Preservative grease
 

When dealing with new-old-stock parts, how important is it to remove the preservative grease and what's the best way to do it? The part I'm dealing with is an M135 differential, but I guess the answer would apply to anything with internal moving parts.

I'm not sure what the consistency of the preservative was when it was new, but 60 years on, it's like a stiff wax. Did the repair depots originally use a hot tank to remove it? I don't have one of those, and a couple of days soaking in my parts cleaner softened the preservative on the outside to the point where a stiff brush would remove it, but didn't make much impression on the internal parts I can't reach.

Will it have to be stripped down to clean it, or can it be effectively flushed somehow? How important is it to remove every last trace, including places I won't be able to scrub, like inside bearings? Will a small amount of residue dissolve harmlessly in the gear lube or will it cause problems?

Boiling (or even tap-hot) water will remove it, leaving a slight water repellent residue on the surfaces. A word of caution, if you run it under the hot tap in the kitchen (no dear, it wasn't me :nono:), it will re-harden when in contact with a cool surface like the sink or drain pipe. A large amount on a sizeable part can be shaved off first (and if you are in the kitchen, don't use the cutlery or knives!) to reduce the amount to be melted off.

When I worked in army workshops, a lot of parts for the older vehicles were like this, especially shell bearings, pistons and ball bearings, here we had a water tank with an element in it and a basket like a chip fryer, the preservative floats to the top and you can skim it off.

I had a brand new diff/ crown wheel and pinion assembly for a WW2 Humber once, and did not have the benefit of a hot tank nor a steam cleaner, had to resort to stripping the whole thing out. Another time I dismantled a gearbox from a wartime armoured car and there was still traces of the preservative in the box, but the bearings were worn out due to the balls being gummed up and skidding in the races.

Perhaps it is simply a matter of finding an effective solvent. I seem to recall that WW2 American preservatives were best cleaned in petrol (gasoline). Not without risk but rapid and available.

David

Actual solvent (and not the water based substitutes) will usually remove the preservative. Gas would work, but as David mentions, there is the risk of flash fire. At least there is no longer lead in it. Heat will help soften it as others have mentioned.

We used to get the sprockets for the M113s heavily laden in preservative. Didn't matter much on the tooth area, but the mating area with the sprocket carrier was critical. Two infanteers with putty knives usually worked quite well.

Cleaning off old preservtive
 

Hi Ed,

I have found household kerosene a good cleaning agent for old waxy WW2 preservative. Still is a flammable material but a lower volatility than petrol.

I once soaked a heavily preservative encrusted CV joint overnight in an old tin can of kero and the next morning it was completely clear of preservative.

Did the same for a paper and preservative wrapped axle in a capped PVC pipe. Again, next morning there was just loose paper and sludge in the bottom of the pipe.

Kero guns can be used too but managing the spray and splash back can be a hazard if not fully thought through.

Cheers,

Cosmoline, it's the best rust preventative I've ever seen. Info on Wikipedia https://en.wikipedia.org/wiki/Cosmoline says that it is more or less what the Egyptians used on Mummy's. You can still buy it http://www.cosmolinedirect.com , and they even sell a remover. I've usually used varsol or kerosene to remove it.

What I worry about is what Richard said ("the bearings were worn out due to the balls being gummed up and skidding in the races."). Gears shouldn't be a problem. There should be enough pressure to force it out from between the teeth. Kerosene, varsol, or any petroleum-based solvent seems to do a good job on the outside, softening the wax to the point where it can be brushed or wiped off, but I can still see a coating and occasionally large globs of the stuff inside where I can't reach it with a brush or rag. It's softened but not removed.

I could try a longer soak, or the boiling water trick, but the safest course seems to be to dissemble parts to the point where they can be brushed/wiped/scraped and inspected.

__________________

Hi Ed,
When some have mentioned softening with kero, they might have only had a light coating on the parts, but the diff I bought had been dipped, it was complete with casing and pinion and there was no way that it would have washed out with petrol, kero, diesel, white spirit, thinners or anything else to hand, it was very thick and hard. In the end I had to resort to running a flame over it to get to the bolts and completely dismantle. I recall boiling a pot of water in the end to dip the parts in, as I do for pistons. As for the gearbox, judging by the tide mark it had been filled with preservative, and probably drained off. I now remember the mainshaft was still coated where the sliding gears had reached their travel.

I think most tricks have been mentioned already, but there are some youtube vids on this subject......mostly on cleaning Russian rifle parts covered in cosmoline. If I remember correctly boiling or steam cleaning was the cleanest method.

Alex