Straydog954 Posted January 18 Share Posted January 18 I have an em7-300 mechanical in a dump truck that has 470k miles and high hours 28k or more. It seems to start fairly easy in cold weather and runs nice but uses a lot of oil. Should I assume that it’s time for a rebuild? What is the easiest way for me to tell? Would taking off the heads and looking at the cylinders be a good start or is this wasting time because of the inevitable? Quote Link to comment Share on other sites More sharing options...
MACKS Posted January 18 Share Posted January 18 How’s the oil pressure,does it have excessive blow by? 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted January 18 Share Posted January 18 I have seen these go way over 30 thousand hours! If it ain't broke don't fix it! Comparatively speaking oil is cheap! 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 18 Share Posted January 18 Yeah, I'm leaning towards FJH's side and checking blow by is good to do. You didn't mention blue smoke, or leaks, or even how much oil you are adding and the time frame.. Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 18 Author Share Posted January 18 Oh sorry I should have added more. It has a fair amount of blow by but is not puffing hard like a freight train. From what I recall oil pressure is around 15 at idle and 60 on the high end. Truck was bought used and I found a service record at Mack that truck had rods and mains done at appx 180k due to a strange noise. I see a remack sticker on one of the heads and assume maybe both have been replaced judging by the paint looking the same. I found the serial number on the block and it matches the serial number on build sheet from Mack museum so original block. Sometimes I will see blue exhaust at idle but most times it’s clear. Sometimes it will use a gallon of oil a day other times I can make several hauls and oil level does not move. Slight leak around pan, no dripping leaks. Took off turbo (reman) and took it to a shop they said it was tight and not the problem. I did notice exhaust ports seemed damp inside. On a few occasions while idling the engine was puking oil out between the turbo and exhaust pipe. Wonder if it has worn rings and liners? I really appreciate all of your help. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 18 Share Posted January 18 It sounds like you did your homework :). 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted January 18 Share Posted January 18 Teck Tip ! DON'T Idle ! Too much idle Not enough work makes Mack a dull boy! 🤣 2 Quote Link to comment Share on other sites More sharing options...
Mark T Posted January 18 Share Posted January 18 Might sound silly, but maybe a good tune up with some new injectors ? Some good quality engine oil. Might slow the aging process a little. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 18 Share Posted January 18 have you considered replacing the valve seals? you can do it with the heads on the engine.. Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 18 Author Share Posted January 18 These are the ideas that I’m looking for. All I really know how to do is change fluids and filters etc. I have self diagnosed all small problems with this truck by replies from guys like you on this website. Have never had to go to the dealer yet lol. It would be nice to figure out why I’m using oil before I just drop it off at an engine rebuild shop. I’ve read worn valve seals or valve guides as a possibility also. Maybe that would be the easiest thing to go after first? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 18 Share Posted January 18 The dealership, is going to try to sell a ''Basic'' to you.. I wouldnt expect them to have a knowledgeable re-builder in house. also, if its a Mack dealer, they are going to tell you that the re-man center doesnt have any E-7's and they want yours to re-build, and it will be 6 months till it's done. I dont know what is available to you as far as skilled shops, so forgive me if i'm out to lunch.. Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 18 Author Share Posted January 18 1 hour ago, Mark T said: Might sound silly, but maybe a good tune up with some new injectors ? Some good quality engine oil. Might slow the aging process a little. Yah I’ve never had anybody touch anything on the engine or had anything done to the injectors and I’ve put 20k miles on it. I use Shell Rotella oil. It’s always used the same amount of oil since I’ve run it. Maybe a valve adjustment, injectors would be good. 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted January 19 Share Posted January 19 18 hours ago, Straydog954 said: Yah I’ve never had anybody touch anything on the engine or had anything done to the injectors and I’ve put 20k miles on it. I use Shell Rotella oil. It’s always used the same amount of oil since I’ve run it. Maybe a valve adjustment, injectors would be good. In my mind its all in what you intend to do with it! If you intend on keeping it and its a daily work horse then you could spend the bucks! How ever how far does one go with it! ? You can get into this for 30000 K and what is the unit worth? If your mechanically minded You could pull the heads pop out the the pistons re ring it! Economically and pop it back together! that would likely deal with the oil consumption blow by issue ! how ever you still got to consider how long will the liners last till they leak etc. I could go on and on! Its a catch 22! How much will insurance pay you if the truck gets wrote off? if it costs 10 bucks in oil day after day of running add it up! And as Joe mention Skilled labor these days NOT The greatest! 1 1 Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 19 Author Share Posted January 19 5 hours ago, fjh said: In my mind its all in what you intend to do with it! If you intend on keeping it and its a daily work horse then you could spend the bucks! How ever how far does one go with it! ? You can get into this for 30000 K and what is the unit worth? If your mechanically minded You could pull the heads pop out the the pistons re ring it! Economically and pop it back together! that would likely deal with the oil consumption blow by issue ! how ever you still got to consider how long will the liners last till they leak etc. I could go on and on! Its a catch 22! How much will insurance pay you if the truck gets wrote off? if it costs 10 bucks in oil day after day of running add it up! And as Joe mention Skilled labor these days NOT The greatest! I hear yah brah. I hate to put 30k into a truck I paid 20k for and put 3-5,000 miles on per year. It’s a part time haul truck. I do like the ruggedness, simplicity and reliability of this truck you can’t beat it. If it was a daily workhorse it would be a no brainer like you said. If I have it ringed, how do I tell if the liners are still good and not worn out? Is there a measurement spec or how do you tell? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 19 Share Posted January 19 straydog... did you forget to post something?? jojo Quote Link to comment Share on other sites More sharing options...
