Correct direction for 440 rear main seal seating

[75Travco]

Sent: 5/21/2006 8:36 AM

The replacement seal is molded rubber, which is very different from the original rope-type seal.  The installation instructions explicitly state, "main lip shall face front of engine", but there is no diagram or illustration of the correct installation.  I put the seal into place, but it looked a little strange.  Most of the lip-type seals that I have installed have the lip facing the outside of the engine - like the timing cover seal.  This covers more of the sealing land on the crankshaft, and would provide less opportunity for dirt to work under the seal.

[denisondc]

Sent: 5/21/2006 8:29 PM   I am going to guess that you have it installed the correct way.  If the instructions say to do it that way, thats how I would leave it.     I have installed quite a few seals in engines over the years.  The typical front main seal has a lip with a spring behind it.  And that side of the seal is -open-, whereas the other side of the seal is the -closed- side, also known as the flat surface you use to seat the seal into the block, timing cover, or whatever.  Installing the seal this way leaves the part of the lip that contacts the spinning crankshaft or camshaft to be facing -in-, toward where the oil is, that you want to keep from getting out.   The rear main seal you have doesn't have that spring in it, or the space behind the seal.  But the lip is facing -in-, toward the lubricant you want to control, as I would have expected  it to.   If it were turned around, there would be the possibility of the oil pressure from the bearing, acting on the space between the crankshaft and the seal, trying to -lift- the seal off of the crank.     Now I hope you are able to slide the metal casting up into place, that holds the bottom half of the seal up against the crankshaft.  I had problems trying to keep the two rubber pieces that slide in the grooves on each side of the casting from getting squished - instead of remaining in the grooves and sliding up into place to complete the seal.    It took several tries. 

[Slantsixness]

Sent: 5/22/2006 7:35 AM the lip facing inward like in your picture is correct. Although lots of people do it, resist the urge to trim the seals on the crank side to make them fit better. when you replace the oil pan with the new seal on it, the main seal relies on the tab edge of the oil pan rear seal to hold it from moving. Dab a little silicone on the oil pan seal tabs (where the bottom seal fits over the rope replacement seal , it will ensure a good overall seal. Tom