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Oil leak

Hi guys trying to source a slow oil leak (1 drop ever 6 seconds or so) that appears to be coming from rear main. I can see oil marks on front of inspection cover but not on the back of the engine block. I thought rear mains leak down the back of the engine block. Anyway leak is very dark almost black but oil in sump is clean as a whistle, no sign of contaminants. Any ideas? Im stumped by this leak especially why its so different in colour to the rest of the oil. This is a newly rebuilt motor not even a km on it yet. Any help would be great. Thanks

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drain the oil and see if it stops... dead give away. I would say the rear main has not been fitted proper like or else the sump seal is leaking. try nipping up the rear bolts on the sump in case they are loose. it may pay to get some more time on the engine as the seal may bed in. good luck

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Thanks for the advice. I was considering dropping the oil as its over the full mark by about half an inch. I have checked sump seal and there is no weeping but it does look like it has swelled to seal. Im just really curious why the leak is a dark black colour and yet dip stick keeps showing clear oil. And alot of people have been telling me to drive it to allow it to bed in so mabe thats the key. To be patient with the leak and see if it stops over time. Any thoughts on the difference in colour though?

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Been so hot it's just a thought but if really black, could be the windscreen rubber melting.......

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Archie

I can only speculate that as the clean oil is leaking out it is becoming contaminated on the way through - the black neoprene seal ? or other contaminated and not thoroughly clean surfaces. I replaced the rear main seal in my HR 161 engine - I took a lot of time and care and it still leaked afterwards - not as bad though and I have noticed it has got a bit better with time since...I didn't rebuild the engine - I just removed it, cleaned it and replaced all the gaskets/seals/welch plugs etc as it was all original and it looked like a 50 year old engine..the oil in the sump is clean and what leaks out is black...still starts and runs beautifully though

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Andrew

beats me...overfull may be a part of the problem. maybe pull the inspection plate off and look up in there. is that area clean after the reco? behind the flywheel etc?

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Could be gasket seal? If filled before the sealant cures the oil can weep through and contaminate with the sealer to give a darker colour?
Just a thought.

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Info here ...

http://holdenpaedia....

You haven't mentioned whether the car is manual or automatic. There is always the possibility it is a gearbox leak especially if it's an auto because the torque-converter's oil level is so high up and it takes a while to drain out.

Automatic gearbox levels skyrocket after the engine stops because half the torque converter oil drains back into the pan. It's worse if the car is parked facing uphill.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

My mechanic mate is chasing an oil leak at the motor in his EH. He's had the motor out 3 times.
Dave said there is an oil gallery plug at the back of a red 6 and he reckons his might be weeping oil from there.
David

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I checked the back of engine where crankshaft exits and is dry. I drained about a litre of oil out of sump becauseit was over full on dipstick. While under the car i saw an oil leak on the gearbox which travelled to the inspection cover. So i traced the oil leak and found it seeping from the filler plug so i tightened it up. It was the only leak i could trace so perhaps it was that all along. And oil that i drained from the sump was a dark opaque grey while the dip stick was like new oil. So im guessing all the contaminants from running in the engine is dropping to the bottom of the sump.

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The Slipstream can carry oil drops upwards, towards the front of the car, sideways and in almost any direction.

My first port of call with any suspected engine oil leak is the bottom of the oil filter.

Often I've had the O-Ring shrink and create a slight leak there. The slipstream throws that oil every where, in the same way an apparent diff leak can be gearbox or engine.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

if it is gearbox oil you can usually easily tell the difference compared to engine oil. it can also leak out the front of the gearbox and appear like it's from the back of the engine. my rear main with the inspection cover removed appeared dry as a bone as well but it was leaking - with engine running but hardly anything when not. Hopefully it is only the plug as you think.

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Andrew

If the car is a manual, the darkness in the oil might be Asbestos Dust from the clutch plate.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Its a manual and a new clutch kit. I didnt think asbestos was used any more

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Any new Black Paint anywhere?

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Deleted.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

No new black paint. Check for oil leak after leaving it over night and there is 1 drop hanging on bottom of inspection cover near rear main still. No drop marks on floor. Not sure at the moment but oil level has not changed so i suppose it just needs to be driven now as opposed to being started up and checking for leaks.

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I suspect the gearbox Front Bearing Cover.

Check the bolts are tight ...

http://holdenpaedia....

