The joys of disassembling

[n3480h]

Rebuilding the 2180 I bought last year. Teardown was pretty uneventful, mostly just keeping things identified and bagged to protect them. The engine has Mahle pistons and cylinders, and at 56 hours TT they look very good. Then comes the red RTV scraping - boy that's fun! The trick is to scrape it off without scratching the aluminum case. Got all that done, washed the case down with solvent, brushed off the dirt and used paint stripper to remove the black paint that was on it. No cracks, whew! The case is back on the breakfast bar, sporting a nice coat of hammered aluminum paint and looking new again. I would have gone shopping for high heat emmisive coating, but this engine will have very adequate cooling. Now its on to cleaning and painting the small parts, preparing for reassembly.

Oh yeah almost forgot the most fun part: The gland nut. This was assembled per the GPASC manual; the gland nut is torqued to 250 ft lb with blue locktite. Getting it off will definitely strain some glands. The assembly manual does not tell us to hire a sumo wrestler with a 6 foot breaker bar, but it should - even if its not a disassembly manual. Two days later, my voice is almost back to its normal pitch. All part of the fun.

Tom

[peterzabriskie]

Glad you got your voice back Tom...ha ha. Hammer Alum paint should look very cool, any advantage to painting case to show up future cracks? I rebuilt Christine's ' Datsun brakes when we first met on the dinningroom table, part of our marriage vows were that I would never do that again. Ha ha ha ha.
-Pete

[oahupilot]

If you have not put the case back together I recommend not using rtv on the parting faces. I use gasgacinch (permatex form a gasket works well too) then lay down 2 threads of 00 silk thread. The case parting face requires a thin film sealer and which rtv is not. This can lead to improper preload on the case studs regardless of what the torque wrench says, also the rtv that squeezes out of the parting seem can fall into the the case and clog an oil passage.

Only apply the silk thread to the parting face not the any of the bearing surface, keep the thread off the case studs as well.

[n3480h]

Alex, thank you, this is very good advice. I learned it from an old A&P. Silk thread and Gascacinch are on hand and ready. And you are correct about the RTV clogging oil galleys - I found 2-3 that were significantly (80% ?) restricted by squeezed out RTV. Had this been any worse, I believe the previous owner would have had a big problem with the engine.

Pete, funny stuff about the brakes. Yes I wanted a light color to help identify any possible leaks. Black or any very dark color would not help with that. The engine will be full-flowed, filtered, and I have a large cooler to be positioned under the sump. Cabin heat will be fed off of the cooler's baffle.

Tom

[oahupilot]

Tom, in regards to paint it tends to be somewhat flexible and may actually mask cracks, they do make a specific paint that does crack along with the substrate. In the army we referred to it as trucrack but what its real name and were you can get it I am not so sure about.

The flip side of the coin is that most visual inspections will not show you the start of the crack, unless you open the crack up with some heat. I have seen some helicopter engine mounts that passed a visual inspection but then failed a torque test, turned out that one of the locking rings was cracked. The Crack was so fine you couldn't see it with the naked eye.

Also cracks will probably start around the bearing saddles requiring you to actually look inside the case. This is something better left for overhaul. If you were really worried about the case you can get it checked out with dye or mag flux.

The only time I look for case cracks is at annual and overhaul.

[hans]

Of course I know Gascacinch, but what is Silk Thread? What is it used for, how is it applied, why is it used?

thanks,

Hans

[splischke]

Silk thread has been used on Lycoming cases for many years. Here's an article with pictures of silk thread being applied that should help answer Han's question:

www.meyette.us/SuperiorTextPics.htm

While the use of silk thread is common practice on Lycomings, up until now I haven't heard of it being used on a VW case. Interesting. How many people on this forum use silk thread on their VWs?

-Scott

[n3480h]

Good article, Scott, thank you. To be specific, the VW bearing boss thru bolts already have a "seal" in the form of an O ring. As the article states, there is no need to put silk thread at these locations, and doing so may contribute to thru bolt/stud failure on Lycoming engines. ON a VW it would just be redundant and may do harm. I still plan on the 00 size silk thread on the perimeter case parting surface, one side only.

Oahupilot, I agree with what you said about paint possibly hiding cracks. Eventually though, oil will leak. At that point I will find the leak. And yes, the interior of this case was carefully checked visually for cracks. I will admit to using a magnifying glass 'cause I'm real d**n old. Nothing suspicious was found, just more fine bits of RTV. Curious - how does magnaflux work on an aluminum case? Seems counter intuitive. I've used dye penetrant with good results, but never used magnaflux.

Tom (Assembly lube in hand)

[oahupilot]

Tom,

Yeah sorry your right you cant magnaflux a an aluminum case, what I meant to say was eddy current test.

[soneraifred]

All I've ever used on both VW cases and my Lycoming case is Loctite 518. Lycoming says that if you use 518, no thread is required.

[n3480h]

Lol, well this is the information I wanted. I wanted different views, but Fred, I don't think I want to disagree with you or Lycoming on this issue. I talked with another friend today who also recommended 518.

Thanks to all who responded - I've learned something useful and important to the success of this rebuild.

Tom