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2000 460  It was rebuilt a year ago. Since the overhaul I been making oil. In 10,000 miles its up 3/8" above the mark. Before the overhaul it was fine ,I used to add between changes.  This has to be from the EUP o rings.?  correct.?  Is there any other place you can think of for fuel to get in the oil.?  I was thinking the plunger in the EUP pump but it didnt do it before. Just since the EUPs were out and put back in.  Here is the latest oil sample report, not good.  Thanks for your help.  Where should I start.

80-190803 (2).pdf

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Fuel transfer pump seal, EUP seal or fuel gallery drilling plug.

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I changed the fuel transfer pump no difference.  Whatever it is its getting worse. Last October the oil sample was 1% now almost a year later its 2.5% and the truck doesnt work from Jan til March. I run to a local asphalt plant. So basically 9 months it went from 1% to 2.5%.  I plan on changing the o rings on the EUP pumps this weekend. After that I have no clue..  Need help. Thanks

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Just now, wilbur said:

I changed the fuel transfer pump no difference.  Whatever it is its getting worse. Last October the oil sample was 1% now almost a year later its 2.5% and the truck doesnt work from Jan til March. I run to a local asphalt plant. So basically 9 months it went from 1% to 2.5%.  I plan on changing the o rings on the EUP pumps this weekend. After that I have no clue..  Need help. Thanks

In them 9 months I only put 40,000 miles on. 

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If the engine has a small plastic line to the head it can be injector o rings as well! Unlikely but a possiblity!

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Posted (edited)

Mack EUPs occasionally go chronic and leak no matter how You dress and install them(with standard o-rings). Mack made a special production of seals called the “Delta seal” kit. The lower ring is made of three individual parts that lay at complimentary angles. Get a 6 set and install them. I don’t believe Mack made the delta set a standard factory production install, but saw random cases where EUPs leaked and standard soft kits didn’t resolve the issue. Suspect maybe R&R of unit pumps eventually create little vertical scars on the wall of bores?

Edited by Mack Technician

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Posted (edited)

Wilbur, you also posted this thread on July 28, 2018. We had the same conversation, I don’t mind recapping.......but have you done anything on it since or is this the same leak.

Edited by Mack Technician
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Same leak getting worse last year oil sample was 1% now 2.5% diesel.   Now it started the stumble or miss. was reflashed and no better, Should I just replace all unit pumps.?  Is it possible for a EUP to leak fuel from the plunger or piston.?

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23 hours ago, Mack Technician said:

Mack EUPs occasionally go chronic and leak no matter how You dress and install them(with standard o-rings). Mack made a special production of seals called the “Delta seal” kit. The lower ring is made of three individual parts that lay at complimentary angles. Get a 6 set and install them. I don’t believe Mack made the delta set a standard factory production install, but saw random cases where EUPs leaked and standard soft kits didn’t resolve the issue. Suspect maybe R&R of unit pumps eventually create little vertical scars on the wall of bores?

 

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They were only taken out and put back in one time. They are original 700,000 miles. I figured I would change them and get rid of the stumble at the same time. Them delta kits are pretty pricey at 100 bucks each.  I cant see an o ring getting worse that s what led me to believe the plunger seal. Im also thinking a cracked head where the fuel return flows through. They are reman heads , not original. Already had trouble with one 3 days after the rebuild.

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Posted (edited)

WHAT!!! $100.00??? Hosed! Give me your part number and I’ll try to find a cheaper source. 

Edited by Mack Technician

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Wonder if "per set" comes with 6 sets....

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You can be right. This came from the mechanic through the parts guy, but it could be for 6.  I do know the regular o rings 2 for each pump is 180 bucks for the set ,12 o rings. That sounds really high for 12 o rings. 15 bucks each, They might be Viton but dont know

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If it fixes your problem is it worth the price?

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I ordered the pumps today from the Diesel Store and got mack to sell me the delta kits at 65.00  each. I will do this over the weekend and should know if it fixed it by the next weekend.

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These were Bosch remans rebuilt by bosch for 265

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I also have them the delta seals Mack sold me for 65 each.

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Put all EUPs in this weekend with the Delta seals. When #5  EUP came out it was in pieces. The clip that holds the plunger was off so was the spring retainer. Wonder if thats where my fuel was coming from.?

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Did the pump pop up when u unbolted it ? This will cause em to fly apart! Also I hope you are replacing the eup bolts they tend to break when reused !

Edited by fjh

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