Broken Crankshaft!?!

Reply Subscribe

Thread Tools

Search this Thread

Apr 30, 2013 | 07:42 PM

Trailerboy

Thread Starter

Cruising

Joined: Nov 2010

Posts: 13

Likes: 0

From: Portland Oregon

Broken Crankshaft!?!

My 99 C5 m-6 Z-51 coupe with 77,000 miles developed a strange knock when turning off and on a few weeks ago. Drove fine, smooth, no low oil pressure, no hi temps. I took off the serpentine belt, and the noise was still there. I took it to my mechanic, and he called me when it was in the air to take a look. There is some oil coming out of the rear main, but you can grab the flywheel and rotate it both directions about a half an inch without any resistance. Flywheel to crank bolts are tight. He said that the only thing that would cause that is a broken crank in an angled fashion at the rear hub. I've never heard of a broken crank on a bone stock LS1. Anyone else?

Apr 30, 2013 | 09:57 PM

feeder82

Safety Car

Joined: Mar 2005

Posts: 3,757

Likes: 1,215

From: Wisconsin

find a different mechanic i dont think u would be able to drive it with a broken crank

Last edited by feeder82; Apr 30, 2013 at 09:59 PM.

Apr 30, 2013 | 11:16 PM

Jay-rod

Pro

Joined: Jan 2005

Posts: 712

Likes: 0

Hi,
did you have any detonation issues,or any other reason to have bad harmonics(vibrations) in the engine/drive line?

I broke a crank in a 302 ford (built)not too long ago and I never heard of a crank breaking either. It did run but knocked very badly. It was from the balancer and the essentric slipped and vibrated the crank apart at the counterweight.Not an LS1 but I imagine it could happen given the proper variables.

Apr 30, 2013 | 11:17 PM

Mike94ZLT1

Le Mans Master

Joined: Jun 2002

Posts: 8,352

Likes: 103

From: In the pit, trying to love someone.

I've never heard of it but that doesn't mean it can't happen. Does he have the drivetrain out? How do you know the flywheel bolts are tight?

May 1, 2013 | 12:17 AM

T-TOP TOM

Pro

Joined: Oct 2001

Posts: 668

Likes: 26

From: Wadsworth Ohio

Many years ago a car came to my father's repair garage that had the crank broken on an angle. It ran but did have a knock in it when you backed off on the throttle or shutting it off.

May 1, 2013 | 04:42 AM

vettenuts

Team Owner

Joined: Mar 1999

Posts: 22,025

Likes: 192

From: At the beach in little Rhody

One of my co-workers had this happen to a Mercedes a number of years back. I believe the car still ran with it so I think the potential is there for any car and as stated by Jay-rod you may have some conditions that were the root cause. The harmonic damper condition or if aftermarket manufacturer, may be a major contributor. I would check that as well.

May 1, 2013 | 08:32 AM

bracketshark

Burning Brakes

Joined: Oct 2004

Posts: 985

Likes: 23

From: Florence SC

I doubt its broke, it probably needs a new timing chain though. That is about how much slop is in a stock timing chain when checked that far out from the center of the crank. Have him check the end play on the flywheel, if its broke it will move in and out since the thrust bearing is on the middle journal of the block. If the timing chain is a issue (it was for me), consider a Roll Master timing set, it tightened mine right up.