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  View original topic: Type 4 engine tin cleaning/ degreasing
Jim981 Sun Aug 31, 2014 3:07 am

Hello from Australia everyone. I am currently doing a rebuild on my type 4 2.0 litre engine. Most of the engine tin is there, but as expected alot of it is in a grimy, greasy condition. I dont have access to a shot blast/ sand blast cabinet. I am considering running all of the tinware through a caustic soda bath. Has anybody else done this before? What sort of results did you get? I want to do it right the first time and not need to strip it down after a year for a repaint due the paint lifting.
Most of them have come good with a degrease and scrape. However the flat plate at the rear just below the cooling fan has grease up inside of it. Any assistance here would be of massive benefit. Thanks. James. 8)

aeromech Sun Aug 31, 2014 8:24 am

You could do it the hard way using gasoline and a brush. Hot water with simple green works too. Plan on getting dirty. Squirt things Down and let them soak first

merlinj79 Sun Aug 31, 2014 8:25 am

Do yourself a favor, maybe get it all powder-coated. Otherwise it's hard to clean and paint that stuff so it will stay painted.

raygreenwood Sun Aug 31, 2014 11:05 am

As aeromech noted....let it soak. Depending on which parts of the tin and how oily it all as and for how low....you will find alternating layers of grease and dirt hardened together. Because of this....no single solvent will remove the combined mess easily.

A solvent will dissolve the grease/oil but do little to the combined dirt. It becomes a penetration issue. I have found hot water and a very strong detergent soak in a large tub...followed by high pressure water from a pressure washer or car wash does best.
It will get you down to paint and a fine film of dirt that is hard to remove.

At that stage....you could use caustic soda because it will remove the paint and dissolve the rust. What works easier and safer at that point is an aircraft stripper. It will remove the paint with the fine film of dirt. Them high pressure water and detergent, then an acid wash (60/40 muriatic swimming pool acid to water....wear splash proof goggles and respirator...same for caustic acid).

This will remove all rust down to pristine metal. It will then promote flash rusting overnight or faster. let it rust.
Then hit it with a phosphoric acid product like ospho.

The phosphoric acid converts the flash rust to black iron phosphate....which will not rust....and makes ideal primer for top coating. the more even the flash rust...the more even the conversion coating....and the better the primer.

You can then use a high quality spray can epoxy....no primer coat. This will last for eons and be tough as nails.

Powder coat is nice....but I have found it not to be the best for engine tin. ts too thick. You have to clearance around holes and threaded nuts. If you expose metal...it will rust and undermine the powder coat. I have found it to not last any longer than good epoxy. Most normal powder coats will be more susceptible to attack from solvents and gasoline than epoxy.
Those that are not....high temp chemical resistant powdercoat....are much more expensive. And with powder coating....the powder coating is only as good as the surface prep work and degreasing. Ray

Jim981 Tue Sep 02, 2014 3:34 am

Thanks guys. I really appreciate the help.

Currently alot of it is soaking in either diesel or hardware store bought degreaser. I am getting it off quite well, but want the pristine ready to paint tin as painless as possible. I wanted to speed up the process for the better where I could.

I was also only going to toothbrush/ paintbrush scrub the block, because I didnt really want to split it and worry about setting it up right again. Its a bit out of my comfort zone. Has anyone found any pitfalls from doing this? May need to do it anyway just to know all of the old greasy gunk is gone and the blocks all clean. Thoughts?

aeromech Tue Sep 02, 2014 4:20 am

Try to avoid getting water inside

Jim981 Sat Sep 06, 2014 11:35 pm

Am just going to bake it in the sun for a good day or so. Well I have summer coming up shortly. Will split the case, scrap most of the grease off, find a good 35c plus day to pressure wash it on and let the sun sort it out.



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