65tripleblack

I have a 327 Chevy and have been fighting an oil leak for many, many years. I have finally given up and let it be. There is always some oil on the drip pan and most of it is coming from the left side. The drip is always present on the oil fill plug on the pan, and the entire chassis rearward from there is oily, including underbody, crossmember, the transmission, etc.

Again, I have given up on fixing it. Have changed the rear main seal twice and gone with a one piece oil pan gasket.

Can this leak get into the bellhousing and cause the clutch to slip?

Has anyone found a way to seal the bellhousing from the engine block to keep iol out of the clutch?

Is there a possibility that the distributor gasket is leaking? The breather tube on the back of the block?

Again...........I quit trying to find the oil leak...................it has been 15 years of unsuccessful. How can I keep the oil out of the clutch?

Bluestripe67

How old are all the gaskets? Too old, replace them. Were the oil pan bolt holes dimpled? If so and you didn't correct it, you may not be getting as good a seal as possible. I don't know about sealing the bellhousing. Breather tube and dizzy gasket are easy fixes. If you didn't offset the new rear main seal, that, and any pan gasket leakage will contribute to drips/drops. I am convinced that what you described is normal, and I call it "oil vapor misting". Any small drip/drop gets misted by the air flow under the car and after a while, the accumulation looks like a coating on everything. How sure are you that the clutch disc is contaminated? Dennis

Westlotorn

I hate Oil Leaks and the mess they make. I spent about 70 hours at Christmas fixing my Wife's BMW X5 V-8 that was leaking oil. That damn car has a high pressure oil port sealed by an oring hidden behind the Alternator, Power Steering and Motor Mount. $6 part and 17 hours to fix. Then I got to do the Intake manifold, Valve Covers and the Variable Valve timing Seals and Front Timing Covers to finally seal that bugger so it has no leaks. Any Oil Leak can be fixed, the worst part is going to do a small job and everything is a mess from the leak as you described making you a mess as you try and fix a small job.
You spin your 327 very high, a stock rear main seal will leak for sure if you rev over 6,000 RPM. High RPM equals high heat on the rear main seal and stock seals will cook and fail. You can buy the performance seal which handles the heat associated with the high rpm shaft speeds.
A leaking rear main seal usually drips down and never hits the clutch.
A leak from the intake manifold at the China wall or your distributor or vent tube and valve covers are all high enough to possibly enter your clutch area.
Oil does not drip up, always down so take a black light in the dark and search for the start of the oil trail. The oil, at least the standard oils I use will glow purple in the light if the block is clean and you can find the start of your leak.

wmf62

I would say that the odds of oil getting on your clutch is between slim & none...

first line of protection is the flywheel keeping it on the engine side of the clutch, second is the centrifugal force of flywheel the slinging it off. it would have to be a gross leak to eddy around inside the bellhousing, BUT make sure the tin 'inspection cover' is in place in order to add a barrier to blown-in oil.

Bill

Frankie the Fink

and I'll bet one helluva lot of rear main seals are changed because of valve cover leaks

HilltopClassicCars

Another potential oil leak source is at the rear of a small block the 1/8" pipe thread hole for the oil pressure sending unit or oil pressure line. Make sure the sending unit or oil line connections are tight and not leaking. I agree, valve covers are a very common source as is the fuel pump rod locking bolt hole at the front of the block. If a short bolt with thread sealer is not in that hole after the temporary longer holding bolt is used during a fuel pump replacement, it will eventually start leaking and travel back. I've seen situations where the short bolt was not replaced or not sealed and the engine ran sometimes for years without pushing any oil out and then way day, for no apparent reason, oil starts finding it's way out.

There are fairly inexpensive kits with dye that you add to your oil then use a UV light with glasses included in the kit to more easily find an oil leak source, but you must wash the entire area clean of any oil before using to produce best results.

DansYellow66

If oil is catching on your pan drain plug I would say that is not from your rear seal but something directly above and/or forward of it. Your best bet may be to clean everything up thoroughly and get some leak detector UV dye from a parts store and add to your oil. That should give you a pretty good path to follow to the source.

65tripleblack

Gaskets have been replaced over the years and leaked when brand new. Leak quantity is always the same over all these years. Yes every time I remove the pan I flatten the sealing flange to remove any dimples. Clutch always looked dry, except for this time the fingers have oil on them.

