427 Oil Leak Mystery

Paul Sutphen · #1 (**permalink**) 10-25-2003, 07:23 PM

My friend (Dave) and I worked all day on his Cobra chasing a mystery oil leak. Oil in significant quantity (enough to leave a 3" spill on floor after 15 min. run) is leaking at the joint where the Lakewood housing plate and the block where the pan is, come together, just in front of the oil pan flange. We changed the main rear seal (both circular seal and vertical seals), removed the tranny and flywheel, replaced a suspected leaking oil plug in the back of the block, replaced the oil pan and gaskets too! We didn't find much if any oil on back of engine block behind flywheel although the clutch housing had been soaked with oil as a result of the oil leaking down the plate and into the holes in the front of the lakewood plate. We changed the clutch pressure plate. We reassembled thinking we had covered all the bases, test ran with car on lift, and about 2 minutes after starting engine, oil resumed leaking - just as heavy as before. There are no oil leaks up above around valve covers and manifold joint. No oil is leaking into clutch housing as we taped off the holes in the Lakewood bell housing. We are now suspecting a cracked rear main bearing cap that leaks toward the rear between the bell housing plate or something else very unusual. Before we drop the pan again, do you have any suggestions?

Paul Sutphen and Dave Betts

Doc_Naughty · #2 (**permalink**) 10-25-2003, 08:30 PM

Just out of curiousity, where did you get the 427 block?

If it came out of a race boat or actually the crank came out of a reverse rotation boat motor, they were built to spin in reverse.

If you install a reverse rotation crank and spin it in the normal rotation, the little groves on the rear crank seal surface will pump oil toward the seal and flood it causing a leak. Normally the machined grooves are designed to pump oil away from the seal.

Laying on you back, looking up at the rear main seal surface of the crank, the crank spins left to right (counter-clockwise).

The grooves should look like back-slashes ( \ \ \ \ \ \ \ ). If they are going the other way, oil will be pumped toward the seal. Also, are you installing the seal with the lip in or out? Out is wrong! The lip should face in toward the crank. Incorrectly installed and the internal pressure of the engine will blow oil out the rear.

Doc

PatBuckley · #3 (**permalink**) 10-25-2003, 10:11 PM

I would check to see that the intake manifold isn't leaking.

Brent Mills · #4 (**permalink**) 10-26-2003, 01:41 AM

I had a nasty leak which I suspected to be the seals because it leaks soo much (similar to your experience).....Pulled the pan for a 3rd time and made absolutely certain that the pan rails were straight.....Didn't use any gasket goop this time either (did use the spray sealant), slapped it back on and all was good!

427 S/O · #5 (**permalink**) 10-26-2003, 02:43 AM

Paul, a few years back I accidently picked up and installed a stright plug for the main oil galley right above the oil relief valve, I thought it was the main seal
leak. Just something to consider.

ed cougar · #6 (**permalink**) 10-26-2003, 04:55 AM

I had that same pesky leak it would leave about a 3" puddle on the floor it was dripping from the flwheel inspection cover motor side, I never did find where it was coming from, it mysteriously just stopped leaking, the motor was just run-in after a rebuild and I think the rear seal may have needed time to swell up or something? Anyhow it totally stopped leaking after a few trips out.

Cracker · #7 (**permalink**) 10-26-2003, 05:22 AM

At the bottom/back of block there are two holes that need to be plugged. There are supposed to be to rubber plugs that go in them but they never stay in. I use a little gasket maker to plug them and have since never experienced any further leaking.

Paul Sutphen · #8 (**permalink**) 10-26-2003, 05:53 AM

Thanks for the replies. Doc., you may be on to something. We will check with the engine builder but from what we know, the block and crank originated from auto application. Pat and Brent, those areas were the first we suspected and have ruled them out. We even used a flourscent tracer and black light previously and may well have to do that again. Ed, this leak has existed for a half year, the car is undriveable unless you want to bolt a diaper under engine! No sign of improvement with time.
Paul

mr0077 · #9 (**permalink**) 10-26-2003, 06:48 AM

Just another pesky problem to toss out...the front machine plug (on sideoilers only) can leak and drool down the front of the block, run back to the rear on the driver's side of the pan rail and around the back of the pan, then dribble out on the floor...makes you think it is a leak at the rear of the motor.
Let us know what you find.

