MACKS Posted August 18, 2008 Share Posted August 18, 2008 Hay guys,what should the oil pressure at Idle be on a 1996 350hp four valve motor be,the motor runs great nice and smooth with no blow by but with the truck wormed up the oil pressure drops to 18 lbs at idle and runs at 50 to 60 lbs when driving the truck,is this normal or is there a problem with the motor like crank and rod bearings or the oil pump.It has about 325,000 miles on it with no major work,Thanks for any Input. Quote Link to comment Share on other sites More sharing options...
HK Trucking Posted August 18, 2008 Share Posted August 18, 2008 Hay guys,what should the oil pressure at Idle be on a 1996 350hp four valve motor be,the motor runs great nice and smooth with no blow by but with the truck wormed up the oil pressure drops to 18 lbs at idle and runs at 50 to 60 lbs when driving the truck,is this normal or is there a problem with the motor like crank and rod bearings or the oil pump.It has about 325,000 miles on it with no major work,Thanks for any Input.All of the E7 engines that I had were all in that vicinity for idle oil pressure (15 - 20 psi)Most were around 50 - 60 psi @ 2100 RPM hot, with the exception of one E7 350 which was freshly overhauled and ran 60 - 70 psi @ 2100 RPM hot. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment Share on other sites More sharing options...
MACKS Posted August 18, 2008 Author Share Posted August 18, 2008 HK, Thanks for the quick come back. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted August 18, 2008 Share Posted August 18, 2008 Hay guys,what should the oil pressure at Idle be on a 1996 350hp four valve motor be,the motor runs great nice and smooth with no blow by but with the truck wormed up the oil pressure drops to 18 lbs at idle and runs at 50 to 60 lbs when driving the truck,is this normal or is there a problem with the motor like crank and rod bearings or the oil pump.It has about 325,000 miles on it with no major work,Thanks for any Input. most 2v and 4v macks I have driven idle @ 25-30 psi hot and 50-60psi @ 2100 Is the oil fresh or does it have high milage on it? any fuel in the oil? does the oil press rise quickly off idle (100 rpm off idle?)IMO 18 psi sounds a little low but nothing to be alarmed about as long as it holds steady. Quote Link to comment Share on other sites More sharing options...
MACKS Posted August 18, 2008 Author Share Posted August 18, 2008 Not sure how long the oil has been in the truck,the truck is for sale and the owner doesent know much about it,the truck came with a bussines he bought,it has been sitting for six months,the pressure jumps right up with a little rev. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted August 18, 2008 Share Posted August 18, 2008 I looked at my 1996 Mack tune up book and the spec for HOT idle is 10-30 psi and at HOT wide open is 34-64psi. Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted August 18, 2008 Share Posted August 18, 2008 I looked at my 1996 Mack tune up book and the spec for HOT idle is 10-30 psi and at HOT wide open is 34-64psi. Some times you will run into a 1700 rpm engine and it will have a different gear ratio on the oil pump drive gear so it will have enough pressure and then when you set them up to 2100 rpm they may have 100 psi. I have one here now that cares 90psi when hot but have not worried about it. It was a mix breed engine so it may have the wrong oil pump but it will be ok. 1 Quote glenn akers Link to comment Share on other sites More sharing options...
Dustan Houchin Posted January 26, 2021 Share Posted January 26, 2021 I have a 99 ch with a E7 mack motor was wondering how much oil pressure should be at ide and 2000 rpm its got 250 000 miles truck did sit for two years Quote Link to comment Share on other sites More sharing options...
Vmac3 Posted January 26, 2021 Share Posted January 26, 2021 15-20 psi at idle and 40-50 psi at 2100. These measurements are taken with the engine oil at normal operating temperatures. Anything lower than 40 psi then the engine brakes will not work effectively. V Quote Link to comment Share on other sites More sharing options...
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