JoeH Posted January 19 Share Posted January 19 How's the frame on the truck? If the frame is rust jacking bad and doesn't have much life then is it worth the fuss other than dumping oil in? I have a 1995 e7-350, 24k hours. I have noticed on my truck that if I shut it off and give it 5 minutes it'll be a gallon low. If I come back in the AM it'll be at full. Sometimes the truck will "load up" on oil while idling and blow a smelly blue haze, but most of the time it runs clean. Mine also developed some fatigue cracks in the oil pan at the corners. New pan was $2,000, came with pin holes for gasket tabs to push through. Of course the dealer gave me the old style cork gasket, and i didnt know about the rubber gasket so I welded the holes shut... What's your engine idle rpm? Over time the setting can dip, and then you aren't idling fast enough to keep the rings sealed well enough on combustion. Quote Link to comment Share on other sites More sharing options...
JoeH Posted January 19 Share Posted January 19 14 minutes ago, Straydog954 said: Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 20 Author Share Posted January 20 15 minutes ago, Joey Mack said: straydog... did you forget to post something?? jojo Not sure. I think I hit the quote button twice when I replied to fjh. He said maybe I could have new rings put in the engine. If I have that done how do I check liner wear? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 20 Share Posted January 20 (edited) with a bore mic.. pull the wrist pins and inspect the bushings, if they are good, just hone the liners and re-ring your pistons and put them back in.. all of what he (fjh) said about cost and usage is real time thinking.. he's right.. jojo Edited January 20 by Joey Mack More content needed Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 20 Author Share Posted January 20 15 minutes ago, JoeH said: How's the frame on the truck? If the frame is rust jacking bad and doesn't have much life then is it worth the fuss other than dumping oil in? I have a 1995 e7-350, 24k hours. I have noticed on my truck that if I shut it off and give it 5 minutes it'll be a gallon low. If I come back in the AM it'll be at full. Sometimes the truck will "load up" on oil while idling and blow a smelly blue haze, but most of the time it runs clean. Mine also developed some fatigue cracks in the oil pan at the corners. New pan was $2,000, came with pin holes for gasket tabs to push through. Of course the dealer gave me the old style cork gasket, and i didnt know about the rubber gasket so I welded the holes shut... What's your engine idle rpm? Over time the setting can dip, and then you aren't idling fast enough to keep the rings sealed well enough on combustion. The frame is decent not a lot of jacking, just a little bit in the rear frame area. It was a southern truck originally then spent some time in the mid west where I bought it out of Nebraska. I only run it in the summer as a part time gravel hauler. My truck has also loaded up while idling to the point where it was dripping out of the turbo but then it corrects itself. I’m thinking my truck idles around 600 rpm if im thinking correctly. Quote Link to comment Share on other sites More sharing options...
Straydog954 Posted January 20 Author Share Posted January 20 11 minutes ago, Joey Mack said: with a bore mic.. just hone the liners and re-ring your pistons and put them back in.. all of what he (fjh) said about cost and usage is real time thinking.. he's right.. jojo I know you guys are right. That’s why it hasn’t been dropped off at an engine shop somewhere lol. I just need to find a competent person to dig into it. If the heads come off, what spec. am I looking for with the bore mic any idea? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 20 Share Posted January 20 just look at cross hatching.. if there is some left, just hone them and GO!.. the new rings will make up the difference. it will run fine.. you may have to trim the carbon ridge at the top of the liner, but that is common for liner re-use.. before you pull the heads, come back for more advice.. 1 Quote Link to comment Share on other sites More sharing options...
JoeH Posted January 20 Share Posted January 20 1 hour ago, Straydog954 said: The frame is decent not a lot of jacking, just a little bit in the rear frame area. It was a southern truck originally then spent some time in the mid west where I bought it out of Nebraska. I only run it in the summer as a part time gravel hauler. My truck has also loaded up while idling to the point where it was dripping out of the turbo but then it corrects itself. I’m thinking my truck idles around 600 rpm if im thinking correctly. Up the idle speed to 650 rpms where it belongs. Should just be a screw stopper on the fuel pump that the throttle lever stops against. Micro switch for the engine brake may block your view of it. 1 Quote Link to comment Share on other sites More sharing options...
BOBWhite Posted January 20 Share Posted January 20 If the hours and miles are correct then that means this truck has been doing about 17 MPH its whole life, so probably lots of idle. For reference 28k hours is about 3.5 years of continuous running! Blows my mind! About 8-12k is all we get out of our John Deere engines before needing to be gone though. These Mack E6/E7s are still some of the best engines ever built. Keep the 3406s and N14s I'd take a Mack! Quote Link to comment Share on other sites More sharing options...
67RModel Posted January 20 Share Posted January 20 A friend of mine had a large fleet of Mack roll off trucks. E7s and ASET engines. 35,000+/- hours was routine before overhaul. His fleet average mph was around 25 mph. I think most vocational trucks are around that 25mph number unless its some type of specialty truck that does a lot of stationary pto work like a stone slinger or volumetric concrete mixer. I would expect an over the road freight truck to be in the mid to high 40s for overall mph..... Quote Link to comment Share on other sites More sharing options...
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