Engine gurus, oil leak question.

Maxum96 · 11-16-2009, 09:32 PM

On my new 393 Windsor i'm getting an oil leak at the back of the block. Oil is dripping down the front of the flywheel shield. My question is this, the oil is black like old diesel engine oil. Any ideas where it's leaking from? I don't think the pan gasket is leaking. If it was I would expect to see clean oil. Would the black oil be indicative of a rear main leak? I can't remember at the moment, but aren't there oil galley passage plugs behind the flywheel? If so, I'm wondering if there's no thread sealant and it's leaking oil. There was no thread sealant on a water passage plug that was leaking on the right side of the block.

rc4mike · 11-16-2009, 09:39 PM

i had the same leak on my re-built 408w. I swore it was rear main seal or pan leak at the rear. Changed pan gasket several times...still leaked. Then realized i had a late model pan gasket on my early model pan...but still leaking. Then i found oil at back of one valve cover. It was leaking down the back, into bellhousing and then down to bottom of clutch cover. Tightened the valve covers and no more leaks. Frustrating!!

crickifur · 11-16-2009, 09:50 PM

That makes a lot of sense!! A lot of times when your trying to diagnose a leak back there it can be the smallest of things. My advise to you, to make sure you get it the first time is to drop the pan and inspection cover, this will allow you to check the pan gasket and the bottom of the block to ensure the gasket was fully sealed (you should be able to see the contact marks from the seal and/or silicone if you used any). On a lot of cars, you can change the rear main quite easily. Just tap it out around the crank using a plastic hammer and a small punch. Once you can grab the rubber seal with a pair of pliars, lightly pull till it pops out. lube up the new seal and install it in the opposite matter. The good new is that they arent expensive just time consuming to install. Put your new gasket on the pan and bolt up the pan being sure to PROPERLY TORQUE it. The problem with head gaskets and valve cover gaskets is that it is almost impossible to see without being able to stick the vehicle on a lift.

Your other option is to go to advance auto and get a bottle of ultra violet dye. They sell a goggle, flashlight combo for $20. Add the dye, drop the access cover.crawl under the car, turn on the flashlight, put on the glassses and where you see bright green, you have a leak

! It screams at you and it is WELL worth the $30 you will spend when you compare all the lost time from trying to find it and the money in gaskets and seals you will spend till you find the right one.......

Maxum96 · 11-16-2009, 09:50 PM

I'm 100% certain that is not the valve covers nor the intake manifold that is leaking. My hood is not on and I can clearly see all around the heads and back of the intake. I've even run my hand around it. It is definitely coming from the area around the rear main. I'm running a Lakewood scatter shield and there is no inspection cover to remove so I can look in there. The think that's really got me going is the color of the oil that leaking. It's black as black can be. Whenever I've had a leaky pan or other place, the oil was the same color as what the oil in the pan was.

crickifur · 11-16-2009, 10:29 PM

yeah but oil turns black quicker than you may think. The more miles on an engine, the more carbon, thatll blacken your oil a little, some of your old oil is still there, thatll blacken it a little. Does the oil have a burnt smell to it?? are you noticing any oil loss or blue exhaust smoke? Bad oil control/compression rings will assist in making oil black quicker as well. Either way if you are getting oil there, you have a leak somewhere in there, your gonna have to drop the parts out of the way to get in there......

Maxum96 · 11-16-2009, 10:38 PM

It's a brand new engine. The only part that was rebuilt and reused was the block. All top of the line high dollar parts inside and out. The oil is being blackened as it leaks out. I'm hoping the discoloring of the oil is a tip as to the source of the leak.

crickifur · 11-16-2009, 11:20 PM

hmmmm I cant think of anything around the flywheel that would cause it to go black unless it got REALLY dirty in there prior to the leak starting , but even then i dont think it would be dirty enough in there to blacken oil, just maybe add some debris...

camachinist · 11-17-2009, 01:13 AM

What kind of assembly lube did you use?

There's the rear cam soft plug and the three oil gallery screw in plugs back in the area of the flywheel/flexplate/blockplate.

frdnut · 11-17-2009, 01:18 AM

I had the same type problem and it took a while to figure it out..In my case the rear journal that the oil seal rides on was undersized from Scat...I tried everything to make it stop and it didn't..Finally tore down the engine and had the crank measured and discovered the problem..Had the journal built up and it fixed the problem...I truely hope this is not the case with your engine

6t9mach1 · 11-17-2009, 12:46 PM

Quote:

What kind of assembly lube did you use?

Yeah that was kind of what I was thinking. If its not the valve covers there are only a few things it could be; intake gasket leak, rear main seal leak, or a leaky cam plug or oil galley plug. Ah the joys of a new motor

Maxum96 · 11-17-2009, 12:50 PM

I used moly lube in a few places. When I had the machine shop do the repairs after my recent nut down the motor episode, I had them reassemble the short block. I'm going to call them to see what they might think it is. I might just end up pulling the trans, scattershield, and flywheel off and see what's leaking that way. Luckily the TKO is pretty easy to pull out.

crickifur · 11-17-2009, 01:46 PM

wow man that really sux!! Thats such a beautiful engine. Did you powder coat or is that blue engine paint??

Maxum96 · 11-17-2009, 03:13 PM

Quote:

Originally Posted by crickifur

wow man that really sux!! Thats such a beautiful engine. Did you powder coat or is that blue engine paint??

Thanks. It's rattle can engine paint. I talked to my machinist today. He feels that the black in the oil is rubber particles from the rear main seal. He said they've recently had some problems with Felpro rear main seals. He said he's tried other brands, but when he opens the package they all have the same number indicating they're all made by Felpro.

6t9mach1 · 11-17-2009, 03:47 PM

Thats too bad. All the headaches for a $8 part

crickifur · 11-17-2009, 03:51 PM

Yeah no kidding

! So basically what he is saying is that the felpro gaskets are breaking down

What a freakin disaster