Ford 2.3l / 3.0l / 4.0l rear main seal installer tool

By Al Savage

(Built for, and tested on, 1989 Aerostar 3.0l; it is assumed that it will work for the 2.3l and 4.0l, but I’d appreciate feedback from folks who try it on those engines.)

The problem: These engines use a modern, full lip seal, which is easily removed…. . . . but not so easily installed. You might try to beat the seal into place, but without a way to spread the insertion force to all of the seal’s outer shell evenly, it’s very easy to permanently damage the seal by deforming the outer shell.

Ford & Chilton’s recommend using a Ford rear main seal installer. The problem is that this tool is fairly expensive. The OTC equivalent is No. 7786, and runs nearly $100 (sourced via NAPA, without discounts). Faced with this, and not wishing to lay out $100 for a (I certainly hope!) one-time-use tool, I visited my hardware store and started brainstorming. As usual, the plumbing section was very useful.

Raw materials for homebrew installer

This picture contains:

  • Handful of 3/8" flat washers, grade 2 ($0.50)
  • Flatbar, .25" x 2" x 4.25" ($2 for material, $1 "cut fee")>
  • (2) 10mm x 1.00mm x 50mm long, grade 8.8 ($1.45 ea)>
  • (2) 10mm flat washers, grade 10 ($0.30 ea)
  • Black ABS 4" pipe plug ($3.89)

As it happened, the bolts could have easily been only 35mm long and worked fine, but I didn’t know that when I was at the store.  Hence all the flat washers. The 10mm bolts are extra fine pitch, and probably aren’t stocked everywhere — I just happen to have a very good hardware store near me (they’re getting rare).

I also needed a 27/64" drill bit ($7) (see below).

The seal’s OD is close to 4.25"
The pipe plug’s OD is close to 4.375"
4" ABS is about 4.5" OD

When I was at the hardware store dreaming this up, I wasn’t certain how much clearance around the seal I’d have. For the 3.0l engine, it looks to be a safe bet that you could use a section of pipe, or a different fitting, rather than a pipe plug, and this might buy you more "throw" — more on this later.
 First, I hacksawed off the "square" from the pipe cap:
4 ABS pipe plug, with square wrench area removed

Then I "machined" the flat bar a bit, to reduce the corners:
Removing the corners a bit on the flatbar reinforcement
Yes, that’s the flexplate I’m using as a mill table — when you don’t have, you improvise.

For the 3.0l, this shaping isn’t really necessary, as there’s plenty of room at the rear of the crank, but the 4.0l might really need it.

This is the resulting "fit":
flatbar on modified ABS plug

Now for some layout work:
layout of flatbar, to drill the holes
I did this strictly by eye, it’s doesn’t need to be perfectly concentric. Detail-oriented folks could probably use a lathe and burn an afternoon on this. The ring washer is the OEM one that you’ll remove with the flex plate, but if you want to build this tool beforehand, the 10mm holes are approximately 2-13/16" apart.

10mm = .394", roughly. The crank’s bolt pattern is asymmetric, and I’m not exactly using precision equipment for the hole layout, so I want a nice, loose fit for the draw-in bolts. I used a 27/64" bit (.422"), yielding almost .030" slop. That should be enough :) If your drill index doesn’t include a 27/64" bit, well, 7/16" is only .016" larger, and should be fine.

The result:
The guide ring, the new seal, and the assembled tool

underside of assembled tool

I began by using the long bolts I purchased (and the flat washers to effectively make the bolts shorter), to pull the seal into place. When the long bolts bottomed out in the crankshaft, I switched to the OEM bolts to draw the seal in further. The "throw" of this tool is just a smidge over 1/2", which was enough for the 3.0l seal installation; I assume that the 4.0l seal, which must be pressed in below flush by about .413", might require some careful "finish work" with a suitable punch.

I found that the tool cocked slightly, but that tapping the non-bolt quadrants a bit (that is, the sides of the cap that do not have bolts) corrected that. I also switched the bolts to different holes, which helped.

The finished result:
Installed seal

A $20 tool that did the job for me.

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