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Discussion Starter · #1 ·
I had some oil dripping from the sump tank. My first thought is I over torqued the drain plug on it. I lifted the car and saw the streaks from about half way up the tank. So I got some needle nose pliers and removed the sticker to reveal a hole behind the sticker. I talked to McMedics and he said he’s seen it before, he said it’s welds on internal baffles that fail over time and crack the tank. He also said it’s an engine out job to replace the tank. So I’m going to try fixing it in 3 steps.
1.) Get JB Weld Aluminum TankWeld and try to patch it with the fuel tank in. Only about 1 or 2” of clearance max.

2.)If 1 does work, I’ll have to drop the fuel tank and get access to that face of the oil tank to patch it.

3.) If 2 doesn’t work then I’ll have to pull the motor and replace the tank. (I really don’t want to do option 3 😩)
 

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You can try and patch it, as long as you prep the area well, but with the space you have that aint guna be easy. FYI, you can get that tank out without taking the engine out. Its been done before.
 

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Discussion Starter · #3 ·
You can try and patch it, as long as you prep the area well, but with the space you have that aint guna be easy. FYI, you can get that tank out without taking the engine out. Its been done before.
Do you have a link to a write up or video on how that’s been done? Would love to do some research on it while I’m waiting for this TankWeld to dry.
 

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[QUOTE="bbroetsky, post: 1811740, member: 19977"
2.)If 1 does work, I’ll have to drop the fuel tank and get access to that face of the oil tank to patch it.
[/QUOTE]


Once you get to this point, you will have sufficient access to remove & replace it. Engine removal not needed.
 

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Discussion Starter · #6 ·
It's not an engine out job. This only happens on early 12C's. The new tank is updated and this won't happen again. I highly recommend biting the bullet and just replacing the oil tank.
Hey Dan,

Any idea what year the tanks were updated? I called Mac of Scottsdale and my wholesale price for a tank is $2500. Luckily I’m local to AZ Cycle Parts and they have a few used ones from 650’s.
 

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Hey Dan,

Any idea what year the tanks were updated? I called Mac of Scottsdale and my wholesale price for a tank is $2500. Luckily I’m local to AZ Cycle Parts and they have a few used ones from 650’s.
I believe they were updated in 2013. The easy way to tell is the updated tanks have a cast piece where the drain plug is. The old ones do not have a cast piece. Every 650S will have an updated tank.
 

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Discussion Starter · #8 ·
After doing some research and going down to my local McLaren salvage yard (AZ Cycle parts) I’ve come to a conclusion. The original tank part number is 11F1028CP.02 found on MP4’s. The updated part number is 11F1178CP.03 which the only visual differences are the bottom section is cast so when you torque the drain plug you don’t crack a weld and the back side (the side with part # sticker in the photos) where mine is cracked, is reenforced with exterior welds. The updated tank is found on all 3.8L Mclarens regardless of coupe or spider. The dealer wants around $3000 retail for the tank. I picked up mine from AZ Cycle Parts off a 2019 570s for $400 and it looks brand new. I hope this info will help MP4 owners in the future when this happens to their tank.
 

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After doing some research and going down to my local McLaren salvage yard (AZ Cycle parts) I’ve come to a conclusion. The original tank part number is 11F1028CP.02 found on MP4’s. The updated part number is 11F1178CP.03 which the only visual differences are the bottom section is cast so when you torque the drain plug you don’t crack a weld and the back side (the side with part # sticker in the photos) where mine is cracked, is reenforced with exterior welds. The updated tank is found on all 3.8L Mclarens regardless of coupe or spider. The dealer wants around $3000 retail for the tank. I picked up mine from AZ Cycle Parts off a 2019 570s for $400 and it looks brand new. I hope this info will help MP4 owners in the future when this happens to their tank.
az cycle has a ton of great parts
 

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known problem with internal baffle vibrating and not enough welded area .not related to external forces applied to tank.
Yep. Another thing to add to the list of desirable repairs / updates when looking at early cars.

McLaren still do this as an engine-out job - mine was recently replaced under ESC.
 

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Discussion Starter · #15 ·
Yep. Another thing to add to the list of desirable repairs / updates when looking at early cars.

McLaren still do this as an engine-out job - mine was recently replaced under ESC.

And they pulled your engine to do it?
 

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Engine out is the first step for the dealer for a bunch of jobs I've done on the Phaeton without removing the engine. Oil cooler pipe was the worst one, I had to lift the engine a couple of inches for that one. I have no idea why dealers love removing engines, other than they get to charge more for the job.
 

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I guess it is luck of the draw, this isnt all that common. Mine is fine still. Early 12c. They are all hand made tanks so some will be weaker than others.
 

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I guess it is luck of the draw, this isnt all that common. Mine is fine still. Early 12c. They are all hand made tanks so some will be weaker than others.
I suspect that it also depends on the mileage and the number of higher g-force turns. Given the cost, I'd be looking for it to have been changed when buying, if I hadn't already.
 
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