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I am changing the oil pan in my 69, 351W, and would like to change the rear main seals while I'm at it. I was told that I can do this by rotating the crankshaft while gently pulling the old seals out and pushing the new seals in (first one, then the other). Has anyone ever done this before? I would like to change them, but will not tear the engine apart at this time if that is the only way.
 

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Been there and done that many times. While the pan is off is a good time to do it for cheap insurance if nothing else.

Now your pretty well on your way as how to do it but I would suggest to loosen all the other main caps a little to let the crank drop down some and it will also give the upper half of the rear seal some room to get out. It maynot hurt to rotate the crank, but that maybe hard to do unless you remove the spark plugs first and I have never needed to do it at all.


The upper seal half maybe stuck and need a little prodding to get out. You can use what ever to get it started just remember not to use something that will scratch the crankshaft journal. A small wood dowl is good to get it started. I use a small brass punch but you still have to be carefull with it. Once it gets moving and starts around the journal you can probably grab it out by hand.

Its a good idea when installing the new one to oil it up first and offset the 2 halves so the 2 ends dont line up with the parting line of the block. mm
 

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Discussion Starter #3
Rear main seals

Thanks. It doesn't sound too hard. I'll have a lift available to me and that should make it easier to get to everything. Your way makes it sound easier than I originally thought. Should I expect any problem when I loosen the lifts that I should be aware of? Also, what are the torque limits when I tighten them back up?
 

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modifiedmark said:
offset the 2 halves so the 2 ends dont line up with the parting line of the block. mm
Very Important.
 

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If your engine still has the old rope seal you will need to remove the pin on lower cap before installing the new style seal which you want to offset by about 1/4". Also once the seal is loose you can "roll" it out with a little pressure against it while turning crankshaft with 15/16 on a bar. Once its rolled enough a screwdriver preseed against the seal and push should get it rest of the way but as mentioned, don't mark the crankshaft. When the rear main cap is off if the bearing is worn do them as well and if the mains are gone so are the rods. Mains roll in like rear main seal does. Takes about 5 hours to do bearings seals and pan from start to beer. Be absolutely certain that the seal goes in correctly or it will suck oil out instead of holding it in. You'll need to look at the lip and decide what is correct. Good luck.
 
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