Rear Main Cap with attached pipe

rgmutchler · Post by **rgmutchler** » Mon Jun 13, 2022 7:05 pm

I took my engine out for some different maintenance items including a rear main leak. I noticed that in some pictures I ran across on the web there was a short pipe coming down out of the rear main cap. The below picture is one I saw.

The following picture shows my rear main without the pipe, but a hole in the cap for it.

Most of the pictures on the web that have the pipe coming off the rear main cap seem to be Model B and GPW engines or engines with a timing chain. I don't know if that means anything.
My engine has been running well and has good oil pressure but I am concerned about not having the pipe or tubing coming out of the hole in the rear main protruding down into the oil pan.

Any info would be appreciated.
Ralph

Post by **wesk** » Mon Jun 13, 2022 8:08 pm

I believe you will find that the early MB/GPW engine had the drain tube for the rear seal cavity attached at the rear main and the later engines eliminated the use of the drain tube but retained the drain hole in the cap.

Corrected 2149 6-13-22

rgmutchler · Post by **rgmutchler** » Mon Jun 13, 2022 8:20 pm

So it is not an issue as the oil pickup is now where the blue gasket is on my engine by the middle main.
Thanks Wes, I just happened to see some pictures and saw the tubing and couldn't find any pictures in the manuals, military or civilian of the rear main cap itself.
Ralph

Post by **wesk** » Mon Jun 13, 2022 8:47 pm

The rear main of the WWII engine is shown in TM 9-1803A page 20. It is also clearly shown on page 26 & 27 of TM 10-1186 dated Jul 1, 43 MA/MB Master parts list and pages 11 & 12 in the ORD 9 SNL G-503 dated OCT 49. All these show the purpose of the hole with tube is to drain the seal cavity.

For the M38 L134 the TM 9-1804A page 87 has a very poor illustration of the rear main cap but you will find a split illustration on page 115 that shows the purpose of the hole in your photo is to drain the seal cavity. The photo on page 51 shows the main bearing caps in blowup format. The M38 ORD 9 SNL G-740 on page 13 shows the drain function of the hole as well.

rgmutchler · Post by **rgmutchler** » Mon Jun 13, 2022 9:03 pm

Thanks

Post by **wesk** » Mon Jun 13, 2022 9:15 pm

Here's the illustration from the CJ manual SM-1002-R5 1965: