mikstew

I find it interesting that there is so much talk about a "death rattle" prior to IMS bearing failure, yet throughout all of youtube, not a single video of the noise can be found. One possible explanation is that the rattle only immediately precedes failure at which time the opportunity to record it has passed.

I have seen a number of boxsters and 911s with a wide variety of rattling noises, many of which that have been purported to be IMS rattles turned out to be something completely different, including: a ticking lifter, bad input shaft bearing, and a failed dual mass flywheel.

Today, we have a new noise to add to the investigation. This rattle occurs when the car is running at a very low RPM, in gear, under acceleration. For example, any easy way to produce the rattle is in 4th gear at 20 MPH (which puts the car in the neighborhood of 400 RPM). However it is also audible if starting from 2nd gear, or 3rd gear at 10 mph, or any other driving condition causing very low RPM acceleration. The rattle is distinctively diesel-sounding and should not be confused with the standard low pitched thuds of an engine at low RPM struggling for air.

See the video below. Cameramanship is poor since I am driving, thus it is difficult to hear the rattle. The most audible sample can be heard at 1:00.

It is my belief that this noise truly is the death rattle, unlike all the other purported culprits. I welcome everyone else's thoughts or rejections of my theory.

http://youtu.be/gYcPdtE9Gzc

RollingArt

I'd say NOT the death rattle.

What you're hearing is the the sound of someone abusing the **** out of their engine.

Why are you accelerating from 400 rpm anyway? That's a sure way ruin a perfectly good Porsche engine.

The sound is most likely a combination of pinging and rod bearings being beaten to death. So actually, in a way, it is a death rattle. Just not the same one everyone speaks of.

Learn to drive the car properly and maybe the engine will live for a while longer. Hopefully you haven't damaged the rod bearings to dramatically yet. Seriously, what on earth were you thinking?

CW-VIESOCK

Macster

Don't sugar coat it. Give it to him straight.

Ouch.

I agree with your post though the tone is a bit well harsh, but if it gets the point across... the engine of the OP's car owes you a debt of gratitude.

Sincerely,

Macster.

RollingArt

Yes, my apologize to all, especially the OP, for the tone of my post. Think I picked that up from my father. He never minced his words or cut me any slack any time I screwed up.

I was just thinking how pissed I'd be if someone drove MY car that way.

Again, sorry.




Phil

mikstew

Testing driving conditions outside of the normal operating range is NOT abusing the engine, but thanks for the useless input. If I noticed a stumble at 3000 rpm while driving and I wanted to test it by parking the car and revving to 3000 rpm you'd probably cry OMGENGINEABUSE. Don't assume that I drive down the school bus zone in 5th gear every day. I only stumbled upon the noise when missing 3rd gear and instead sliding it into 5th. Believe me, it hurts my soul to drive my car this way. But the ultimate purpose of doing so is to diagnose a potential problem in order to prevent a much, much worse one. I drove it this way twice, on camera, for the explicit purpose of solving a problem, thinking that the friendly and helpful forum members on rennlist would share some insightful thoughts so that I may take the right course of action to correct the problem if there is one.

And no, it certainly isn't pinging. You'd have to be mechanically inept to think that noise resembles anything close to pinging.

txhokie4life

Jake's kit is looking for metal shavings in the oil if the IMS is going.
You could inspect your oil and see if there is any metal particulates in there.

What you are doing to the car sounds like lugging to me.
This could be causing vibrations in your drive train.
Some folks say that modern ECU cars won't lug -- but it sure seems like yours is unhappy.

The lugging could be causing uneven piston detonation.
This could cause some of the chain mechanisms to go taunt then slack and make noise as well.
Basically an uneven, jerky crankshaft movement.

Macster

Driving the car in such a way that the engine rpms are below the idle speed is operating the car, the engine anyhow, outside of its normal operating range.

Just like one would not, should not operate the engine over its redline one should avoid operating the engine under its idle speed.

The idle speed is the lowest speed the engine should operate with little or no load.

At 400 rpms the engine is not making enough power/torque that is required with the tranny in 4th gear to move the car at a steady speed let alone accelerate the car.

The engine in this case is being subjected to lugging. Lugging can be harmful the engine.

There is nothing to be gained by anyone by your operating your car's engine in this fashion.

