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95 e7-350 mechanical


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We have had this truck for 10+ years, and have never seen much boost pressure out of it.  It briefly hits 23 psi at 1700 rpms, but more than 50 rpms one way or the other and it drops to 20.  It gets where it's going, but I'm used to 25 psi from 1200 rpms to 2100 on our endt676 motors.  Is my '95 about right? Doesn't smoke, idles clean.  22k+ hours on it, 276k miles.  It's a concrete truck, lots of local operating time with minimal mileage.

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21 minutes ago, JoeH said:

We have had this truck for 10+ years, and have never seen much boost pressure out of it.  It briefly hits 23 psi at 1700 rpms, but more than 50 rpms one way or the other and it drops to 20.  It gets where it's going, but I'm used to 25 psi from 1200 rpms to 2100 on our endt676 motors.  Is my '95 about right? Doesn't smoke, idles clean.  22k+ hours on it, 276k miles.  It's a concrete truck, lots of local operating time with minimal mileage.

 350 mechanical! ! first check to see if the fuel shut off is going full off then check the the throttle lever for full stroke  ! All Good? yes !? then  Remove the 3/8 plastic line to the top of the fuel pump if u suck on that hose and it won't hold a vacuum  the diaphragm in that unit is holed needs replacing!

just three quick checks to start with!

Edited by fjh
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6 minutes ago, JoeH said:

Sorry that's in the topic title. E7-350 mechanical. 1995. Eaton 8ll.

check the above first easy stuff! keep us posted! Yup I edited my reaction I noticed the mechanical after the fact ! My bad! 

Edited by fjh
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23 hours ago, Dirtymilkman said:

Pressure check intake and cac. You are probably pushing boost out you cac. My 350 mechanical always hit 31 psi

I do hear a boost leak on occasion. Doesn't always do it, but sometimes there's a faint audible leak that builds with the turbo.  Is there a particular engine degree to close off enough valves that the pressure test won't leak through the valves?  Also, how do you close off the CAC turbo-side?

 

This truck also has a Cold Start bypass setup to bypass the CAC.  It has a small crossover pipe coming from between the turbo and CAC with an air operated butterfly valve, and another butterfly valve after the CAC.  This system effectively shuts off air flow through the CAC so it sucks in warm turbo air. Is it common for the cold start plumbing to generate a leak? 

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Posted (edited)

Boost leak would also explain why this truck runs hot on the pyro, even though it ever smokes...  Not hard to hit 1100°+ climbing a hill, even with 4 inch straight through muffler.

Edited by JoeH
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On 3/19/2022 at 8:17 PM, JoeH said:

Boost leak would also explain why this truck runs hot on the pyro, even though it ever smokes...  Not hard to hit 1100°+ climbing a hill, even with 4 inch straight through muffler.

yup! totally agree check the hose at the compressor  very common leak there! also have seen these bypass dodads stick!  Always by passing the charge air will cause high heat and low power! Most of the engines in our area here we disabled this unit it causes more trouble than its worth!

Edited by fjh
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Posted (edited)

Charge air cooler leaks like a sieve.  Bergeys put in a request to Mack to see if it's available, if it's not then what are my options?

RD688S chassis.

Edited by JoeH
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The guy near us closed up his radiator repair and shifted to selling welding supplies.  Nowadays radiators are plastic throw-aways, not much business in repair. I'll call him tomorrow and see if he's willing/able.

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1 hour ago, JoeH said:

The guy near us closed up his radiator repair and shifted to selling welding supplies.  Nowadays radiators are plastic throw-aways, not much business in repair. I'll call him tomorrow and see if he's willing/able.

A few years back a friend of mine had a rad shop for years and his dad did before him.But the cheapo rads was not repairable so he saw the light.He could build custom rad to fit any thing and his replacement cores was made from copper but it got were you could buy a new cheapo cheaper.My CH needed a rad and from mack i paid little over 800.00 for a new one then i open it up and its Aluminium with plastic tanks.

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glenn akers

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Bergeys has access to it, it'll be here in about a week. Anxious to see what 350hp feels like, this truck has always run a little hot on the pyro with no more than 25 psi boost.

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  • 2 weeks later...

Truck went from being a mutt tapping out barely at 20 psi of boost back to a bulldog at 30 psi of boost.  In 10 years of owning this truck we have never seen more than 25 psi out of it.

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10 minutes ago, JoeH said:

Truck went from being a mutt tapping out barely at 20 psi of boost back to a bulldog at 30 psi of boost.  In 10 years of owning this truck we have never seen more than 25 psi out of it.

What did you fix?    terry:MackLogo:

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The top "right" (passenger side) bolt must have dropped the rubbery washer out. That bolt wasn't holding that corner down well, but the bolt was seized: twisted off.  Had to drill and re-tap to take a 5/16 bolt instead of the metric junk that was in there.

 

Only got to do a 4 mile round trip test run empty today, looking forward to seeing how it runs loaded tomorrow! 

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