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brownjeff, ASE Certified Technician
Category: BMW
Satisfied Customers: 13886
Experience:  ASE Certified Technician, 17 years experience, Dealership Certified, Service Manager for 15 years
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What is the best method to fix a leaking oil drain plug I

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What is the best method to fix a leaking oil drain plug?

I have a 2002 540i with a leaking oil drain plug. The dealer wanted to replace the pan but I requested they try a helicoil. They did with reservations that it might leak. It is my experience that helicoils are used for all types of critical joints so I went ahead.

Well unfortunately they were right, it leaks. I got under the care with a beam torque wrench and found the torque was 100 in-lbs. I tightened it to 150 in-lbs and it still leaked. I tried to tighten it more but the torque would not increase so I assumed that any more would strip the helicoil. Not surprisingly it now appears to be leaking worse.

What are my options?

Thank You

Yes. You have a couple more options. They make a self tapping over size drain plug just for this problem. The plug is bigger than the original and actually makes its own threads as it is installed. They also make a kit which is designed similar to the self tapping plug that once installed it never comes out it has a quick connect fitting on it that attaches to the plug to drain it so it doesn't have to be removed again. These are both after market options and would need to go to a parts store to obtain them.


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Customer: replied 8 years ago.
I am aware of those options. My concern is that there is already a helicoil in place. The hole has been tapped oversize already and the helicoil is made of hardened steel. Likely just as hard as the threads in a self tapping plug. How do I deal with the helicoil insert?

How do I determine what size plug I need now that it has been tapped for the helicoil?


If the helicoil can't be removed I suggest an expandable plug. It is made of rubber with a bolt that goes through the center of it. As you tighten the bolt the plug expands and seals the hole. As far as the size It depends on how big they made it when doing the helicoil. It will either be the size of the original plug or one size bigger.


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Customer: replied 8 years ago.

I was aware of the rubber plug from the forums.

What I was hoping to find is someone who has fixed a leaking helicoil repair. Do you have any personal experience with helicoils? The existing plug is M12 x 1.5, do you know what size the helicoil tap would be?
Yes, I have put may helicoils in. If installed correctly they do not leak. They either made the hole too big and the plug when installed will not tighten up or they did not loc tight the coil to the pan. They could have it in crooked also causing the gasket to not fit properly. If they did loc tight the coil there will be no removing it with out damage to the pan so at this point the best option is going to be an expandable plug.
Customer: replied 8 years ago.
So there is no way to remove the helicoil and start over? Or remove it and try an oversized plug?
The only way to get it out now would be with a chisel as drilling wont work (even this is a difficult task). That is why I suggested an expandable plug as you can leave the coil in and use this plug. It is worth a try to remove it as you don't have anything to loose.
Customer: replied 8 years ago.

Since, if you haven't figured it out by now, I am an engineer. We are not into primative solutions like the rubber plug. Even if it works it's just not right.

It looks like I will have to remove the oil pan and do surgery or replace it. If that's the case I am told that the fasteners on the oil pump have a tendency to come loose. Can I get to them by just removing the lower oil pan or do I have to remove the upper pan as well? This is a 2002 540i auto 4.4 V-8.

This is my last question and I will leave you in piece.

You just need to remove the lower. You probably know the procedure, but if not I will attach some information to help.



Unscrew and remove splash guard.
Drain engine oil.

Unfasten plug connection on oil level switch.

Unfasten lower oil pan section.

Clean sealing surfaces.
Install stud screws (1 and 2) at the locating points in the oil pan.

Note: The stud screws (1 and 2) secure the gasket and oil pan during installation and prevent damage to the sealing lip.

Mount new gasket and lower oil pan section over the stud screws (1 and 2).
Install and tighten down screws. Remove stud screws (1 and 2), insert remaining bolts and tighten.

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Customer: replied 8 years ago.

Thanks. I have the Bentley manual but your sketches are better.

Now all I need to do is get the locktite for the oil pump bolts and thread sealer for the oil pan bolts into the block.

And some patience...


Good Luck,