Check the oil pressure switch. It's under the manifold between the 2 valve covers. Walt.

Oil leak has been found after driving the car for a few miles. It is coming from the rear main seal.

I'll ask the obvious Q, what type is it and is it new?
F

Frank,
The seal is new,but it is one of those " real deal" neoprene seals that a number of members have used that didn't work. Other members have had success however with the seal. I am one of the unlucky ones.

Bummer. Sorry to hear that. It's expensive and time/effort/patience consuming enough without having to do any of it over again. I feel your pain.
Frank

Those neoprene seals simply LEAK LIKE A SIEVE! I gave up after two tries, and won't use anything but the graphite rope seal from now on. I'm surprised that these are still being sold to Hudson owners, because they don't work at all.

I too have had unfortunate results with these neoprene early Chrysler 318 replacement seals. I know why they sometimes work and why they sometimes don't work......It has to do with the depth of the machined groove in the block and cap for the rear main seal. The tolerances for the old rope seal were much wider than for a neoprene lip type seal, like around +/- 0.020". If the groove is machined on the smaller side of the tolerances used at the factory, then the seal will be "squished" from a slightly elliptical shape ( look at it with the two pieces together, just out of the package) to a round shape as the cap is installed and the cap screws torqued. This squeezes the lip tighter around the shaft for an effective seal. Now if this groove is just about 0.005-0.010" bigger in circumference, the lip will not press on the shaft to effect a good seal. To further compound the problem,the Chrysler crank seal diameter is 2.645". All the Hudson crank seal diameters I have measured are 2.640", so we have 0.005" under right there.....doesn't take much oversize of the groove to cause the seal to fail.

My seal came from Dale Cooper and is the full circle type. It has been completely dry for a couple of years.

"Full-Circle type"? Must be difficult to stretch that guy over the rear flange!
F

I forgot to mention another reason why the two piece neoprene lip seal may not work on the 48-54 blocks.....Many times when these engines are rebuilt, the machine shop "line bores" the block. In a perfect scenario. the line boring is spot-on in the original crank location. However, since the line boring involves "skimming" the caps before bolting them back on and torquing to specs, the exact location of the crank bore can be lost by several thousandths of an inch if the machinist s not diligent. This means the crank will no longer be perfectly concentric with the seal groove. As I stated before, the thick spongy nature of the braided rope type seal is MUCH more forgiving of this. A precision neoprene lip seal is NOT tolerant of this.

Doug, did you make sure the leading edge of the seal faces the engine? When I rebuilt my engine in 1994 I used the Chrysler seal from Dodges, cut off the 2 pieces that stick out the sides and my engine now has 146,000 miles and never had a leak. I corrected one guy that was having an oil leak problem that install the Dodge seal, leading edge was facing the trans and this blows the oil out when running. I've done 2 jobs using Doug's seals and both owners are happy. Walt.

[quote="Frank Hughes" post=17595]"Full-Circle type"? Must be difficult to stretch that guy over the rear flange!
F[/quote

YES,Please, can someone inform me how you get the one piece seal over the crank flange and into the engine, especially with the engine still in the car. Yes, I now the tranny will have to come out. I was a mechanic for 50 years (now retired) and my brain cannot picture this. All th one piece seals I have done were installed into a machined recess in the back of the block and I know the Hudson is not that way. Anyone have a photo of the one piece seal??

Ken, your explanation as to why the neoprene seals won't always work sounds like a right answer to the problem.

Jim,
My comment was more "tongue-in-cheek" than a serious question. I heard what he meant.....unless he thought we were talking about the front seal.
The bottom line on this subject, from my viewpoint, is that it just isn't worth the risk of failure to use a questionable seal in light of the difficulty/expense/frustration involved in the replacement procedure. Some have had success but too many have experienced failure.
Frank out.........