3412 caterpillar

[maximi]

i have cat 3412 natural gas engine, last week when i shut down engine just when l shut down l can hear noise like metal grinding gear teeth, this l hear only on 200 rpm , when is cold engine nothing, so when l start and shut down immediatelly ln can hear this gear like few knocks on front side engine. i
l checked w pump, other pump and dont have clue what can it be, engine is runniong ok, compression ok, to take it apart is not quite option, l am wondering valve lifters or else, it can be hear on front of engine , but noice can be from rear comming, does anybody knows what can it be

 

[ivymike]

could be some odd vibrations from the last few firing events during shutdown?

 

[MikeHalloran]

Look for a broken or deteriorated motor mount.


Mike Halloran
Pembroke Pines, FL, USA

 

[catserveng]

Open up an oil filter element and look for metal debris, if there is an actual failure happening then it should show up there.

When was the last time you checked valve lash and bridge adjustments? The 3400 series of gas engines have had valve life issues, mainly shows up as excessive wear, valve face and seat on the exhaust valves, is accelerated by not doing valve and bridge adjustments at recommended service intervals. As the get worse in wear we had reports of "funny noises" shortly before dropping a valve. Look at the valve and bridge adjustment screws, all should be about the same, a noticable diffenrence could indicate an excessive wear problem. If you have an older service manual it will tell you that you only need to adjust the valve bridges after an overhaul THIS IS WRONG! Adjust bridges EVERYTIME before adjusting valve lash. Newer manuals should all be correct. Compression will usually test close to the other cylinders until wear gets really bad. Sometimes you can pick up indications of the problem by examining the spark plug. How do they all look?

What is the engine driving? I just had a gas engine genset that had a strange noise at startup and shutdown, turned out to be the generator bearing. Could be something in the driveline or driven equipment.

Hope that helps.

 

[maximi]

still noise on front distributor somwhere, we checked valves ok, oil ok, w pump ok, now we find a bit loose in one of front distributor gears , l dont know could this be problem , it seems when you try to concentrate on noise when shutting down that is getting from this part of engine , gear alike sound at wery emd of shutting like nock..nock...nooock, and we start again and when gets after few seconds to 200-300 rpm we shut down and noice at end is like that, so pump ok, valves ok, generator ok, filter element ok, oil ok, so this gear looks a bit looser a bit than others
l am from croatia and I do appreciatte all help from you guys, you are really good people and l thank you a lot, we have 4 3412 gensets working in parallelo on oil rig and all info from you is priceless
marko

 

[19Delta]

Does it sound like a tapping? We have a similiar engine and it does the same thing, it has alot of hours on it and i think it is normal.

 

[maximi]

finally we opened uo front distributor cover and we found some gears were grinding to each other, specially big idler from crankshaft to camshaft, so this could be problem becuase it sounds like teeth grinding at end of stopping, so we will replace them now, this gear if loose a bit could produce small vibrations on actuator gear so actuator lever is sometimes not steady