ERA649 · #10 (**permalink**) 10-26-2003, 01:58 PM

Paul,
What did John say? I have and oil leak too. Just like you describe, I thought it was my valve cover on the left side but now I'am not sure. I have a 428 for the record.
Let me know what you find.
Also you and Dave should come the day after thankgiving for the cruise.

Mike W.

RICK LAKE · #11 (**permalink**) 10-26-2003, 03:19 PM

Paul Sutphen Hi Paul Befor you go crazy, do youself a favor. Go to the GM dealership that is closest to you and buy a bottle of engine leak dye and put in the motor and run it for a couple of minutes and wait for the leak. Than get a black light bulb, put in a drop light and look for the leak. Don't pull anything apart. Clean the motor off befor you do this. Follow the stain and you will find the leak. Good luck Call me If I can Help after 7:00pm 732-254-3536 Rick Lake

Paul Sutphen · #12 (**permalink**) 10-26-2003, 04:47 PM

Mike,
John is scratching his head. Have you discussed your problem with him? Thanks to gravity, there's a good chance your oil leak is coming from above -either the valve covers or perhaps from the intake manifold joint. The rear main seal can improve with time. It took me awhile to "conquer" the problem. Still keep cardboard under car.
Paul

Doc_Naughty · #13 (**permalink**) 10-26-2003, 10:07 PM

Doc here again . . .
What type of manifold are you running? Some of the early type manifolds with the breather at the back for crankcase ventilation were known for leaking oil but usually only if the engine was developing high pressure internally. Make sure your crankcase is running under vacuum, not pressure. Improper crankcase ventilation will cause excessive presure and oil will leak out of all your seals.

Also, have you checked the transmission front seal for the input shaft or is it definately an engine oil leak?

Doc

coosawjack · #14 (**permalink**) 10-27-2003, 04:31 AM

Hey Paul...

I had the same kind of leak with my 408W stroker in a 1974 (rope seal) block!!

I pulled the pan and replaced the two piece neoprene replacement seal 4 times with no luck and even pulled the engine to try a ROPE SEAL.....BAD IDEA!!!

Came to discover that in older blocks the rope groove was not very precise and some blocks wouldn't squeeze the two piece seal quite enough to seal on the crank!!

Found a sleeve kit (Fel-Pro "Ready Sleeve") and installed it on the rear seal crank journal and...VOILA!! NO MORE LEAK!!!

BTW, you can install it without pulling the engine!!

It increases the journal diameter by .009" and if you can find one for your crank it will GUARANTEE that you have no rear seal leaks!!

Good Luck,
Jack

Paul Sutphen · #15 (**permalink**) 10-27-2003, 07:13 AM

Doc-
The engine has a 2x4 Blue Thunder manifold with a breather in the back and an oil filler cap in the front. Also, Dave has a breather on each valve cover so not much pressure if any is internal but certainly there's no vacuum either.
Jack-
The seals are the new neoprene formed seals and they were replaced. It seems as though oil is originating from the void between the back of the engine and the bell housing plate. I don't think the oil is getting into the flywheel side of the plate because no oil is seen coming out of the vertical joint where the plate and the bell bolt up.
Our plan will be to probably pressurize the oil system but not run the engine with flywheel removed. This should tell us whether or not the seal is the culprit, or some other area is leaking under pressure, such as a hairline crack in the casting around say an oil plug or something out of the ordinary.
Dave and I certainly appreciate all your help with this and we'll keep you informed as we move forward.
Paul and Dave

