Reduced engine power - Cummins 6BT

Discussion in 'General Chit Chat' started by LJRuddy, Mar 30, 2012.

  1. LJRuddy

    LJRuddy Pop lock n drop

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    I've got a 97 Freightliner FL70 with a Cummins 6BT in it. lately I have noticed that the turbo will not start to boost until about 2000rpm and it won't reach peak boost until I am about 100rpm past my shift point (2600). The engine has something like 17,000 hours on it but the heads and turbo were rebuilt about 5,000 hours ago. They were redone because the truck was parked in an underground storage cave and shit started to rust.

    This problem wasnt a huge issue until lately when the weather got warmer. And now that the engine fan comes on more often and for longer periods of time, the truck is really a dog in the city (where I do 80% of my driving). Its so bad that I am getting passed by fully loaded dump trucks from a dig.

    I gotta go in to work tomorrow to fix an oil leak and get the A/C working again so while I'm there, I figured I'd see if anyone here knows what I should look for to help solve this problem.

    :wave:
     
    Last edited: Mar 30, 2012
  2. SHOtime2511

    SHOtime2511 CGP

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    boost leak?
     
  3. jc2001s

    jc2001s SHO Member

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    CAC would be my bet. If you have a CAC tester it would be great time to test it out, otherwise if you don't you can make one, but it might be more practical to just take it to a shop that can pressure test the CAC. Pretty common thing to go out on those ones. Also check all the boots, make sure you have constant torque clamps on all the CAC/Turbo boots.

    Other than that I doubt you have Jake's but if that could cause this problem too.

    I will be at work tomorrow (I work for a Freightliner dealer in parts), shoot me your last 6 of your VIN so I have a better idea on how your truck is set up.
     
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  4. LJRuddy

    LJRuddy Pop lock n drop

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    The cheapest heavy truck service shop around charged north of 250/hr to work on these damn things and the boss and I really don'y enjoy taking our trucks there for that reason. How do you make a CAC tester? I'm a bit of a noob when it comes to diesel stuff. I'm heading off to get my hair cut and then going to the shop to do work so I'll grab the last 6 and PM them to ya. :salute:


    EDIT: I don't think its a boost leak issue as I can hear the turbo spooling. Previously when the truck was working, the turbo spool would almost disappear when it reached peak boost. Now, it never goes away and from what I can tell, its only boosting maybe 85% of what it 'sounds' like it should be doing. I need to get a damn boost gauge and see what is actually going on though.
     
    Last edited: Mar 31, 2012
  5. jc2001s

    jc2001s SHO Member

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    To make a CAC tester, basically you want to plug both ends of CAC (air tight) and have a way to have an air gauge on it and add pressure. You pressurize the CAC up 30 psi and check the air gauge to see if it has leaked down at all, rule of thumb is if it leaks over 5 lbs over 30 seconds its bad.

    Also a this would be considered a boost leak, but you probably wouldn't hear it as a leak. And because you are not getting pressurized air into the engine (esp if the CAC is leaking you won't get very cold air into it) your engine will run hotter, and you should be losing fuel mileage.

    HOLY CRAP 250/hr we are at 128/hr and I thought that was steep...Any mom and pop shop that works on large diesels will have a CAC tester or have an improvised one, like one that you could make.
     
    Last edited: Mar 31, 2012
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  6. Denny

    Denny Taurus Homeland

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    Good lord! Are you sure it wasn't $250 for the labor for the job? I deal with shops across the country and the highest I've run into are Cat shops in NY or NJ at $140/hour.
     
  7. LJRuddy

    LJRuddy Pop lock n drop

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    Lets put it this way... KC Freightliner charged us about 1800 bucks for a front end alignment and to diagnose and fix a bad misfire on our C6500. The misfire turned out to be a loose connection for the engine harness and they didn't even bother to straighten the steering wheel. The same shop charged us 40 bucks to put in a turn signal bulb during our DOT inspection. The other companies around are not much cheaper.
     
  8. jc2001s

    jc2001s SHO Member

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    Holy crack! No seriously are they on crack?
     
  9. LJRuddy

    LJRuddy Pop lock n drop

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    Thats why we're starting to do our own work on the trucks...

    I got your PM btw but I got dragged out to an install site so I wasn't able to work on the truck today... Kinda glad. Its 87 and humid and I really don't feel like sweating my balls off while covered in grease :nut:
     
  10. NEp8ntballer

    NEp8ntballer cyber ninja

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    I have a buddy who's a diesel mechanic for Flatbed Express. He's sometimes down at their KC location and I can see if he wants to take on a couple hours of work on the side. I don't think he'd charge 250 an hour either.
     
  11. jc2001s

    jc2001s SHO Member

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    Well I can log into my virtual machine at work anytime so just let me know if I can be of any help.
     
  12. Denny

    Denny Taurus Homeland

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    Hmmm it's a good thing I have two Freightliner Chassis Cabs over at Midway Ford Truck Center right now I guess!
     
    Last edited: Apr 1, 2012
  13. LJRuddy

    LJRuddy Pop lock n drop

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    Midway is a lot cheaper but they tend to take forever to finish a repair. I think its because they are always so damn busy.
     
  14. SHOhopefull

    SHOhopefull SHO Member

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    Damn... I'm glad I'm not an O/O and stuck in KC with a problem LOL
     
  15. Off Road SHO

    Off Road SHO Moderator Staff Member

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    Before I took anything apart on that engine I would go around with a screwdriver/nutdriver and check every hose in the intake tract. If all are tight and show no signs of leakage, only then would I check the CAC and I would remove it to do that.

    Pressurize it to 6-20 PSI and hit it with a solution of dishwashing soap and water. I use a cup of soap to a quart of water. This thick solution of soapy water will allow you to see bubbles from a "zero" leak, which would blow out a thin solution.

    Tom
     
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  16. sho'noffmtx

    sho'noffmtx Many SHO's

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    i had similar symptoms on my dodge a few yrs ago. ran warm when pulling, low on power, etc. turned out to be the waste gate was rusted up. it too sounded like it was building boost but obviously wasnt after i found that. maybe that will help
     
  17. LJRuddy

    LJRuddy Pop lock n drop

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    I still have not been able to look at it. Bossman can't say no to a job so he constantly has us overbooked to the point where we can't pull a truck off the road for a half day. Guess I'm stuck driving the minimum speed limit on the interstate :nut:
     
  18. NEp8ntballer

    NEp8ntballer cyber ninja

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    if you aren't putting up signs you're losing him moneys.
     

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