I would advise you to avoid doing this on purpose or by accident henceforth.

Also, there have been postings with video/audio clips of Porsche engines exhibiting the IMS bearing death noise so there is no need to create any new clips.

I've even had the unpleasant experience of hearing this directly from a car that was on a lift in a dealership service bay. The car was in for the noise the engine was making and the brief (around a couple of minutes' time) the engine was running the techs confirmed the noise was from the IMS bearing area. The noise is not a healthy noise at all and while one might not know the IMS bearing is the source of such a noise anyone with a modicum of mechanical sympathy should know the engine's sick. Very sick.

Sincerely,

Macster.

Mabuhay

Can you link me? I've gone to Youtube and didn't find any (except the OP's). With me having 2 Porsches, I'm getting paranoid and am starting to hear things that may not necessarily be there.

Macster

When I posted that I was afraid someone would request a link.

I really have no notes on any links. I would have to search for some and I really can't do this at work and I have no 'net connection at home, so I would have to visit a local library to get 'net access away from the office.

If you want, do a google search using something like:

"porsche engine death rattle audio"

or some variation. Or you may be able to visit youtube and search there and with better/quicker results. I'm not a youtube member.

Or you can search here in the 986 and 996 forums. I'm sure in the last year or so there have been probably 6 or more threads started with someone posting an audio/video clip of a noisy engine. Some have been healthly, some just a bit sick and a couple on death's doorstep.

These engines are full of parts moving back and forth, up and down, around, and valves opening/closing, injectors opening and closing, spark plugs firing, and so on.

Also, the engine is located at a particularly good place to expose the driver to every bit of noise it makes. The engine air and engine compartment vents conduct sound from the engine compartment rather well.

In short these engines are a bit noisy and are located at the best spot to cause that noise to reach the driver's ears.

My advice is to take a deep breath, maybe two. The odds are very high your car's engine is just fine.

If you suspect the engine's sick, have it listened to by a professional who's experienced with these engines.

A professional mechanic can tell you very quickly if the noise is worth worrying about. If you listen and think you hear something out of the ordinary you're not going to do anything without a professional's opinion anyway so why not cut out the middle man?

Sincerely,

Macster.

Mabuhay

I actually did find a few videos in the 996 or other forums with people thinking it's the death rattle but ended up being the catalytic converters or something to do with the clutch. But of real interest here is that some "professional mechanics" also thought it was the death rattle, when it was not. Not saying they just wanted to work on the car. But honestly, they ALL sounded like "marbles in a can"!

Macster

The mechanics might offer the opinion the engine is exhibiting a death rattle. I've been the recipient of one or two of these diagnosis myself, well, not the death rattle kind, thankfully, but something less serious.

Often times they are like doctors, offering up a diagnosis of something soon to be terminal if not immediately taken care of (or diagnosed completely to know for sure what's going on) but then being able to deliver better news after a proper diagnosis is made.

The techs I watched guessed the engine noise was coming from the IMSB -- heck I made that guess the noise was clearly a sick engine noise -- but with the car in the air and the engine idling a mechanic's stethescope was used to clearly eliminate noisy/rattlely converters, loose plugs, bad coils, bad injectors, noisy heat shields, and so on. The noise was id'd as coming from the IMSB area of the engine. And it didn't take long. Just a minute or two.

Sincerely,

Macster.

mikstew

Macster the main reason for my post and tests depicted in it is that there are no other definitive videos or audio clips on the net of what a failed IMS bearing sounds like. Again, I speculate that this is due to the fact that an engine with ball bearings so worn that they literally rattle doesn't last long enough for the poor owner to record the engine's final moments.

On the bright side, if my engine dies in the next little while then we'll have definitive proof. D:

perfectlap

sorry to make an overtly obvious question, by why don't you just immediately take it to your Porsche specialist if you suspect symptoms of a pending engine failure? I can see wanting to look into something potentially non-catastropic via YouTube like a strange suspension noise. But this isn't that. It's only an hour of a mechanic's time while you could be pressing your luck (driving a car that shouldn't be driven).

logray

Definately +1.

You have a choice, and do you want to leave failure of a $15,000 engine (new) or $5000 (used/crap shoot) up to chance by diagnosis on an internet forum?