Paul Sutphen · #16 (**permalink**) 10-27-2003, 03:09 PM

Guys,
Has anyone ever seen a small groove milled into the back of the rear main lower half-as though it was supposed to carry away oil leakage past the seal? Oil comes down out of this groove on Dave's 427. Latest plan, run engine, block off all air vents and put shop vac. vacuum on oil galleries, etc. to see if seal leak stops. Nothing ventured nothing gained!
Paul

Doc_Naughty · #17 (**permalink**) 10-28-2003, 09:27 PM

Paul and Dave,

Read the post above . . . what "Coosawjack" is saying could quite possibly be the answer. Early blocks were known for variations in casting and machining processes, therefor, rope seals are the only way to go cuz the neoprene ones depend on the block being precise . . . Rope will conform to just about any irregularity and once it swells from the oil, will seal perfectly. I've built both normal and reverse rotation engines and always went with the rope for early blocks. They do cause more drag on the crank but with a 427 as the source of power, who cares? :>)

Doc

Keithc8 · #18 (**permalink**) 10-28-2003, 10:07 PM

We have always had a oil leak problem with the sticks that are sent to go down the side of the cap. Some of the blocks because of age and being run hard over the years do not fit as percise as they once did. We use the cheese wiz style canister of silicone. we leave out the sticks and fill this void with silicone all the way done. we pressurize this area with the can untill we silicone coming out from the cracks between the cap and block all the way up. We then wipe it even with the cap. We also put a small bead between the cap and the block at the main saddle. We will also turn the seal a small amount out of the block and the cap so there is no crack where the cap meets the block. This is just what we have had the best luck with. Good luck, you got love this stuff why else would we go through so much greif.

Paul Sutphen · #19 (**permalink**) 10-29-2003, 07:26 AM

Doc and Keith,
You both have been most helpful and we will be guided by your suggestions and ideas. I think this is a '64 center oiler block and may well have inconsistencies in the alignment of seal to journal. We still have the FelPro circular and straight seals installed. The seals we pulled out, look almost new as though there's little contact with the seal surface. Last night, Dave and I plugged all openings and stuck the shop vac on the oil fill tube and pulled 3.7" vacuum. The maximum the shop vac could produce before the hook-up was 3.8". This would indicate to us that there was very little air leakage into engine cavity. Anyway, we started motor and watched for leakage. After quite some time, we observed leakage - about 50% less than w/o the vacuum applied.
We are perplexed as to go with FelPro Sleeve and new FelPro seal or go to rope??? We also may try a PVC hook-up. Both may be half fixes but can be done w/o pulling motor and allow Dave some leak-free driving of his Cobra. Thanks again.
Paul

STARLINER · #20 (**permalink**) 11-03-2003, 06:04 PM

Hello Paul, I've been thinking about your mystery oil leak. As I'm sure you are well aware, the 427's were not pampered engines to say the least! If you don't have knowedge of the paticular past history of the motor, one may safely assume the worst and work from there. Your friends problem ,However, seems to reflect a problem that a close friend of mine, an FE- expert and pro-drag race engine builder/ Ford consultant , (who has worked with the design of the FE motor from its beginning ), Is quite certain that this is damage( posisible warpage, and or cracking in the main bearing cap and surounding area) Due to severe over heating! There is no quick fix for this problem if infact the motor has been overheated to this point. These are not easy problems to detect by the naked eye, and usualy require extensive magnafluxing, pressure testing of the oil system,and verifying that the block and its main bores are straight. Has the motor been over heated to your knowledge??? How are the main bearings looking?? Any signs of coper showing? This could be the first signs of the main problem, causing your symtems. There have been quite a few good deals on some good slightly over bored blocks,and NOS blocks on E-bay and the like lately. The 427 shelby block is pretty hard to beat too! It's all aluminum, and very repairable if necessary!Before you go and spend a lot of time and money, consider another block while the pickings are pretty good. good luck, hope this helps determine the source of problem. STARLINER.



FE Forums sponsored by Keith Craft Inc.