Weird engine noise in a 3.2
 

While at the track my car made a noise like I blew my transmission, like loose gear noise, that’s the best description I can come up with. After further investigation here are the symptoms:

Idling, the motor sounds normal
When it’s revved past 2500 rpm the noise comes back
It sounds like a loose spinning gear.
I have eliminated the alternator.
I think the oil pressure is a little low and fluctuation.

My guesses are:
1) Oil pump
2) Something with the intermediate shaft
3) Flywheel came loose
4) Main bearing

Would anyone like to guess???

The engine is a 3.2 with 130,000 miles. I rebuilt it 10,000 mi ago because of a failed rod bearing. 95% of the miles after the rebuild are track miles.

Thanks,

Tim

Is the noise only present in certain gears, or all gears? Or are you in neutral and hearing these noises.

The noise is when the rpms are over 2000 in any gear or neutral clutch in or out. I drained the oil and there is nothing on the drain plug so that eliminates main bearing I think.


Tim

This could be a weird one, but I had a CAT fail on a jeep and it sounded like a rattling ball bearings. Sounded normal at idle.
See if the sound is coming from that area.

Symptoms sound similar to a sound I have been trying to track down. The difference is, my sounds disappear as soon as the clutch is depressed or the car is placed in neutral. Happens on acceleration and deceleration. I've eliminated the CV joints as the culprit by replacing them. I am suspecting the bearings in the differential. Not exactly a DIY repair job.
I have no CAT by the way.
I'll be anxious to hear if your problem is solved. It might shed some light on the source of my issue.

-Brad

I'm quite sure I have the same noise you describe. Comes on around 2000 rpm and fades away after 3000-3200 rpm. Sounds like spinning gear chatter, as you described. Sound exists whether car is in gear or not, exists with clutch engaged or not, exists when moving or not. So I ruled out the transmission

I can also confirm it's not the alt., as I just replaced mine and it actually seems to have added a whirring noise. Chatter noise remains.

It's not the chain tensioners either. That's not to say it couldn't be the idler arms & sprockets, or anything else associated with the timing chain system.

I would agree with goat's cat. conv. suggestion as a possibility, because my buddy Mark's Jeep Grand Cherokee did the same thing. My 911 has no cat., so the problem must be something else.

I have no cat so that’s out. I'm going to cut the filter and see if anything turns up. I would hate to tear the motor apart and not find anything.

Thanks,

Tim

My G50 doesn’t make any noticeable noise. But, it’s repetition is to be nosier than the 915 or 901. Have the upgrades been done on the transmission? LSD?

Well, my first thought was the chains or something to do with them, but that's just a guess.

Update: I finally had some time last night and dropped the motor. Found the problem immediately!! Snapped crank!! The flywheel end was loose so I assume it’s cracked in the #6 crank journal and the bearing is holding the thing together.

Tim

Jeez....snapped crank? How could that happned? Overheated bearing?

Please post pictures...

Wow! I'm surprised the thing didn't grenade on you. Tim, perhaps it's time for some upgrades. :)

Kevin, Do you have a sinking feeling right about now?

Does anyone know where I can get a used 3.2 crankshaft?

Thanks

Tim

Tim,
The 911 classified section lists this member as having a crank for sale:

http://forums.pelicanparts.com/showthread.php?s=&threadid=159669&highlight=cranks haft

If no longer available then place a WTB (Wanted To Buy) ad in the same section. You'll most likely get offers in short notice.

Couldn't you just fix it with JB Weld?:D

Nah. I just keep driving it. My buddy Mark's car (86 Carrera) seems to make the same sound. Maybe it's nothing.........:confused:

If it breaks, I park it for awhile 'til I can afford to fix it. I'm more concerned about the stiff clutch and weird noises my Laser has been making lately................ :D

JB Weld. :p Yeah. That's a good one. That stuff has become the duct tape of adhesives nowadays. In all seriousness, that stuff never works for me. Just tried to fix a broken headlight piece on my Laser with that stuff. Didn't hold worth a darn.

Will I need to regrind the journals after the JB weld or can I just drive it?

Tim

I finally had time to tear the motor down last night. I don’t think JB weld is going to work.http://forums.pelicanparts.com/uploa...1087391892.jpg

Damn! I have never seen a crank break there. Any idea what caused it? I can't help but think it is somehow related to a possible stress fracture starting at the oil feed hole.

Now that is a scary picture - damn - anything happen before that? Missed shift - back off a cliff? rearended by a Escalade?

It happened on a downshift at Watkins glen going into the bus stop. I think the cause was the crank was repaired. I had it ground and that must have introduced an initiation point for the crack.

Tim

I don't understand what I'm looking at in that picture since I've never been inside an engine. Someone want to describe it?

BTW:
"I'm quite sure I have the same noise you describe. Comes on around 2000 rpm and fades away after 3000-3200 rpm. Sounds like spinning gear chatter, as you described"

I have the same noise. Comes and goes. For long, I thought it was my chain, and actually put new tensioners in it. I STILL here it from time to time. It sounds like a grinding/spinning something at moderate RPMS (like 2000-3000) and it comes and it goes. In fact, it still sounds like the chains. My oil pressure blows chunks. It never gets above 3, and it's at zero when the car is 2000 rpms. It's always a few integers behind the RPM value (5,000 rpms = 2.5 to 3 oil pressure measure).
Been like this for years.

Kurt

Does the sound change with engine load or just rpm.

That is a picture of the flywheel end of the crankshaft. The crack starts at the #6 rod journal and goes into the main bearing journal.

Tim

No, I hear it at low idle. Maybe it is the chains dragging on the ramps or something?
Okay, so how does the flywheel mount to that thing? Sorry, i've never seen a flywheel either :) I know it bolts on...that's about it.

The crankshaft in the helicopter was ground to .010" under, and oversized bearings were used. Legal fix, by the way.

Well, after 30 hours, the crankshaft let go in three pieces. :eek: Yes, I was flying (1500' over Redondo Beach). Fortunately, training paid off and I was able to do a safe emergency landing.

The moral to the story: I will NEVER use a repaired/ground crankshaft in any vehicle I own...in the air or on the ground!

Tim

Did you ever get the crank magnafluxed before or after the grind? How much total grind?

Lot of undersized crankshafts out there in use that don't fail.

At least you tore it down before it had a chance to destroy the whole engine. Smart move on your part. A great lesson for all to remember.

Thanks

Before the repair I had it magnafluxed and checked for straightness. The shop that repaired it also magnafluxed it. The crank was ground then hard chromed and ground to standard. Something in this process compromised the integrity of the crank, I think.?

Tim