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Discussion Starter #1
I seem to fight the same issue with this darn thing every year: Working on a really hot summer day causes the gasket between the TOM body and the rockshaft to blow out. Because this is also the gasket for the hydraulic fluid reservoir, it makes a terrible mess. When it happened this year, I parked the tractor and moved on to other projects which in hind sight was a mistake because the garden isn't tilled, the property I'm caretaker of isn't mowed, it is December in Michigan and I can't plow snow without it. :banghead:

Maybe this will illustrate the design flaw I'm fighting:

image.jpeg

I think the root of the problem is that there are no bolts across the bottom of the TOM/rockshaft because this is where it blows out every time. Due to the tight fit between the rear axle and belt drive pully, there is no way another fastener can be added. I've been fixing it with OEM gaskets and running OEM specified 10w hydraulic fluid; same as iso 32 spec light hydraulic fluid.

This time I'm determined to fix it once and for all. Clearly fixing it the right way isn't working so it's time to try something else. Before I reveal my plan and taint any ideas yous guys might have, I'd like to hear some of your options.
 

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I would stone the mating surfaces to make sure they are as flat as possible. Are you making a gasket? The gasket in this scenario needs to be pretty thin. A thicker one will allow pressure to blow it out. The thinner one has less surface are to push against.
 

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Discussion Starter #3
The OEM gasket is a very thin paper gasket, but it shouldn't be under much pressure as all it is sealing is the reservoir. I hadn't considered the two surfaces to be out of spec with each other since they are both machined castings... but that might make sense.
 

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I would also use a proper gasket sealant such as this Permatex Aviation Sealant. It's my go-to for many gaskets that I want to insure don't leak. Be aware though, this stuff is tough. If you use it (lightly) on both side of your gasket, expect the gasket to be very hard to remove from both surfaces upon disassembly. In some cases I only use it on the one surface that will be easier to clean later.

I don't always use Permatex Aviation Sealant, but when I do, I know I'll have a leak-free gasket. :lol:

You can get this at NAPA or Amazon. :good2:
 

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Discussion Starter #5
I think I will go that route. It sounds like it might work better than what I was planning.

Using a OEM gasket as a template, I cut a pair of copies out of a really heavy manila file folder. In between them I planned on running a piece of .035 welding wire pressed into a thin bead of black rtv. I was then going to spray the outside of the sandwich with copperkote.
 

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Permatex Aviation Sealant. It's my go-to for many gaskets that I want to insure don't leak. Be aware though, this stuff is tough. If you use it (lightly) on both side of your gasket, expect the gasket to be very hard to remove from both surfaces upon disassembly. In some cases I only use it on the one surface that will be easier to clean later.

I don't always use Permatex Aviation Sealant, but when I do, I know I'll have a leak-free gasket. :lol:

You can get this at NAPA or Amazon. :good2:
I agree with Dieselshadow's recommendation about making sure the mating surfaces are flat and also using a good sealant.

I might suggest you consider using a piece of thin aluminum flashing as a replacement for the paper gasket. The aluminum sheeting should seal adequately when used along with a good sealant. It would be a bit of work to fabricate the seal but using some gasket punches should do the trick.
 

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Discussion Starter #8
I found some of that aviation grade permatex and I'll be putting it back together tomorrow after work... Here's to hoping! :bigbeer:

Now, about the fluid itself; I'm using the stuff specified in the JD manual (Straight 10w, iso32 hydraulic fluid). Would going to a different viscosity fluid help this problem? I'm quite sure that the reservoir itself is not under pressure. Because the seal always blows out after heavy use on a hot day, I think temperature has more to do with the seal rupturing than brute force. It could also be a coincidence because it happens at the same time each year.
 

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I bet if you take a piece of sand paper laid it on a small sheet of glass, then rub the face of the housing on the sand paper you will find some imperfections in the mating surface. I use glass as it is usually flat and does not bow much. I kept one from a shelf from a refrigerator we used to have just for this purpose. Sanding objects flat, carburators get uneven for many reasons among other items. Then use a thin gasket . Must be thin as hydralics will push thick gasket material out and blow. That's my story, and I am sticking to it.:laugh:
 

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Have you ever tried to re-torque the cover bolts once the unit gets up to operating temp?
 

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If you do NOT need a gasket to also act as a spacer/shim, then I recommend doing completely away with the gasket and using Loctite 518 or equivalent:

https://www.summitracing.com/search/product-line/loctite-518-anaerobic-gasket-maker

LOCTITE 518 Gel 50ml Tube, Color Red 518, GASKET, USA LOCAL | eBay

It's made specifically for sealing 2 machined surfaces. Make sure the sufaces are absolutely CLEAN AND DRY. Only takes a very thin coat. Use a straight edge to check to make sure the surfaces are really flat or do like someone else said and use fine sandpaper/emery cloth and a piece of glass.
 

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Discussion Starter #12
Have you ever tried to re-torque the cover bolts once the unit gets up to operating temp?
I have not tried that and its a good idea. There is no torque spec'd in my manuals for those bolts and I can't actually get a torque wrench on most of them anyway. The best I have been able to do is to get them tight, but not crazy tight, with an open end wrench.

I did not get out to install a new gasket today, but I will check the mating surfaces before I do. I find it hard to believe that they wouldn't be true; those are very meaty castings which aren't really subjected to a lot of heat or force... Not like the head of an engine is anyway.
 

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Discussion Starter #13
If you do NOT need a gasket to also act as a spacer/shim, then I recommend doing completely away with the gasket and using Loctite 518 or equivalent.
I don't think the gasket needs to be there, but I'm also not completely sure because the connecting rods for both the control quadrant and the hydraulic ram run through that space too. So far I've been putting one in there because that's how it was designed. Even though the overall design is flawed, the gasket was also put there on purpose. I have been hesitant to use any sort of gasket making goop in the past because unlike a modern tractor, the M has no filter on its hydraulic system. Now I'm starting to get desperate so all bets are off.
 

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Virtually all of the mating surfaces I've seen on the tractors I've gone through have had burrs and high spots. That's normal for as old as these parts are. They've seen many years of use along with various loads and possible mis-torqued bolts causes a slight warp of the mating surface. It doesn't take much to allow a gasket to slip out if the surface isn't right.

Here's an example of a stoned surface. You can see where the high spots were cleaned off to leave a smoother, flatter surface.

 

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The suggestions by dieselshadow and SGS are ones I have done in the past and have had great success with. Another alternative gasket I have had success with is thin sheet copper.
 

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I don't think the gasket needs to be there, but I'm also not completely sure because the connecting rods for both the control quadrant and the hydraulic ram run through that space too. So far I've been putting one in there because that's how it was designed. Even though the overall design is flawed, the gasket was also put there on purpose. I have been hesitant to use any sort of gasket making goop in the past because unlike a modern tractor, the M has no filter on its hydraulic system. Now I'm starting to get desperate so all bets are off.
2 good things about the Loctite 518---
It's designed for mating these machined surfaces, and it takes VERY LITTLE to get a proper seal when the surfaces are clean and dry. I recommend spray carb/choke cleaner (2 bucks @wallyworld) on a rag to clean the surfaces.

The stuff that does squeeze out will NOT cure or harden. Allegedly anyway. It has to be completely cut off from air (between the surfaces) before it will cure. SOOOOOooo.....between not requiring much to begin with and the surplus remaining in a "semi-fluid" state, it shouldn't cause problems internally. Disclaimer: YMMV:hide:
 
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