Topic: Internal engine case coating?

[millerza]

So I was stripping the cases with methylene chlroride and a little got on the coating inside. I didnt think this was a big deal, but I was curious about the coating. I had thought this coating was just like a stain caused by oil/heat? It came off like paint. So whats the deal with this stuff? Its purpose? Can someone affirm that some coming off from stripping doesnt matter. Will it peel more from this spot.

[Bodi]

In my experience there is no paint like coating on the inside of the cases. Obviously some PO could have done that though. I have seen old engines with a varnish/glue coating on the insides from decades of running with rare oil changes. It can peel off in sheets.

[Nikkisixx]

I'm with Bodi.  I've never heard of any coating used in old Honda cases, but is is possible.  More likely it is paraffin or some other gunk out of the oil or perhaps an additive like slick 50 or STP stop leak. You will want to get it out of there if it can flake off and do bad things.

[millerza]

ok heres a pic. Im talking about the goldish stuff on the alum pieces.

So is this a stain? Would anyone see a need to remove this.
Ive washed and scrubed it so its clean, but this stuff stays like a coating.

[wannabridin]

that's an oil stain from heated oil and somewhat porous aluminum.  years of hot oil sloshing around the cases will stain them.  as for getting it off, i'm not 100%, you'd have to let some of the guys w/ more experience chime in

[Lavis500]

I don't have terribly much experience myself, but I can tell you that I cleaned a very similar oil stain from the pan of my 500 with a sonicare toothbrush (or a sonicscrubber if you wish, since they are much cheaper) and some kerosene. It went from brown to shiny, new-looking aluminum!  I'm sure that any amount of elbow grease with any scrubbing device would work.  Kerosene was recommended in my shop manual for cleaning engine parts, and it seems to do a good job.  As for whether or not you NEED to clean it - I don' know.  My guess would be that a clean engine is a happy engine, reduce carbon buildup to reduce friction and yadda yadda blah blah.  I don't think removing it would hurt, that's for sure. 

[millerza]

Ok Im going to remove it. The methylene chloride I oversprayed seemed to remove it pretty well.

THANKS GUYS

[SKTP]

You are so lucky...my entire engine is Dirt on top of black grime on top of burnt gold...every part! good times.....

[Retro Rocket]

I would probably keep any solvents from touching the bearing surfaces just to er on the side of caution, don't want to damage them..

Mick

[ekpent]

I wouldn't worry about the color just worry that there is no grime or grit and do not introduce any,keep those oil passages,bearings, nice and clear. Color is just some patina,call it a pre-treat,as it will just come back again someday.