S2 - Noise Under Bonnet, Sounds Like Metal Tapping...

[pixel8r]

Hi guys,

Just bought a 2000 Nissan Stagea (106000kms, has just had major service - i have the papers etc) from a dealer and its in near-perfect condition inside and out, runs really smooth etc except for one thing.

When the car is under heavy boost (over 50-60% throttle, 3500+rpm) it makes a metallic kind of sound that seems to be coming from directly in front. The turbo spools up ok, and the noise only starts near or past full boost so I dont think the turbo is the culprit.

My first instinct was to suspect the turbo but the noise isn't coming from where the turbo is, it seems to come from the top of the engine.

Something like T-T-TTT-T-T sort of noise. It only has a 1/4 tank of fuel left, and is a fresh import...so its probably been sitting in the yard for ages with next to no fuel in the tank...maybe pulling up crap off the bottom of the tank too??

I plan to put a full tank of 98 in and see if the problem goes away.

If it doesn't, my guess is coilpacks, or spark plugs. Can I rule these out, based on what I've said above? The spark plugs should be new since its just complied.

I always thought pinging would sound more like a rattle (like a chain rattling on metal), but I've also heard it described as ball bearings on tin...which is closer to what I'm hearing.

I do have dealer 3 month warranty to fall back on...but if its just the fuel causing it then it isn't a warranty issue.

What are your thoughts?

Edited March 1, 2011 by pixel8r

[Sunkist]

apprently nails on a tin roof sound is detonation. not a good sign.

fact that its happening on boost is also a worry.

change the fuel. if it still does it. take it back asap as within 30 days of yard warranty, they must fix everything as they have provided a Roadworthy.

[pbk1776]

Agree - bring it back - might be the turbo is giving way already

[pixel8r]

If it was the turbo the sound would be coming from closer to the passenger footwell. Also, turbo sounds are more like either a whistle, whine or a screeching noise. This sound is neither of those.

This sound is definitely central and directly in front, so I'd say its pinging.

It makes sense that it would ping under heavy load and not when cruising...nothing alarming there. If its going to ping at all, that is when it will do it.

If fuel doesn't fix it, I will be taking it back asap.

[Sunkist]

your right, could be expired fuel causing it. pinging detonation pinking and other stuff is fairly dangerous.

refuel asap.

[pipster11]

i'd say coils

they will die at max torque (which is when you get max cylinder filling = max air/combustion stroke) which would be also just as you ramp onto boost (3000-5000 rpm)

[pixel8r]

i'd say coils

they will die at max torque (which is when you get max cylinder filling = max air/combustion stroke) which would be also just as you ramp onto boost (3000-5000 rpm)

max torque is 3200rpm. boost starts ramping up around 1800rpm - its all factory.

Taking it back today for them to have a look.

[pipster11]

max torque is 3200rpm. boost starts ramping up around 1800rpm - its all factory.

Taking it back today for them to have a look.

yeah but you only start getting near the peak at 3000 rpm, mine is nearly all factory

you'll probably see coils breaking down at lower revs in a stagea too, compared with a skyline due to the extra load on the motor

[SMOKEYV35]

coils breaking down should result in a 'missing' sound - a shuddering and a loss of power.

i'd say its pre-detonation. i wouldn't be 'experimenting' with the sound trying to work it out if i were you. your best insurance is to go to the servo and buy a bottle of octane booster - dump that in, fill the rest up with the highest octane petrol you can buy, run that through and fill it up again - if it still does it then you need to get it on a dyno and tell them you need an AFR check, that you're worried about detonation and get them to run it up carefully.

if it is pinging it could be something as simple as the timing being out. either way, if it IS pining, i highly doubt its covered under a statutory warranty - it's not a roadworthy item.

[pixel8r]

coils breaking down should result in a 'missing' sound - a shuddering and a loss of power.

i'd say its pre-detonation. i wouldn't be 'experimenting' with the sound trying to work it out if i were you. your best insurance is to go to the servo and buy a bottle of octane booster - dump that in, fill the rest up with the highest octane petrol you can buy, run that through and fill it up again - if it still does it then you need to get it on a dyno and tell them you need an AFR check, that you're worried about detonation and get them to run it up carefully.

if it is pinging it could be something as simple as the timing being out. either way, if it IS pining, i highly doubt its covered under a statutory warranty - it's not a roadworthy item.

hmmm dont like the sound of that last bit. we dont have roadworthy certificates here in SA...but I assumed the main car mechanicals were all covered, at least so that the car is running as promised.

