boogaman Posted February 28, 2015 Share Posted February 28, 2015 Just bought this truck RD 688S 93 model dump with '90 model e7-350 I suppose because of the tag on the covers. Truck runs great good oil pressure well taken care of. The oil looks like it's brand new literally. We have hauled several loads with it in the last few days , all of a sudden today with a load on it starts knocking not all the time but off and on pretty loud. It still has good oil pressure ,maybe a little slower to start and seems to be more towards the top end. Oil level is still good and clean. No smoke. Can anybody give me some advice on what this might be? Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted February 28, 2015 Share Posted February 28, 2015 Yes shut it down and get into some shop for repairs. Quote glenn akers Link to comment Share on other sites More sharing options...
j hancock Posted February 28, 2015 Share Posted February 28, 2015 Do an oil analysis. Any quality diesel shop or parts store can get you a kit.Somebody may have done an oil change to hide something. Quote JimIt doesn't cost anything to pay attention. Link to comment Share on other sites More sharing options...
ranchhopper Posted February 28, 2015 Share Posted February 28, 2015 Could be a bad injector giving you a fuel knock too. Quote Link to comment Share on other sites More sharing options...
boogaman Posted February 28, 2015 Author Share Posted February 28, 2015 Thanks for the reply folks. Yeah we shut it down and wreckered it to the shop. They may have changed the oil to hide something but it has stayed clean all the while. I'll let you know what happens today after some checking. Really appreciate yall. This is a great site I've never posted on here but have always got a lot of useful info. Quote Link to comment Share on other sites More sharing options...
farmer52 Posted February 28, 2015 Share Posted February 28, 2015 The oil can still look "clean" and be contaminated with metals and or fuel. Good idea to have the oil analyzed. Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment Share on other sites More sharing options...
b61mack Posted February 28, 2015 Share Posted February 28, 2015 I have rebuilt a few E6s that had a slight knock turned out to be small pieces of the rings on top of pistons. Quote Link to comment Share on other sites More sharing options...
boogaman Posted March 1, 2015 Author Share Posted March 1, 2015 Mechanic listened to it today said he was pretty sure it was #4 piston maybe wrist pin or cap. Gonna get the pan off Monday and inspect. Least their givin rain this week. Quote Link to comment Share on other sites More sharing options...
boogaman Posted March 12, 2015 Author Share Posted March 12, 2015 Well it was a spun rod bearing 😞 Quote Link to comment Share on other sites More sharing options...
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