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Cat 955 engine knock


 
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Sharkbait24521
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Joined: 13 Aug 2017
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Location: Amherst, Virginia

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PostPosted: Tue Jan 15, 2019 9:15 am    Post subject: Cat 955 engine knock Reply to specific post Reply with quote

My Cat 955 K knocks at slow idle, as I bump the RPM up it will stop. Runs great at the higher RPM's Anyone care to comment on possible reasons? Timing is what comes to my mind, firing early, before piston TDC. I've only had the machine for a short while, just try not to idle it where it does it.
 
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Bob
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PostPosted: Tue Jan 15, 2019 10:12 am    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

I would first suspect an injector with low crack pressure or a bad tip.

Also, if you know how to do it safely, loosen one injector line at a time to narrow it down to which cylinder is knocking.

CAUTION!!!

"High pressure fluid can penetrate skin causing life-threatening injuries"!
 
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Nordic
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PostPosted: Tue Jan 15, 2019 2:32 pm    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

In the event that it is a bearing knock perhaps hook up a numeric oil pressure gauge to see what you have for oil pressure at idle in comparison to higher RPM.
 
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AJ.
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PostPosted: Tue Jan 15, 2019 3:52 pm    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

You need to find the source of that knock straight away,those engines are not very forgiving,see the engine is tight and the coupling between the engine and the torque is intact,like said crack each injector to find if there is a bad one,if ok remove the oil filter and examine it for metal flakes if you find any a bearing has picked up and it is best to not run it any more.
AJ
 
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Sharkbait24521
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PostPosted: Wed Jan 16, 2019 11:53 am    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

these replies scared me into contacting the cat mechanic. he says these machines are notorious for the coupling between the engine and torque
converter making the type noise I described. I will pull the oil filter and examine it carefully for metal bits. Didn't see any in old oil or
on filter when I changed the oil last time but will pay particular attention to it in the future.

Thanks for the advise.
 
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dpendzic
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Joined: 05 Mar 2009
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Location: long island NY and Hancock Ma

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PostPosted: Wed Jan 16, 2019 12:19 pm    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

you need to take the old filter and cut it open, say in half, to find any debris or metal flakes
 
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hector gemme
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PostPosted: Wed Jan 16, 2019 2:33 pm    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

I had 955k with the same probleme and it was the crankshaft was broken on last rear rod
 
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AJ.
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PostPosted: Thu Jan 17, 2019 1:39 am    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

Don't panic too much till you check the coupling,the couplings do fail if the engine is installed without lining it up properly when fitted,the run out between the torque and the engine has to be checked and adjusted,if the coupling is ok check the front mounting,the front mounting has a hub in the middle behind the crank pulley,inside that hub is a rubber inlay bonded to the inner and outside piece to separate the two metals if that wears away and the metal is sitting on metal you can get a knock sound from it at low rpm,if ok check the filter,you are looking for dandruff like flakes if a bearing is picking up but I don't think that is what is wrong cos if it was it would have knocked it out in a hour,what is coming from the exhaust,is the engine missing,if the worst happens that it is a bearing noise the main objective is save the shaft,it can be reground and have another life.machines!
AJ
 
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Sharkbait24521
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PostPosted: Thu Jan 17, 2019 12:12 pm    Post subject: Re: Cat 955 engine knock Reply to specific post Reply with quote

Thanks, will do.
 
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