Caterpillar GC40K-STR:
GM 4.3L ENGINE VIBRATION..THEN LOUD CLUNK.. NOW NORMAL

Hello, we have a CAT GC40K-STR with Lp gas powered GM 4.3L engine. this morning the engine began vibrating pretty bad. then heard a "clunk"..now engine is not vibrating. checked u -joints and harmonic balancer pulley but no obvious damage. engine starts and runs..but i'm wondering what could have caused this?

thanks
Jay
  • Posted 12 Mar 2015 06:22
  • Discussion started by glenn_levit7
  • Texas, United States
Montacargas, Tequila y Limon!
Showing items 1 - 4 of 4 results.
yeah at this point if you did not find anything loose, or damage to anything and it stopped vibrating it's time to let it run and see if anything else shows up later on. Hopefully if it does it wont be serious.
  • Posted 17 Mar 2015 11:15
  • Modified 17 Mar 2015 11:15 by poster
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
hello, followed suggestions and checked out the hyd pump and pulley, also checked on flex plate and all looks ok. also checked ignition wires and they are ok. will replace aftermarket wires with OEM anyway but for now engine is working well. one thing operator told me was that when it started shaking or vibrating he gave it more gas and the vibration went away. i was not able to duplicate vibration while performing troubleshooting and following suggestions. for now, since the units is running fine i will wait for it to start acting up again unless somebody has another suggestion.
  • Posted 17 Mar 2015 08:35
  • Reply by glenn_levit7
  • Texas, United States
Montacargas, Tequila y Limon!
if you found nothing between the engine and hyd pump area wrong i would pull the cover off the top of the flywheel housing and check the flex plate on the torque converter and make sure it is ok, may have a broken flex plate. (this is common on these units but is usually accompanied by a noise when running coming from the flex plate rattling)

if nothing is wrong there it might of been a cylinder not firing correctly and engine missing causing the vibration, then something let the cylinder start firing and that might of been the clunk you heard, maybe a small backfire or something... when all cylinders started firing again, it smoothed out.
Bad wires can cause this.
  • Posted 12 Mar 2015 22:09
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
pulley that is between the crankshaft and the hydraulic pump, on the pump side.
  • Posted 12 Mar 2015 11:40
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"

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