Mk3 massive oil spill

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hillbone

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Hi All.
Before I start tearing the bike apart I though I may ask for some preliminary thoughts.
History.A few months ago I replaced my oil pump sealing washer with the correct new one. I also discovered the anti drain valve plunger in the timing cover on my Mk 3 was stuck in the chamber so I replaced it and the spring.
I also noted that the oil pressure relief valve washers were missing so I installed the recommended amount as per manuals.
Upon running the bike with 50 weight oil as always I noticed that when hot, the oil pressure on my trusty Old Britts gauge, had improved from 10 lbs to around 35lbs. Wierdly enough, when firing the bike up the gauge shows 100lbs ( off the scale ) then settles back when warm to 35lbs.
I have now just returned home from 6 weeks away and the garage floor looks like an Exxon Valdez crash.
So, can any one make a guess or an informed reason where this oil has spilled from? Where is the leak?
I havent found it yet and why so much all of a sudden?
Has the 100lbs burst a seal somewhere and where would the exterior leak be?
Any info before a tear down would be appreciated.
Cheers Hillbone in Wagga Wagga Australia.
20250721_081053.jpg
 
hillbone said:
Hi All.
Before I start tearing the bike apart I though I may ask for some preliminary thoughts.
History.A few months ago I replaced my oil pump sealing washer with the correct new one. I also discovered the anti drain valve plunger in the timing cover on my Mk 3 was stuck in the chamber so I replaced it and the spring.
I also noted that the oil pressure relief valve washers were missing so I installed the recommended amount as per manuals.
Upon running the bike with 50 weight oil as always I noticed that when hot, the oil pressure on my trusty Old Britts gauge, had improved from 10 lbs to around 35lbs. Wierdly enough, when firing the bike up the gauge shows 100lbs ( off the scale ) then settles back when warm to 35lbs.
I have now just returned home from 6 weeks away and the garage floor looks like an Exxon Valdez crash.
So, can any one make a guess or an informed reason where this oil has spilled from? Where is the leak?
I havent found it yet and why so much all of a sudden?
Has the 100lbs burst a seal somewhere and where would the exterior leak be?
Any info before a tear down would be appreciated.
Cheers Hillbone in Wagga Wagga Australia.View attachment 120881
Click to expand...
Be thankful it pissed on the floor, no rod bearings or cam were harmed.🏁
 
Maybe the oil tank has fractured at the bottom mount . This bolt and rubber harden up and a fracture of the braze occurs , dumping the oil tank contents .
Mine has been welded up ( no braze left or bolt ) and the tank now sits on a semi solid rubber pad .
Try to find the source , is the tank now empty ?
 
Use a bright flashlight (torch) while laying on the floor to look for wet spots, keep looking up
 
That amount of oil dumped just get some old oil refill the tank and watch where it's coming from, oil tank leak be the first place, also check to see if a oil line hose hasn't come off, if a gasket there be sign where its dripping from but blown gaskets only spue out that much when the motor is running, from sitting then something has failed, the bottom bracket on the oil tank is noted for failing, cracking the oil tank.
As for your oil gauge running 50 grade oil when cold the gauge will run high till the oil starts to warm up it will settle down to normal running pressure, cold oil is thick and even thicker running a straight 50 grade, why a 100psi gauge is recommended.
 
I would suggest you clean up the bike as best as you can, especially the underside (nasty job, but gotta do it) and add a quart of the cheapest oil you can find. Put a disposable turkey roasting pan under the bike. The leak should show up quickly.
 
That much oil looks like a tank or oil line leak.

One thing I never much liked was the glued in oil pipe stubs on some of the oil filters. Not sure if they were original or after market but I lock wired mine so the stubs cannot pull out.
 
The oil tank leak out the bottom mount you would have thought starts with a small leak and then builds. But on mine I had no leak one day and the next day after the bike being parked at work during the day, I got to it at the end of the shift to find the ground covered in oil and the oil level in the tank had dropped 2".

