bumpytruck Posted September 14, 2009 Share Posted September 14, 2009 I have a few questions. First I have a 1980 DM Dump truck. It has the original motor however I am uncertain as to what has been done to it.I believe it has approx. 800,000 miles on it. It has blow by pretty bad and the oil pressuer is starting to flucuate a bit. I want to make thru my season. (nov)I would than like to do a rebuild on the motor.I have done many gasoline motors in my years but have never tackled a diesel of any kind.I just put a new turbo on this motor in july.I can pull the motor if need be but would perfer doing a in frame.Any advice would be greatly appreciated. Can someone advise were to purchase a manual for rebuilding this motor.What special tools are required.(Mack Specific) Quote Link to comment Share on other sites More sharing options...
Bollweevil Posted September 14, 2009 Share Posted September 14, 2009 If you are havig issues with oil pressure, now is the time to deal with it. Crankshaft bearings are a lot cheaper than a crankshaft and a set of bearings. If the oil pressure increases when you let off the throttle, the mains are probably about gone. Don't wait too long. Manuals from Mach are pricey, I have seen some on ebay. Quote Link to comment Share on other sites More sharing options...
bumpytruck Posted September 14, 2009 Author Share Posted September 14, 2009 I dont use the truck alot nor everyday,I use it for my concrete business.I did see some manuals on ebay but not the correct ones,I just thought there might be another place besides a Mack dealer.The oil does not go up when the rpm goes down.I lose about 10 psi when its warmed up. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted September 14, 2009 Share Posted September 14, 2009 Lousing oil press when its warm is normal. 60-90 psi cold is good / 30psi idle is good. if you cant get the oil press up over 40 after its warm it may be worn out. On the other hand I have seen some trucks run around 25psi at hot idle and then as soon as you give it 100RPM it shoots up to 70psi.What is your hot idle and cold start psi?I think my truck needs bearings soon because it is only 60 psi cold and 40 going down the road. I can hit 45PSI if im @2100 but I still think its too low of oil press. Quote Link to comment Share on other sites More sharing options...
bumpytruck Posted September 14, 2009 Author Share Posted September 14, 2009 It was about 60 cold and 30 hot and back up to 50-60 going down the road and it has dropped to about 25 at idle and it goes up to 40-50 going down the road.But it has bad blow by. Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted September 15, 2009 Share Posted September 15, 2009 If you ant a diesel mechanic then at least get a mechanic to help. When you make a mastake in this engine it can mean a new engine some times. I can think of a lot of things a manual can not learn you on a one time over haul.I would try to find a mack dealer mechanic to do it on the side if you have a place and air for him to work.I would exspect it would cost you maybe 750 or 1000.00 for a side job but may be worth it in down time and the cost of a mishap. Quote glenn akers Link to comment Share on other sites More sharing options...
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