Splitting cases when silicon sealant has been used

Hallo all,
I am posting this also here as the results may be broadened.

I'm rebuilding a T140V year 73 and am trying to split the cases with no results. It seems they have been sealed with silicon as per the rest of the engine.
All fastners are removed and no metal tube is present in the foremost mounting. I am simply going potty trying to separate them without damage.
My next move is to dash into the building market and buy gasket remover to see if that will weaken their grips.
Does anybody have ideas which could help, they would be much appreciated.

By the way I have returned from the market and have sprayed the joint, poo that stuff really stinks. Well I will leave it overnight and try againin the morning.

You haven’t forgotten the two screws inside the crankcase mouth at the barrel flange have you?

Many do!

You can rig up a makeshift puller to locate in the alternator stator mounts and pull the drive side half off of the crank.

But normally, patience and a good hide mallet should suffice.

Do you mean the grub like screws where the tappet blocks sit?
They are not on this engine and the two bolts outside of the blocks are also off.

Silicone sealant, IMO, is a tool of the devil for many reasons, one of which is what you are experiencing. I ONLY use it in very rare instances - none on any motorcycle I have owned. But my opinion doesn't help you any...

As far as releasing it, if you can't work a razor blade into the joint, it can be a real PITA. Years ago some of the available solvents could weaken it but AFAIK, none of them are available nowadays or are so drastically weakened (Thanks, OSHA!) that they basically don't work. Some folks claim they have some luck with gasoline but that probably depends on the silicone (and the gasoline) - easy enough to try it.

If I was doing it I'd try some heat...not because I "know" it will work (because I don't), just based on the fact that enough heat will usually break down anything. Maybe some heat will allow enough "flex" to get the razor blade in. For that matter, you might have to tap the blade (single edge blade) in with a small hammer and just keep working your way around.

The puller thing described may work. I am not familiar with that engine case/the mounts described. But a possible problem with that is that the puller will apply uniform pressure and the entire ring of silicone will be resisting it. Be careful of the amount of pressure you apply with a puller - it might damage the case rather than the silicone. Can you rig up some sort of large bolt/nuts/blocks of wood to act as a "pusher" from inside the case on one area of the joint? That would make it much easier to get the separation started or at least to be able to work the razor blade in. Once the blade gets in you should be able to just move it, or use additional blades to work your way around.

GOOD LUCK!!!!!

MexicoMike's "pusher" idea may be facilitated using turnbuckles and wooden blocks.

Is it possible to place a blanking plate over the cylinder base area, seal all the holes in the cases, then using a Schrader valve fitted to the blanking plate, apply air pressure? It might just pop apart if do-able. A bad crank seal might doom this idea.

Good luck with it.

Slick

I've been trying an operating scalpel which is way sharper than a razor blade with no luck, it is unbelievable how well butted on each other the cases are.
Later I will get some gas and try the heat method.

Is a scalpel as thin as a razor blade? I have no idea. If it is, then, of course a razor blade wouldn't be any better - other maybe than the fact that you wouldn't be reluctant to tap on a razor blade with a hammer to force it in as opposed to possibly damaging the scalpel.

Try the heat method and the gasoline method separately!

If neither method works, I'm confident (easy for me to say, I'm not the one who has to do it) that the pusher method with the device between the crankcase halves as close to the jointed area as possible (not in the middle of the opening) will break it loose.

Pour gasoline into the crankcase and let it sit overnight?

That's what I'd do if I was trying that method. Cover the opening at the top of the crankcase with tinfoil.

Have you tried a hot air gun on the high setting - maybe even direct it inside the cases and get them good and hot. When anything sticks that's my "special" tool and it often works.

In my sailboat racing days, I would always encounter a product called 3M 5200 sealant, which I think is silicone or Polyurethane...but it just about the most tenacious stuff conceivable. Used on flanged plastic hatch covers bonded to fibreglass decks etc, usually the deck would de laminate before the plastic would let go if 5200 had been used.
One day I came across a product the specifically claimed to release 5200...Debond Marine Formula 2000. Got a few cans and found really did the trick.