First fix was a new tank as this was back in the 80's, new tanks were cheap. That lasted 10 years before it too got the same leak, so the original had the bottom mount ground off and a plated welded over the top. This is only bolted at the top two mounts and the bottom sits on a rubber pad.
 
If I understand you correctly, you may have too many shims in your OPRV now causing the 100+ psi at start-up. 65 psi should be plenty cold. Check to see if you didn't blow a line off you oil filter block (assuming you have one) as a result of that excessive pressure.
 
Oil pressure doesn’t affect the hoses as the feed is under suction and the return is governed by the scavenge side as well as pushing on an open end (so there’s no pressure).

Still worth checking though.

As the OP had the timing cover and PRV off, I’d be checking for errors there. Oil tank is of cause a prime suspect, but I’m always wary of coincidences, so I would first be looking at what I touched / changed last.

But that’s coz it is usually whatever I touched last that’s f*cked up somehow !!
 
Fast Eddie said:
Oil pressure doesn’t affect the hoses as the feed is under suction and the return is governed by the scavenge side as well as pushing on an open end (so there’s no pressure).

Still worth checking though.

As the OP had the timing cover and PRV off, I’d be checking for errors there. Oil tank is of cause a prime suspect, but I’m always wary of coincidences, so I would first be looking at what I touched / changed last.

But that’s coz it is usually whatever I touched last that’s f*cked up somehow !!
Click to expand...
The reason I mentioned that hose is because the vent on my oil tank got clogged once, which led to my oil tank being over pressurized, resulting in one of those lines popping off. In an off chance excessive oil pressure could lead to excess crankcase pressure then perhaps something similar might occur. Probably a long shot, but only takes a second to check. Pinning a 100 psi gauge is a lot pressure, and no telling where it stopped w/ straight 50wt.
 
An ex-racer in the midlands test a oprv with various shims, the good news if you forget to put any it then it will still provide a decent pressure to the engine, 3 shims is way too much. My modern car uses 3 cylinders and a turbo and the relief is set to 35psi, and I suspect the shell bearings are modern junk with no nasties in them.
 
My MKIII, that happens to have the same paint, cracked the oil tank at the bottom mount, so I agree with others as a good place to look.
 
Updates on oil spill.
Thanks everyone for your comments. I found the leak to be coming from the bottom screw on the primary cover. Bit wierd! So I screwed it out and the case was full of a mixture of petrol and oil.
Unfortunately, before I went away for 6 weeks, I had forgotten to turn the fuel tap off.
So I can only deduce that a float may have gotten stuck open, filling the engine with fuel, which together with some significant wet sumping, leaked past a potential leaky crankcase primary seal, filling the primary case and weeping out that way. The oil tank still had some 2 litres of oil in it, the rest was in the sump and on the ground. The mix of petrol and oil made the spill look much worse.
Does this make sense Shirlocks? I'm guessing.
Cheers and thanks again.
 
Fuel dilution makes sense, it would make the oil less viscous, so it would seap around seals it might not otherwise. I believe I would pull the plugs and squirt some oil down the cylinders and kick it through a few times before trying to start it as the gas probably washed the rings clean.
 
htown16 said:
Fuel dilution makes sense, it would make the oil less viscous, so it would seap around seals it might not otherwise. I believe I would pull the plugs and squirt some oil down the cylinders and kick it through a few times before trying to start it as the gas probably washed the rings clean.
Click to expand...
Will do. Letting air get in now to dry any fuel residue first. Cheees
 
htown16 said:
Fuel dilution makes sense, it would make the oil less viscous, so it would seap around seals it might not otherwise. I believe I would pull the plugs and squirt some oil down the cylinders and kick it through a few times before trying to start it as the gas probably washed the rings clean.
Click to expand...
Definitely pull the plugs and ensure there is nothing left in the cylinders. Otherwise you may get an hydraulic lock which can destroy rods pistons etc.
 

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