it at 48,000km 1st owner in NZ.

I guess it could have done a million KM from Japan, but the overall appearance of the interior/exterior/seats/underbody would suggest its fairly genuine.

Only way to figure what one it could be would be by changing each one i guess... And does this mean that these problems could become less apparent when they are warm?

if its internal and as the car gets warm it goes away it would lead me to believe its to do with the cams and oil, i dont think its internals though, internals normally make a bigger sound,

as for mentioned about about the water pump and alternator etc... i think these are on the right line, one way to check, take the belt of alternator and start the car, if there is no sound, its either you water pump or alternator, try those different things

[The Dan]

not block noise Dan ?

Yeah, you are right Gervaise.

I had another listen to it and it does seem like a forged piston rattle. Nothing serious if it's forged pistons inside but I would definitely be making sure you have it running for at least 2 mins before you drive it from cold.

[Lithium]

You heard mine aye Bevan? Makes a noise of sorts though I think mine is quieter, was it the same thing? Mine has been doing its noise since I can remember (I remember panicking about it in 2005 when I noticed it from the outside of the car) but 4 years, >60,000km and 100kw on its still fine lol.

Edited January 20, 2009 by Lithium

[gotRICE?]

Thanks guys

I will give the alternator trick a go and see what happens next time its cold cold.

Then i will think about doing the waterpump/cam belt etc..

I use Motul Turbolite oil. Seems to do the trick. But have recently sourced Royal Purple for a pretty good price so might switch to that next.

I wouldnt know if its forged but i highly doubt it as i bought the car stock standard. So hope its not piston slap!

And yup, was yours Dan my man. I mentioned it when we did the coilpacks. Will give these things a try.

[rob82]

Sounds like piston noise to me as well - maybe a shrunk piston skirt.

[QUICKY]

mate i personally think it sounds like lifters/tappets. the fact that it goes away once u rev it past 1500rpm and also goes away once the motor is warm would suggest to me its lifters/tappets. try using a thicker oil on ur next oil change annd it should hopefully do the trick

[The Dan]

mate i personally think it sounds like lifters/tappets. the fact that it goes away once u rev it past 1500rpm and also goes away once the motor is warm would suggest to me its lifters/tappets. try using a thicker oil on ur next oil change annd it should hopefully do the trick

Yeah still a bit deeper in pitch than a lifter noise. Usually lifters are a higher pitched tapping noise. You could be right though, it's so hard to tell these things when all you have is a youtube video. I hope is something simple. It's never nice when you find gremlins in your car.

[GTS4WD]

Hey guys..

Re-hashing old thread!

Any news on what this noise could be?

Have the exact same noise in a S2 Rb25DET

[SATO GTS]

sound's like a big end rattle to me, especially when its only happening just of idle.

[GTS4WD]

After some research - Piston slap

[gotRICE?]

Im still stumped.

Noise is still there at the same interval, Cold start, around 1500rpm. And still stops as soon as it starts to warm.

Car still makes fantastic power, and is regularly tracked/drag raced. Drives perfectly...

Switched to Royal Purple Oil/filter's last change and no effect.

Still have my stock pile of waterpump/belts/ tensioners etc. Just havnt got around to getting it done yet ha. Fingers crossed its still one of these.

If not... i guess one day it will go boom.

[nick81xd]

sounds like timing belt is way too loose. if you dont know when it was done last put a timing belt kit in it

[gotRICE?]

Yeah i have a kit, have had for a while, just finding the time to get it in

I bought the car at 48,000km, so at a guess its the original one.

[Lithium]

Mine has done it for a good 70,000kms so far - maybe more... I lose track. I am pretty sure I first noticed it in 2005. Since then its seen track time, god knows how many drag runs (a good number of which reasonably into the 12s) , dyno runs, street driving, compression tests (with good results), 3 different turbos, up to 20psi of boost, a new cam belt and it seems no louder than it was when I first noticed it.

I have no idea what it is, but am pretty sure that if it was bearing noise or a damaged piston skirt I'd have known about it by now!

[aleks]

get a stethescope with a metal tube end, find out where the noise is coming from....