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Coolant in cylinder after storage

in 912 / 914 Technical Questions 10 years ago
I have a 1300 hour 912ULS from a wind-damaged 2008 Remos that will have a new life in a homebuilt. The engine sat for a year, and when I got it had about 1/4 cup of coolant in #2 cylinder. The sparkplug electrodes were rusty. There is no visible water in the oil drained from the tank. The engine was hydrolocked due to the water but I doubt that anyone had tried to start it (the nosewheel was trashed in the wind damage, so there would have been no room for the prop to turn although the prop does not appear to have been damaged.) The top of the piston and cylinder walls look OK with a borescope, I'll pull the cylinder head off soon. The 3 other cyls look OK and have some compression. Otherwise the engine looks OK, logs show regular 100 hrs and SB compliance by the same A&P since new.

The engine is one of the 1500 hr ones that can be upgraded to 2000.

Can this be anything other than a crack or corrosion pinhole in the head? Anything to do but find a replacement head? Should I try to clean up the cylinder and run the engine as is?

  • Re: Coolant in cylinder after storage

    by » 10 years ago

    David,
    its very rare to have porosity or a crack in the heads. How bad was the impact damage? Maybe the coolant came from a split hose through a broken induction manifold? maybe it is just rain water that changed color with residual lead/carbon in the cylinder?
    You can test the head by pressurising the coolant gallery with air and putting the head in a bucket of water.
    Rob
    Thank you said by: David Josephson
      
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  • Re: Coolant in cylinder after storage

    by » 10 years ago

    Hi David,

    I received your PM on this.

    I agree with Rob that this would be highly unusual. I would pull the head and clean and inspect that cyl. Do a good differential compression test and see if any test air comes back into the coolant or do as Rob suggest. I would be really surprised if it did, but something just to rule a breach in the head in or out and it's free and easy to do. If you find nothing and compression is good then run it for 20-30 minutes and check it again then keep a watchful eye on it for a few hours.

    Good luck. I hope it's nothing so you can concentrate on building and flying.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: David Josephson
      
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  • Re: Coolant in cylinder after storage

    by » 10 years ago

    Roger and Rob,

    Thanks for the responses. There wasn't much impact damage at all, the airplane danced around in a t-shelter (not tied down, in an early summer Texas windstorm) and the wingtips, prop spinner, nose gear were bashed, the tailboom tried to fold around a steel beam. I don't see any damage elsewhere in the engine at all -- not a scratch on the cowling or prop. No hoses split, coolant tank still full (none in the overflow bottle, though.) But when I pulled the upper plug, I got a slug of coolant when I turned the prop, and it was fluorescent green just like the coolant. When I took the head off this morning it was still wet inside the exhaust port, with a mixture of aluminum corrosion and water-loosened lead deposits. Clean and dry in the intake passage. What else could have put coolant into the exhaust port?

    I will see if I can make the coolant passage blow any bubbles, that's a good suggestion -- thanks!

    When I visited ASOD to inspect the plane a few weeks ago (and decide whether it was a project I wanted to take on) I had only a static compression gauge, didn't get more than 100 lbs on the other cyls, and none on this one. I expect I will have to lap valves and seats for diff compression to make any sense. Is that consistent with sitting for a year?
      
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  • Re: Coolant in cylinder after storage

    by » 10 years ago

    Hi David,

    You can't lap these valves. They are armored and are super hard. You can clean them, but if they are damaged they need replacing. A good soda blaster works wonders on cleaning up parts and unlike a sand blaster won't take off any metal or coatings. The cylinders are a nickle composition and too hard to hone, but can be cleaned if that is all that needs to be done. You will most likely need new rings. The head needs to be lapped back in place as there is no gasket. The valve seats need a special tool to adjust or re-shape the seats. These tools are about $1200. You would be far ahead of the game to just send them into a distributor and have the work done.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Coolant in cylinder after storage

    by » 10 years ago

    You should not have compression problems with only a year of storage. How do the other exhaust ports look?
      
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