How Can You Tell The Difference Between an Oil Pan Lower Gasket Leak and a Rear Main Seal Leak?

[redhill]

Hi all,

I hope everyone's ST is running better than mine ;]

Hoping for any insight as to diagnosing an oil leak. It's mostly at the base of the oil pan and some is getting on the differential cover.

I've been told it's either the rear main seal or the lower oil pan gasket but I'm trying to find out which it is before I go much further. I'm thinking of replacing the lower gasket myself and then getting an oil change and having the shop put a quart of Lucas Engine Oil Stop Leak in. I had luck with this product stopping a leak in my rear differential...

Do you guys think this is the best approach? There's no way I can afford to replace the rear main seal (with all the labor involved) so I have to do the best I can myself...

A few pictures are attached which I hope will help.

Thanks in advance for any insight as I need to keep this truck on the road!

 

[boominXplorer]

Post a pic of the back corners of valve covers. It's the most common area to leak. It will run down the back and look like a rear main leak.

 

[redhill]

Post a pic of the back corners of valve covers. It's the most common area to leak. It will run down the back and look like a rear main leak.

Thanks for the reply. I hate to sound foolish but where are those, exactly? I've changed out starters and batteries and done other light work but I'm not an overly mechanical guy...

 

[redhill]

I should also say that the oil was overfull (by a quart) but there's a lot of conflicting thoughts online about whether or not that can or will cause a leak...

 

[boominXplorer]

The thing your oil cap screws into is the valve cover. Depending on year of sport trac they will either be aluminum or black plastic.

 

[redhill]

The thing your oil cap screws into is the valve cover. Depending on year of sport trac they will either be aluminum or black plastic.

I just took it to Advance Auto and walked through it with the guy. There's no way to get my cell phone behind to get those pictures but there is definitely no leak coming from where the head meets the valve cover anywhere...

 

[koda2000]

I think your question should be, how can I tell if my valve cover gaskets are leaking? When they leak guess where the oil shows up. The 4.0L SOHC engine tends to be pretty good about not leaking oil, except from the valve cover gaskets. My '01 Job 2 engine leaked oil pretty bad at 184k. Replacing the valve cover gaskets stopped nearly 100% of the leaking. Not an easy job to do, but doable.

 

[N2FORD]

I have also had a oil filter housing o-ring leak, it ran down the back of the block onto the oil pan and kinda hard to tell where it came from.

 

[redhill]

So how did you guys wind up finding the source of the leak? I can't see anything coming from the valve cover...

 

[koda2000]

I had removed my plastic inner fenders to change my spark plugs. It was obvious that the source of my leak was coming from the valve covers. The gaskets (which are kinda like huge o-rings) become brittle with age, shrink and even crack. They came out in many pieces.

 

[sr139fox]

Replaced my oil pan gasket. Still had leak. Turned out the right valve cover gasket was leaking. Clean the motor real good. Drive some then look for the source of the oil leak. Dave P.