This time the diaphragm spring fingers had oil on them. That might be due to the fact that the next to last time I had the car out before laying it up for the winter I had the RPM's up for an extended time. Never had the engine scream like that for a prolonged period. The engine sputtered but didn't die and smoked. Drove it home and found oil everywhere. It came up through the breather tube and flooded the carburetor, dripped all over the intake manifold and down covered the bellhousing. Looks like at least 1 maybe 2 quarts were sucked up the breather and into the air cleaner. After cleaning everything, adding oil, replacing the air filter and driving for a few days, the engine runs as normal.

65tripleblack

I replaced both times using FelPro red (fluoroelastomer) seals. Offset from parting line.

65tripleblack

I've done all that time and time again over the years. Insanity is doing the same thing over and over and expecting different results..........I quit a few years ago. As long as the clutch is dry then I can live with it. Checked and replaced gaskets and seals from timing cover, to fuel pump, to fuel pump steel cover to engine block, valve cover gaskets, intake gaskets, Right Stuff on China walls, rear main seal, dye and UV light, etc.

DansYellow66

The dye and UV light didn't turn up any smoking gun leak trails?

I think about the only engine leak that might compromise a clutch is a loose rear cam freeze plug or a really loose or fallen out oil gallery plug. Had the loose cam plug happen once myself and even that didn't get to the clutch - and I never had to bother with undercoating the chassis after that. Otherwise probably not much chance of contaminating the clutch.

wmf62

IF the transmission is a Muncie, the only real risk to 'oil' on the clutch assembly is if the transmission should somehow get overfilled/overflow as there is no front seal on a Muncie

Bill

65tripleblack

The oil gallery plugs are threaded and plugged with flat head square drive pipe plugs. The cam plug looked OK, but I replaced it anyway......probably about 10 years ago.

No smoking gun trails. So maybe it IS the rear seal.

I spoke to a FelPro tech yesterday afternoon and he told me something that I never realized: if the crank journals were align bored........as mine were.....then I should have measured the rear main diameter. SOMETIMES but not always, it will need an oversized seal if it measures bigger than 2.8406".

One other thing is that there is a small imperfection on the sealing surface of the crank. I can catch my nail on it. I have tried to polish it out with emery and it's not easy getting to it. It acts more like a crack than a gouge because it is very thin and looks jagged. It also doesn't go away with emery..............and I did this both times I was in there. But I don't think it can be a crack. There's a LOT of torque going thru there.

I can also see if an offset seal (FelPro: BS11829-1) lands on fresh steel.

If you read the last paragraph of post #8, I'm confident that that explains the oil on the PP fingers this time around. I know why that oil came up the breather, and don't normally put the engine thru a duty cycle as severe as I did last winter to cause the event. I flooded the lifter valley is what I did, and I know the reason for the overflow.

65tripleblack

It's not a Muncie...............it's a Borg Warner T45 (RS600-Kiesler)

wmf62

thanks...

Bill

Westlotorn

"One other thing is that there is a small imperfection on the sealing surface of the crank. I can catch my nail on it. I have tried to polish it out with emery and it's not easy getting to it. It acts more like a crack than a gouge because it is very thin and looks jagged. It also doesn't go away with emery..............and I did this both times I was in there. But I don't think it can be a crack. There's a LOT of torque going through there."

I think you identified your problem. Point contact rear main seals need a perfect surface because your oil stop is like the point on a V all the pressure is on that point to stop your leak. Any scratch or imperfection will allow oil to get past the seal.
Fill the scratch with JB Weld and smooth it with Emory cloth down to about a 600 grit surface. Any low spot from contact damage will normally also have a high spot associated with it. File down the high spot before the JB Weld is applied.
The right way obviously would be to pull the crank and have it polished down.
If an offset seal will get you off the bad spot that is even better.

65tripleblack

Thanks.
It is very thin and catches my fingernail. It's odd that such a shallow imperfection doesn't sand out after two extended tries with emery. It doesn't seem to respond to the abrasive, and the crank was polished just before the engine was built.
If it's a crack then the pressurized oil is traveling thru it and past the seal. But, it sounds impossible to have a cracked crankshaft and not break it in half with all that torque.
If it's a shallow "crack", then the oil will migrate thru unless the offset on the offset seal is to the inside (forward) of the "crack".

wmf62

'crack' is a scary term (and not in the drug sense...) as cracks propagate in stress/vibration environments like a crankshaft and usually lead to a catastrophic failure. scratches or gouges, although they can present stress risers, not so much...


Bill

tbarb

Could it be the high volume oil pump or the stock PCV set up.

65tripleblack

What are you referring to.