I need some help identifying the oil leak in my motor. It is a 1970 429 motor out of an LTD. I have an oil leak at the back of the motor that I thought may be a rear main seal.

I removed the oil pan and it seems like it is the pan gasket from what I can tell. I see no oil at the flex plate only at the pan gasket. (I'm assuming there would be oil on the flex plate if the seal was leaking)

Is there a way to determine which it is, the seal or the gasket?

Rear gasket:


No oil on the flex plate or in the bottom of the housing:

 

Look at the pan seal, it obviously looks like wrong. I would say that is your problem.

 

Other causes of oil leaks at the back of the "385" series engines is the oil pressure sender, which is right behind the intake manifold, the rear seal of the intake manifold, and valve covers. Oil runs down from any or all of these areas and appears like it could be coming from the pan or main seal. Not saying it is, just something else to check.

 

Thanks guys. Yeah, I checked and there is no oil coming from the top of the motor. Valve covers and oil pressure sender intake, all dry.

I see what youre saying truckeemtnfords, that seal looks like its folded over on itself.

 

I could see something wrong but was not quite sure in the photo what it was. If it is folded over that definitely would cause you problems.

 

I wanted to make sure it wasn't the rear main seal before I put it all back together but that gasket does seem to be the real problem.

I am going to replace the pan too, its pretty beat up. I don't know much about pans so I am going to start a new thread about select one... after I search.

 

Most auto parts stores sell small bottles of UV dye. Then all you need is a cheap blacklight bulb to put in your shop light. This helps trace the source of your leak. It is particularly useful finding pinholes in castings like engine blocks but it works well for all oil leaks.

 

The UV dye would have been a good idea but I took it all apart already. I will have to keep that in mind if I get another leak... lets hope I never need it.

 

So now that I have it all apart and cleaned up, I'm trying to decide if I should just change the rear main seal anyway.

It doesn't look like there's oil behind it. I don't know of a way to be sure it's bad but if I don't change it and it leaks after, I will have to do it all again!

I know, this seams like a therapy session but I am looking for opinions... this is what t looks like now.

 

I don't see any signs of oil behind it, except what would have come from the pan seal. There is a lot of extra work to replace the rear main correctly so only you can determine if that is something you want to tackle now. Prime driving season right now for most us so I would throw it back together and drive it. If it leaks put "mechanic in a can" in the engine and wait until cooler weather to pull it apart, but then again you are in AZ which is always prime driving season unless you are in the mts like Flagstaff.

 

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Bill, I think you posted to the wrong thread, this one is about an engine oil leak at the rear of the engine.

 

I posted in the correct thread, but...

The post has gone bye bye now...