Click for JetForums Click for Mag Bay Click for Llebroc Click for Lurssen Click for Cheoy Lee

Man Thermostats

Discussion in 'Technical Discussion' started by CSkipR, Aug 8, 2019.

You need to be registered and signed in to view this content.
  1. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    On my starboard engine we removed the 3- 86 deg C thermostats. The rubber on each of the thermostats is destroyed. The rubber looks like it was eaten up. No problem on the thermostats on the port engine. Both engines have the Man approved coolant in them. When we were removing the heat exchanger on the starboard engine we found alot of rubber pieces but didn't know where it was coming from until we removed the thermostats. No one from Man has been able to explain why this has happened.

    Attached Files:

    Last edited by a moderator: Aug 8, 2019
  2. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    7,033
    Location:
    Satsuma, FL
    Did you just replace these a few ago?
  3. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    7,033
    Location:
    Satsuma, FL
    How did the big O rings on the HE end caps look?
    Looks like a bunch of RTV peelings also.
    Next place to wonder about is the flat gaskets in the oil coolers on the stb side of the blocks.
    When were they last serviced?
  4. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    Capt Ralph,
    You are correct they were replaced about 3.5 years ago. The 3 that were removed 3.5 yrs ago one looked similar. O rings in the HE end caps looked fine. As mentioned we did find rubber in the HE that we were unsure where it came from. We did think it might be RTV sealant but it wasn't. I did notice that the 3 thermostats did smell somewhat like diesel fuel and I've heard of something called cavitation created by lack of SPA in the coolant although I'm not familiar with it. Any thoughts?
  5. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    7,033
    Location:
    Satsuma, FL
    #1 send a coolant sample to the lab for level 1 and II testing.
    Other than combustion gases, it's not raw fuel you are smelling. Fuel pump has weep holes that would not mix coolant with fuel if it was leaking. Worse case; in the oil sump.
    You did not mention if the oil coolers were serviced. Oh, Back block gasket also? I'm still leaning to much sealant (of some kind) when they were re-sealed.
    Cavitation is an abused word. It is suppose to be high volume (sonic?) water wear around the lung walls. It does not make rubber.

    OTOH, you were doing the MAN HE per maintenance schedule or having troubles? If no troubles, slam it back together and go fishing.

    From my old school, grease makes a better low pressure gasket dressing than RTV or GOOP.
    It's the gasket or seal that should always be doing the work, not the glue or something is wrong.
    I do know that back block gasket to end plate before the flywheel adapter, There is something wrong there. On re-seals people use goop. Like the oil cooler, if grease was on the gaskets, they would not tear when distorted. IE torquing a hose to the cooler housing. IE the engine block torquing over from the clutch and flywheel adapter.

    The V8-900 has to be one of the sweetest packages MAN put together for its weight. Hate the electronics.
    Sorry nobody up here (or your way) can work on them well. I took the baths the hard way. I luv/hate MAN packages. Still lots of my blood mixed in those bilges. Thank goodness those boats are out of here,,,,, Down Skippy Js area now...
  6. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    Ralph we are performing general maintenance on the HE and intercoolers. The oil coolers don't get serviced. Oil cooler gaskets were replaced several years ago as that was a common problem with this particular engine.
    Will send antifreeze off for testing. This is definitely not RTV or any gasket sealant. It is the rubber particles that have come off of all three thermostats as you can see in the picture. Obviously something is causing the rubber on the thermostats starboard engine to deteriorate.
  7. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    7,033
    Location:
    Satsuma, FL
    Like a O ring seal on the stats edge?
    Were these OEM MAN stats?
  8. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    Yes and Yes
  9. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    7,033
    Location:
    Satsuma, FL
    And you said MAN does not have a clue. You asking my MAN shop (Performance Diesel) in Houston?
  10. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    11,084
    Location:
    Fort Lauderdale
    Was the starboard engine ever overheated? Are they using the Texaco long life antifreeze that is spec'd by MAN?
  11. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    No I checked with several shops here in Florida. Since Performance Diesel quit shipping parts to Florida I no longer have a contact there.
  12. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    Capt J no neither engine has ever overheated. Not sure which antifreeze you are referring too. The antifreeze was recommended by a Man representative. It was orange Valvoline Ext Life Dex Cool. There are a few others like Delo ELC or Zerex G48 & Zerex NF EL Yellow. As usual Man makes it difficult to find there recommended brands and products are not always easily located.
  13. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    11,084
    Location:
    Fort Lauderdale
    Tell me about it. I've been dealing with a handful of new European boats in the past year and most have MAN's. All of the Man's have a blue coolant in them (similar in looks to the cummins stuff). None of the MAN local dealers have it nor know where to get it and they recommend dropping it and changing it to the pink/red. The local MAN dealer here uses and says that MAN recommends the Texaco coolant, they didn't mention any others but that is not to say that MAN doesn't recommend others.


    http://www.matweb.com/search/datasheettext.aspx?matguid=35545412a84a4792a797f83d3e918eaa
  14. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    Here's an approved Man coolant (Zerex G 48 - $25 gal ) which I got from NAPA. It's blue. This is listed on Man's approved list from Germany. There were three other coolants that Napa could get although would have taken longer and I believe are all approved. Chevron Delo XLC, Chevron ELC and Zerex NF EL Yellow.
  15. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    11,084
    Location:
    Fort Lauderdale
    Thank you, as I had no idea where to get the blue coolant (for top off) that these new MANs are coming with. Both a Fort Lauderdale dealer and a Palm Beach dealer told me they don't have it and don't know where to get it.
  16. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    7,033
    Location:
    Satsuma, FL
    There is this real cool group of fine people I know. Ask them anything on YachtForums.com and they can help find the answers you need.

    :cool::cool::cool:
  17. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    4,372
    Location:
    Miami, FL
    Tstat lasting 3.5 years.... reallly?
  18. CSkipR

    CSkipR Member

    Joined:
    Aug 16, 2008
    Messages:
    910
    Location:
    New Smyrna Beach, Fl
    Yep that's what I said too and at $250 each times 6 is ridiculous. Here is an article I read last night regarding antifreeze. My antifreeze was replaced 3-1/2 yrs ago.

    The coolant can become more acidic over time and lose its rust-inhibiting properties, causing corrosion. Corrosion can damage the radiator, water pump, thermostat, radiator cap, hoses and other parts of the cooling system, as well as to the vehicle heater system. And that can cause a car engine to overheat
  19. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    4,372
    Location:
    Miami, FL
    I don’t remember changing the Tstats in the 3412Es I used to run... 10 years 4500 hours
  20. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    11,084
    Location:
    Fort Lauderdale
    MAN recommends changing the coolant and heat exchanger caps every 2 years. IMO it is crucial on them and I do it religiously on MAN boats that I maintain. I believe the MAN's are pretty hard on coolant and it can become acidic and cause issues. I follow the book on everything with MAN's except the cleaning of the heat exchangers every 2 years. I do those every 1000 hours or 5 years or the first sign of a loss of cooling capacity.

    I just find it odd that it is on one motor and not the other motor. Is it possible you got a bad gallon of coolant or something else got dumped in there.....It also could be possible something else is leaking into the cooling system, such as fuel, salt water, or exhaust gasses, I would have a lab test it.

Share This Page