Hey guys,

I took off my oil pump and found a horrible crack on the rear main bearing cap. I need advice. Do I need to replace it or can if function with this amazingly convenient crack? Am I correct that if I have to replace it, it's a full kit and It would have to be machined to fit? What could have caused the crack? Old age? The truck has almost 150K on it. I posted the images below. You guys always save my ***. Thanks in advanced!!

 

to me it looks like a porosity hole in the casting, and it would have been there since day 1. i'm very surprised it didn't get tossed out during the QA checks that go with the machining of the cap and then again at the assembly of the motor.

but - its actually not under the bearing race and its not in the seal cavity. if there's no evidence that its new damage (debris), and if it retorques correctly without any further crack or breakage, i think i'd just put it back together and drive on.

do replace the rear main seal.

 

Are you referring to the hole between the pump mounting face, and the groove for the oil pan seal? If so, that is supposed to be there.... basically, its an oil drain.

 

+1 - all I see as a crack is the oil drainback slot, which is the way the cap came from the factory and is just fine. Can you please edit and re-post your picture using the something like the paintbrush program to circle (in red) where the crack is that you are concerned about, so that we are all looking at the same crack?

 

thanks guys! Sorry Here are better photos. Just to confirm.

 

Yup - oil drainback slot - wouldn't hurt to clearance it a bit/knock down some of the casting slag with a Dremel tool to clean it up a bit, but looks normal to me..

 

Seconded. That's normal. Also second cleaning up some of the casting flash.....

 

An update for you guys. I replace the rear main seal and oil pump. I also used a felpro gasket for the pan and install a new Dorman pan. Yet I still have a leak in the same area. The gasket was lined up with the holes. Is there a pattern I'm suppose to use when installing the pan? I'm just going to take it to get fixed. I have had it with this truck..

 

The pattern as with anything on a vehicle and rule of thumb, always work your way out from the center to the end in an X or cross pattern. Permatex works wonders in areas that aren't perfectly flat, generally its wise to dab some on the ends of the oil pan by the timing cover and rear of the pan where the rubber gaskets end that seal the pan from the crank shaft as well as in the front where the timing cover meets up.

 

rydog2624, we started with a possibly cracked rear main cap and now we are talking about an oil pan or rear main seal leak. Can you please provide more details, such as where the leak is occurring? If possible, pictures that show the leaking area would be helpful, too. I certainly understand how frustrating it is to perform a repair and the repair not work out as desired - been there many times, however, sharing all the details about the issue(s) on forum(s) usually provides good feedback for a plan to solve the issue. :-)