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ardakota

2001 mack 460 problem

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We have a 2001 mack ch 460  that we put a remack engine in ran great for the first couple thousand miles now when you put it under a hard pull it will begin to miss and when you stop from said hard pull and just let it idle you get a miss and a thump thump out the exhaust then a minute later it will clear itself up. I have never had a mack do that on me so this is new to me.  Thanks Dave

 

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Any smoke? Hard to say without hearing it. First thoughts are possibly bad unit pump, engine brake sticking.

Does it sounds like just a fuel miss, or a valve train miss? I know it can be hard to tell without a trained ear.

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It sounds like an exhaust valve is sticking it doesnt smoke just a thump thump thump sound out the exhaust along with a miss only happens after stopping from a hard pull it will still miss if you keep on going but stop it and let it go to idle then you hear the thump thump

 

 

 

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yes it has a jake it almost sounds as if its not turning off but coming out of the woods in a hard pull your not using it when it does it.

 

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I had one years ago that had a similar problem, it was the Jake, even turned off. We pulled the Jake housings off and ran it, problem disappeared.

In order to do that you would need shorter bolts obviously for the rockers. If it were me, that's the route I would take just to eliminate a Jake problem first.

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one would think you would see some smoke if it was fueling and the jake was opening a valve at the same time?

My only thought would be an intake valve hanging up!

Edited by fjh

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a real long shot  rocker lever shaft not getting oil and partialy seizeing a rocker arm

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Yeah by the sound of ardakota's description, it sure sounds like a valve train issue. Might be difficult to isolate which cylinder if it only does it for a brief time at idle.

 

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I have had an intake valve problem when the cam was going out in the previous engine and kept breaking that post that holds the rocker and it always thumped back through the breather bUT I'm like you guys I think it's got to be valve train related. Maybe it's time mack look at their motor it shouldn't be doing this with so few miles.

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Yup get on it ! it should have a warrenty period and time is ticking!

Was it a long block or short block? long you should be good to go! short not so much Ive seen cracked rocker shafts cause the jake to come on how ever if they are your shafts and it is the problem you pay! Let us know how this turns out!

Edited by fjh

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Not to get off track but I put a basic in last year, fired it up, thump thump instantly. One of the cam rollers had a flat spot. That's when I learned Mack doesn't replace all of the lifters, they just inspect and reuse. No telling what your gonna get anymore I guess.

Dakota, I don't know what kind of relationship you have with your dealer, but there are plenty that will do everything they can to pin it on you somehow. I'm with fjh, maybe let them take a look. 

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Yeah it was a full remark engine long block

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Ok good, at least they can't pin a rocker problem on you. So you just bolted your Jake onto it then and readjusted valves?

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