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  1. #1

    Default My Cummins QSB 5.9-380 Diesel is leaking coolant!

    I have twin Cummins QSB 5.9 diesel engines. My starboard engine is leaking coolant. It only happens when I run at full throttle of 3000-3100 rpms. If I cruise at 2700 rpm's or less it doesn't happen. I've checked the reservoir and the hoses leading to the engine and both are fine. I've had the hoses checked and replaced, a number of mechanics on board and no one can find where the leak is.

    Has anoyone experienced this issue?

    Thanks

  2. #2
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,635

    Default Re: My Cummins QSB 5.9-380 Diesel is leaking coolant!

    Put tracer dye in the coolant, run the engine to make it leak and then hit it with the UV/black light. You will see where it is leaking.


    http://www.oreillyauto.com/site/c/de...2323&ppt=C0014
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  3. #3

    Default Re: My Cummins QSB 5.9-380 Diesel is leaking coolant!

    Thanks Chris. Just talked to Cummins and they say there is a bleed hole under the water pump and if the pressure gets high enough it will weep. Which explains the leaking only at full throttle. Sound familiarl?

  4. #4
    Join Date
    Nov 2008
    Location
    Long Beach, CA
    Posts
    215

    Default Re: My Cummins QSB 5.9-380 Diesel is leaking coolant!

    are you finding coolant in the bilge? if not check your turbo and exhaust manifold for cracks.

  5. #5
    Join Date
    Jun 2008
    Location
    Posts
    555

    Default Re: My Cummins QSB 5.9-380 Diesel is leaking coolant!

    If you aren't seeing coolant in the bilge, it must be going out the exhaust. Buick430 above could be on to it if you aren't finding coolant in the bilge. A crack in the turbo exhaust housing can be hard to find.

  6. #6
    Join Date
    Nov 2008
    Location
    Long Beach, CA
    Posts
    215

    Default Re: My Cummins QSB 5.9-380 Diesel is leaking coolant!

    Yes. I just had a bad turbo on a 5.9 QSB on a police/fire boat. using coolant and heavy steam under load from exhaust. Removed turbo and could see the coolant residue on exhaust side of turbo. after spraying the inside down with brake clean several cracks became easy to see.

  7. #7

    Default Re: My Cummins QSB 5.9-380 Diesel is leaking coolant!

    How does it happened ! So it's because problem of the Cummins engine quality ? In the end, did the Cummins help you solve the problem ?

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