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Im going to retorque the bolts at back of sump and front of gear box just to be sure and possibly rule that out.

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That's a good idea.

It sounds as though the leak is from a location that is still oil soaked when the car and engine have stopped, rather than only when the engine is running or the car is moving.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

I retorqued the bolts which required a little extra tightening before they reached correct torque, so obviously i didnt torque correctly when building the engine or it just needed retorquing afterwards being a cork gasket. Also while retorquing i noticed an oil leak on one of the rear sump bolts. Could be my source with any luck. Anyway time will tell if the leak reappears. Thanks so much for all your help guys, youve been great. Ill keep posted on my progress.

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Those sump bolts don't need much torque, not sure if a torque wrench would be that sensitive, the ones I've used in the past haven't been, maybe better stuff out there now.
They always require a nip up after a bit of use so you've done nothing wrong.

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"It was then I knew I'd had enough, burned my credit card for fuel
Headed out to where the pavement turns to sand...."

Cheers, John

I did see a split in one of these that caused a leak.

On another car the bolts had worked loose.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

car hasn't been driven at all. see first post, so brand new motor. note 4 Belmont. gearbox oil stinks..ya cant miss it

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yes cork gaskets always need nipping up as they settle.

possible other leak points are the rear cam plug and the oil gallery plug.

if its the rear main get under the car with it running and you should see leakage with it running. take a can of brake cleaner with you so you can clean and observe.
i find most "rear main leaks" on built engines are really tappet cover or sump gaskets that need nipping up, or aftermarket chrome tappet covers that NEVER seal properly.

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You said its a newly rebuilt engine while it sounds like you may have found the leak, I wouldn't worry too much about the dark oil colour from the leak.
One thing it may be is cam lube. What sort of cam lube did you use? Last time I used moly lube on a CAM there was a bit of dark residue from the moly grease in the oil for a while its fairly soluble in the oil and it may be what the colour is should disappear after you've run the motor for a while.

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Anthony - Lettuce Alone SS

I didnt think about the cam lube. I used it and an assembly lube. The cam lube came with the cam and cant remember what sort it was. From crow cam. The assembly lube was penrite i think. Also i have just checked the area and cannot see a leak forming. No drops visible any more after about 2 hours of waiting.

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Also small leak from sump plug. Could be using the wrong sort of washer. I think its a fibro washer but i have read your supposed to use an aluminium one. Any thoughts?

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Alloy solved the drip on my VK.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Ok so after leaving it over night i have a small 20 cent sized oil stain. I say stain because it looks dried up. Also a small drop hanging from inspection cover. So it takes more than 2 hours to leak and barely a 20 cent piece dried over night. Not sure if it means leak persisting or if the oil that got sqeezed out during retorquing has just exited. Any way i will get a new washer for my plug as it has a puddle beneath it. Still hasnt affected oil levels though.

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Ok i have fitted the ally washer to the sump and so far no leaks there. Also i found an oil weep around the fuel pump attaching bolts so i pulled them out and fitted them with thread sealer. It would appear that the small weep tracked along the sump and towards the rear. Hopefully it is now fixed.

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I'm glad it's coming right for you.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Good job all. This is what the founders of oh had in mind when starting up forum. Can only imagine the mechanics bill for fixing the oil leak and with a little free advice the problems solved. More of this!

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Archie

I agree its great because hopefully others will read this and avoid head aches from large mechanic bills. A quick update. A small weep is still tracking along the sump line and after 4 hours forms a small droplet which sits under the inspection cover waiting to drop. I have read that small weeps like this can take time to stop weeping after its fixed. Kind of like how after a wound is stitched up it can still weep for a time. But i have cleaned the whole sump line it was tracking and after 4 hours it weeps a little. Fairly sure this was the issue and it wasnt the rear main. I will be driving it on the road once i get a permit. Basically i wanted to let every one know my oil leak came from the fuel pump attaching bolts and was fixed with a little thread sealant. If any one reads this with a similar problem, check your sump lines. If the leak is small enough it can track all the way along the sump line as opposed to spilling over the sump line. I hope others benefit from this and thanks again to every one who offered help.

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Just as you say, OH members sharing their experiences creates a pool of priceless info that can benefit others.

As you've shown, sharing the repair gets a lot of minds working.

When the sheds come back, please create a shed and add lots of photos of your car and work. I'd love to see them.

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T

My Shed

Holdenpaedia, they're the brakes Mate.

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