Here's a video I found back then, still up today:




I believe I still have a couple of unused cans about,

could send one to you if you still need?

5200 is not silicone so I don't think that release agent would work in this case but, heck, can't hurt to try.

I used a LOT of 5200 in the marine world, where as you noted, it is the king of adhesives. The rest of the boat would come apart before the 5200 joint would! Due to its tenacity and near impossibility to remove, the old story was:

Marine Mech to new assistant: "If I tell you to use 5200 on something, ask me again.
If I again say yes, assume I'm drunk and ask me again tomorrow.
If I say yes then, go ahead and use it but I probably won't."

Fast Eddie said

You can rig up a makeshift puller to locate in the alternator stator mounts and pull the drive side half off of the crank.

Click to expand...

I concur with Nigel. When I was trying to split my T160 crankcases using the typical standard measures, I tried and could not move them and was getting scared that I would knock a piece of alloy off. I got a piece of sturdy aluminium or dural and drilled holes in the same position as the stator bolts and using the studs (unless I used appropriately sized bolts into the stud holes...can't remember) screwed the plate onto the end of the crank putting moderate pressure against the crankshaft, smacked the crankcase as before with the rubber mallet and lo and behold, the crankcase started to separate immediately. Obviously you have a T140, but it will work just the same.

Regarding silicone, I have always found that paraffin will turn it to mush quite quickly. Whether or not it could permeate between the crankcase joints, possibly but probably not.

In the past I have used the petrol approach. It took days of soaking but eventually it worked. No idea if this was just my particular
set of cases or not. Naturally if you have a leak and you cannot get the cases to split you do wonder just what is going on!

MexicoMike said:

5200 is not silicone so I don't think that release agent would work in this case but, heck, can't hurt to try.

I used a LOT of 5200 in the marine world, where as you noted, it is the king of adhesives. The rest of the boat would come apart before the 5200 joint would! Due to its tenacity and near impossibility to remove, the old story was:

Marine Mech to new assistant: "If I tell you to use 5200 on something, ask me again.
If I again say yes, assume I'm drunk and ask me again tomorrow.
If I say yes then, go ahead and use it but I probably won't."

Click to expand...

Yes, 5200 is in fact Polyurethane...but from the Debond product description it states also works on other silicone sealants. It is not a nasty product...smells like orange rinds so likely has some of that in there as powerful degreasant/solvent.
I would try scoring as much of the joint as possible with razor, and spraying something like penetrating oil...just to get it seeping under the adhesive/metal surface...most automotive silicone sealants I've come across do release from metals once oiled sufficiently and force applied.

Digisel- Made by RPM specifically for this

Reggie said:

Regarding silicone, I have always found that paraffin will turn it to mush quite quickly. Whether or not it could permeate between the crankcase joints, possibly but probably not.

Click to expand...

“Paraffin” being kerosene/heating oil/lamp oil in this case. Doesn’t evaporate off quickly like petrol does.

I must say, silicone sealant has never given me serious dismantling problems.

One way to avoid silicone gluing the parts together is to put a thin smear of oil on one of the mating surfaces. Then, when putting the parts together, it will still seal but not adhere to that side. HOWEVER, a better way to avoid it is to, as Nancy Reagan said, "Just say no!" to silicone sealer (except for your bathtub/shower)

Never had a problem with silicone, just be aware to buy the non adhesive gasket type, which is not always clear on the box or tube.

I can at last put a happy end to this thread.

After much heat, the razor blades driven in (great trick), more heat and a final thump with a rubber mallet came that gratifying 'click' they had parted.

It was a well and truly an awful smear of gunge which luckily had not starting parting on the insides of the cases.

My thanks go to you all for the great help and advice.