I wont be pushing it - it drives fine unless I put my foot down a fair bit. I'm gonna put 98RON fuel in, then take to the dealer for them to have a look. I need to go there anyway to pick something up.

[66yostagea]

You mentioned a "FULL SERVICE" Was the timing and all other belts replaced. And how about the idler and tensioner pulleys also the water pump.

I have just been through the misfortune of having the idler pulley seize which in turn delaminated the timing belt. Lucky it did not break, just slipped a few teeth and went into limp mode.

Then when it was put back together someone(?) overtightened the fan belt which caused the water pump front bearing to collapse, then the shaft sheared an the fan unit went beserk and smashed the radiator.

Also the aux. belts had not been replaced.

Total bill was about a grand.

The Stag is N/A and we had the paperwork to say the 100k service had been done, but they only replaced the timing belt.

While all of the above may not be pertinate to your problem, even though the tic tic is up front,

The moral of the story is replace EVERYTHING when doing the timing belt.

[Tangles]

smokey said it all. your description sounds like pinging

get octane boost in (Id use say a 10% mix of eflex fuel, say 6-litres of E85 eflex from caltex) with fresh 60L of 98ron premium unleaded.

run through full tank then do it again.

if you use the E85 as octane boost (ie a 10% mix) then once second tank is run through replace the fuel filter.

then see how it is with a full tank of 98Pulp on full boost.

[wolverine]

Just put fresh fuel in. Simple is best.

[KiwiRS4T]

If that doesn't fix it get timing checked or full dyno test ( timing and afrs). You can easily destroy your engine otherwise.

[pixel8r]

hmmm, sorry, looks like I headed down the wrong path.

On closer inspection, and after putting 50L of 98 RON fuel in, it seems like it may well be turbo related. The sound is actually coming from the passenger side of the motor, not the centre as I first thought.

There is no issue when you rev the engine in neutral (although its not under load that way either), and also the sound is more like a short sharp chisel sound...but there's a slight chirp-kind of sound to it as well - which would have to be metal on metal by my way of thinking. My initial thoughts are the turbo fins _just_ scraping the side of the turbo??

Only happens near max boost, say 2500-3500rpm, and if I lift my foot a little it disappears, even if the revs are over 3000rpm.

The turbo sound is pretty noticeable, but if I remember correctly this is normal for the RB25DET (NEO). There are no squeals or unusual whistles, just this chipping/chirping sound which turns into one long sound if I push it harder (actually, it almost sounds like crickets or cicadas at this point).

Sorry if the description isn't very good - its the best I can think of right now.

I took it back to the dealer and took them for a drive and they heard it but they were saying its just a squeak or rattle. In any case, they are going to get a mechanic to look at it on Monday (I have the car until then) and if its mechanical they said they would definitely cover it.

They also said if there was a problem with the turbo it would make the sound all the time, not just on max boost...but I wasn't so sure on this. I thought if you have some shaft play the fins will start to scrape on the edge before it eventually lets go. Excuse my lack of knowledge if I'm way off track...

[chef_stagea]

The knock sensors are there to throw an engine light at the sound of 'ping' they are tuned to pick up

Those frequenys witch are very unique! Take it back n c wat they say. Hook up a boost gauge and c if its holding, dropping boost... My f*kd coils made this kinda issue and boost needle was moving ~3 pound up n down very quickly

[pixel8r]

The knock sensors are there to throw an engine light at the sound of 'ping' they are tuned to pick up

Those frequenys witch are very unique! Take it back n c wat they say. Hook up a boost gauge and c if its holding, dropping boost... My f*kd coils made this kinda issue and boost needle was moving ~3 pound up n down very quickly

I dont have a guage, but there is no shudder under boost and going by the whoosh of the turbo its holding boost just fine.

Everything I'm reading on the forums is pointing to the turbo blades possibly scraping on the inner wall. Will get them to check the turbo on monday for shaft play...and will take it easy until then. I could check it myself but if they see I've been playing around that could easily affect my warranty claim...so I'll not be touching anything.