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Order Ford 661 Parts Online

661 rear main seal

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Author  [Modern View]

10-25-2016 06:55:25

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Our 661 has a leaky rear main seal, I see the replacement is "rope style" so I just drop the pan and pull out the old and push in the new? Can it really be that easy? Any tips, tricks or warnings?

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Tall T

10-27-2016 11:02:24

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 Re: 661 rear main seal in reply to markct, 10-25-2016 06:55:25  
Yet another thought . . .

If you use the groove in your main cap, to pre-shape your block half of the seal, you will have a much easier time of feeding it into the block groove!

You might want to have a friend be rotating the shaft for you so that you can have two hands free for the process. One hand pulling and the other hand can minimize resistance where the seal enters the sharp edges of the block groove.

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Tall T

10-26-2016 13:23:20

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 Re: 661 rear main seal in reply to markct, 10-25-2016 06:55:25  
Quoting Removed, click Modern View to see


You're welcome.

One final note:

When you apply Lubriplate to the block half of the seal, try and keep it off the face of the seal to minimize the seal slippage on the crankshaft flange.

The reason being that it's a combination of the pulling pressure on your fishing line being just enough to cause the wick to stay with or follow the rolling crank flange. So it's as much or more the crank that is rolling its own seal into position as you pulling it in. The less slippage between seal face and crank flange at that point, the better for installation.

As far as the cap half of the seal goes you can lube the face as well of course, but if you keep the seal mating ends DRY, then you can put small dots of Permatex #2 where the wicks meet if you like.

If you use strong fishing line, you could actually with a needle run a couple of passes right through the wick before wrapping and tying it. The more your line puller is centered off the end of the wick, the better as well.


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Tall T

10-25-2016 19:39:35

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 Re: 661 rear main seal in reply to markct, 10-25-2016 06:55:25  
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Remove the cap, the old seal half and using a round rod (half inch or so) work from the wick ends down into the hollow, FIRMLY working the seal into the groove.

For the block half, grab one end of the seal with needle nose pliers (pliers with good teeth) and pull while rotating the crankshaft in the same direction as removal.


To install the block half, coat the seal with Lubriplate (Bearing Assembly Grease) after attaching strong fishing line or wire to one end of the seal BUT with the wire puller not more than 3/8" from the seal end. Pass the free end of the wire up and over the crank flange.

Then exert a firm steady pull on the wire while rotating the crankshaft in the same direction to help move the wick .
Trim it flush with the block when done.

You can either cut the cap ends of the seal flush with the cap or leave the ends a very tiny amount proud. BUT if you elect to do that then kind of pinch the little excesses into points so that you know they will not interfere with mating faces during assembly. Make sure your thin razor stays perfectly flat on the block and cap so that you don't angle your cuts.

If I were doing this with the block upside down on a bench, it would be the block half of the seal ends that I would leave a hair high. Working upside down it will be trickier to be a perfectionist about it but easier to be accurate cutting the cap ends. The "Proud" idea gives a little wick compression to the meeting of the ends.

I'd better copy this so I don't ever have to type it again. :D

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10-25-2016 20:06:32

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 Re: 661 rear main seal in reply to Tall T, 10-25-2016 19:39:35  
Thank you for the detailed explanation! Sounds doable, I will give it a go when the parts arrive. I'm a truck and heavy equipment mechanic by trade but have never had to do one of this style before so figured I would ask first

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10-25-2016 09:36:42

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 Re: 661 rear main seal in reply to markct, 10-25-2016 06:55:25  
If your leak is the engine rear main, there are two different places at the rear main for it to leak. There is a seal on the crank journal that was a rope type seal originally, but with the age of these tractors it could also be a split neoprene seal if somebody has ever been in there before. The rear main cap is also the back of the engine block and there is a wedge seal on the sides of the rear main cap. The original wedge seals were a paper type that swelled when immersed in oil.
I tried to replace these seals without dropping the crank without luck. There is a tool called a sneaky pete that will help you pull out a rope seal. The rear main cap will contain both one half of the journal seal and both wedge seals. The upper half of the crank seal will have to be pulled out from between the engine block and the crankshaft. I did not have luck with the sneaky pete tool and ended up digging out the rope seal and pushing it out, it was not fun.

I tried the two piece neoprene seal and neoprene wedge seals with metal pins that you drive in the wedge seals to make them a tight fit without success.

I ended up pulling the engine to replace the rear main seals. During disassembly, I found that the engine also needed to be freshened up while I was in there.
Upon reassembly on an engine stand, I used Victor Reinz sealant in the rear main cap wedge grooves and the two piece neoprene on the crank journal. No leaks now for 4 years.

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10-25-2016 13:37:09

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 Re: 661 rear main seal in reply to michford, 10-25-2016 09:36:42  
Hmm, I just assumed it would be rope since that's all I saw available for replacement, is one type better than the other?

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10-25-2016 16:52:26

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 Re: 661 rear main seal in reply to markct, 10-25-2016 13:37:09  
I have no personal experience with installing a rope seal. I did not try the sneaky Pete tool to install the rope seal with the crank still in the block, but they are supposed to be able to. The rope seal might be more forgiving if the crank journal has some wear, where the neoprene is the modern solution for sealing crank journals.

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