Broke ma crank !

[Jamkar]

Hi guys, i'm a long time reader but this is my first post (i think), anyone able to tell me why me 90 model E6 350 4V would break the crank under number 2 mains. Done just under 1 million ks but was still going strong.

[Rob]

Hi guys, i'm a long time reader but this is my first post (i think), anyone able to tell me why me 90 model E6 350 4V would break the crank under number 2 mains. Done just under 1 million ks but was still going strong.

I've seen several crankshafts broken there, and more toward the rear on the E6 series of engine. Usually this is from driver's asking for more than the engine was designed to deliver,(a.k.a. heavy foot). No disrespect intended as I don't know the application. Most of the ones I've actually seen and worked on have be vocational type trucks such as dump, mixers, spreaders, etc. that are usually a lot of start and stop with heavy loading.

Age, fatigue, stress, and overtorque, and vibration, (as from a defective harmonic balancer) all play into the equation as to why this can happen. If the crankshaft suddenly snapped, and the engine did not effectively chew itself apart, you may be able to install a reman kit into the existing block with minimal work. I would however use a micrometer on everything including the main saddles, rod bearing journals, etc. Also use a new or reman harmonic balancer on the front of the engine upon reassembly.

Rob

[rhasler]

If the rod caps aren't aligned properly it will eat into the crankshaft.

[David]

Dave George ran a gear shop and wrecker service in upstate NY for decades. When ever he was ask why something broke he always said " Material fatique or driver abuse".

[Mike]

Dave George ran a gear shop and wrecker service in upstate NY for decades. When ever he was ask why something broke he always said " Material fatique or driver abuse".

That is still a good saying. True enough. I've heard the same over the years.

mike

[randyp]

Dave George ran a gear shop and wrecker service in upstate NY for decades. When ever he was ask why something broke he always said " Material fatique or driver abuse".

My dad always said,,"Well, I be damned, YOU tore the sumbitch up!" To hear him tell it, I must have been responsible for every breakdown in America in those days. randyp

[Mike]

My dad always said,,"Well, I be damned, YOU tore the sumbitch up!" To hear him tell it, I must have been responsible for every breakdown in America in those days. randyp

Yea, I can recall the same thing for me. My first car had a waterpump problem one morning and going to school. I hated to wake my dad but knew I had to do something. So I did and he said find a way to school the best way you can. So that meant walking. Lucky for me, cause it was a cold morning and spitting snow about half way down the street I found some friends heading out to school and got a ride with them. Yea randyp my dad thought if ya would leave things alone ya don't have as many problems that way......The ole saying was.....If it aint broke don't fix it. And don't be looking under the hood for something to fix.

mike

[220cummins]

Dave George ran a gear shop and wrecker service in upstate NY for decades. When ever he was ask why something broke he always said " Material fatique or driver abuse".

"running the rpms up to much when downshifting will do it. over revving."<-----driver abuse or a combo of that and material fatique with many miles or hours. Thats what i was told and taught when I first learned how to drive trucks.

[Lmackattack]

Can also be from Lugging to much. that was a known issue on the early maxidynes. but most cases it was the rear of the block that broke. Regardless things brake even with good care taken..

Trent

[theakerstwo]

It was used too much when it was new. Better get the main brg line bore checked. Mack engine work at low rpm in time will bend the block.I have pulled the caps down on many of them to find you cant get knew main brgs back in due to misalignment of the block.*55 cummins was bad to do that in the older engines.But the mack engine with the fuel cranked up will do it quicker.I had a freind that wanted me to do the bottom end. I new that this was a maxidyne and set hot so was slow about doing the brgs. I knew what would happen. Sure enough a couple years later i ended up pulling the engine and having it aligned.He could not beleive it cause it was ok till i pulled the pan.

[41chevy]

My dad always said,,"Well, I be damned, YOU tore the sumbitch up!" To hear him tell it, I must have been responsible for every breakdown in America in those days. randyp

Nope! I'm the one...my pop told me that 10000000's of times. Got a flat? why the "h" did you run over that nail for??