Pinhole in steel oilpan: weld or epoxy or...?

Finally have a chance to get to the bottom of the small but annoying oil leak in my 128i. BMW, in its infinite wisdom, put a steel pan on the manual cars (perhaps as some sort of subtle punishment for continuing to resist the will of our Bavarian overlords and their vaunted technological wizardry), and I have just discovered that mine has a tiny pinhole amid the rust. I've cleaned up the rust and will treat those areas with a rust converter. My question is how best to seal up the hole. It's near the mounting for the oil quality sensor, but not on the sealing surface, so it doesn't have to be perfectly flat. My first instinct is to weld (I have a small MIG), but not having dealt with this before I figured I'd consult the hive for (better?) alternatives. Any thoughts?

Do you have an idea as to how thin the rusted area has become?

I had this happen last winter on my Saabaru, although on a more severe scale (1-2sq inch area was thin enough that oil was seeping through) and I got some JB Weld that was safe for oil and gas and used that. It's been over a year and it's not leaking again, so that should work for a pinhole.

On the other hand, if you have a welder, I feel like that could give a cleaner looking repair. 

You will eventually give up and replace the oil pan.  Save yourself the aggravation and do it now.

Epoxy won't stick. Mig will blow through the rust, ignite the vapors and blow the valve cover off.  A wood screw in the hole won't hold.  A diaper will only hold so much oil.

How difficult is the pan to remove, and how expensive is it to replace?

I would first epoxy (JB Weld) a metal "patch" to the area...see how that holds; make sure it's super clean and somewhat roughed up so a good bond occurs.   If that fails, just replace it. 

The pan is $900 and an enormous PITA to replace; I recognize it might have to happen at some point, but I need a right-now solution for the moment. I'm going to poke and probe the area around it to see how thin the metal is - it didn't seem too bad when I wire-brushed the rust off, but obviously I don't want to blow through it with the welder. If I do decide to weld, I'll pull the oil filler cap to avoid blowing the valve cover off.

Any thoughts on welding or epoxying a small (quarter-sized?) metal patch over the hole, rather than just attempting to fill the hole itself?

Uff, looks like you are looking at $700+ for a new pan.

I would remove and try to have it welded probably.

Looks like someone switched to the aluminum one:

https://www.1addicts.com/forums/showthread.php?t=1633304

In reply to 02Pilot :

Can you get it clean enough to weld on the car?

NOHOME said:

This is what I would do. 

Many many years ago I towed my race car with an early 90s ford E350 creeper van with a 7.3 non turbo diesel.  Thing had an E4OD trans that idled along the freeway.  Heading out to road america I loaded everything up and decided to change the oil - its a long tow.  Noticed the oil pan was damp and wiped up the pan only to reveal pinhole leaks along the front edge of the pan.  Freaked out cause now I thought I was screwed.  Drained the oil, brake cleaned the pan, wire brushed, more brake clean - and then a full coating of JB weld (while pan was empty from oil change).  If it could just get me there and back I could put a new pan on.   No leaks and 5 years later I sold it with the JB weld pan.

If it's a pinhole on the outside, it's 10x worse on the inside. Oil floats on water, remember?

Replace the pan.

In reply to 02Pilot :

I would go with the weld/epoxy a small patch on like you said. I'd just make sure to drain the oil, and spend lots of time cleaning/expanding access to the area so you can do a good job. If you're welding on flux core, I'd go with the jb weld.

The rust is definitely on the outside; I can reach in and feel the smooth surface on the inside opposite the rusty spots. I have good access and should be able to get it thoroughly clean. The metal feels pretty solid when probed.

I've got a gas setup for the MIG. I've got JB Weld. I don't have one of the self-tapping screws with a seal that was shown above - I'm not sure how I would feel about enlarging the hole with something like that.

FWIW, when I had my car at the dealer for a recall recently, they noted the oil leak and assumed it was from the pan gasket. As a courtesy, they quoted me the repair (gasket only, not pan replacement): $2200. Even my indy told me "I don't even want to do that job. I'd stick a piece of cardboard under it."

I'm working on finishing up the oil filter housing gasket now. Then I'll go back underneath and figure out how I'm going to proceed.

$700 + for a steel oil pan!? That's almost dry sump money around here!

02Pilot said:

Any thoughts on welding or epoxying a small (quarter-sized?) metal patch over the hole, rather than just attempting to fill the hole itself?

If you do try epoxy you will need to make it very clean. Then fill the hole. Next, cover the whole rusted area with epoxy. Place a metal patch over that area.

Pop rivet with a little RTV on it. 

Permatex makes a spray on leak stop product that apparently works well for oil pan leaks. I have a can in my shop waiting for me to get around to trying it.

https://www.summitracing.com/parts/ptx-82099?seid=srese1&gclid=Cj0KCQjwla-hBhD7ARIsAM9tQKuViZun2Yun_A1txTpmAFG0KICUoZuObXYWa08TmXLiRSU0IUrCgxYaAmasEALw_wcB

I had a 1987 MR2 with that had a 1/2" crack in the oil pan right next to the drain plug. I drained the oil, cleaned the pan with Brakleen, and slathered some JB Weld on it. Never leaked again after that. 

I say try JB weld. Worst case, it doesn't work and you have to remove the pan, sand/grind it off and have someone weld it. 

I would clean it up with a wire brush and brake clean, then use of of these kits: 

Permatex 09101 Fuel Tank Repair Kit

Clean it thoroughly and use JB Weld. I've done that to repair cracked transaxle, motorcycle gas tanks and well as an oil pan........hell it fixed the cracked exhaust manifold on my van.

My Tacoma's rear end has many pinholes in it. I cleaned it with alcohol and JB Welded it. Held up all winter no problems.

So, the update. I decided to try welding it up first. Bad idea - either because the metal was worse than I thought, or my crappy welding skills, it just opened up the hole; it's still small, but it's bigger than it was. I stopped quickly, but obviously needed a new plan. Got a piece of thin steel and cut an L-shaped patch to skirt one of the studs to which the OQS attaches and shaped it to match to contour of the pan, avoiding the OQS seal area. Ground down the small blob of weld and hit everything with a liberal soak of brake cleaner, including getting the little red tube up into the pan and directing it at the back side of the hole. Slathered on some JB Qwik and pressed the patch into place. I then put in the OQS, which overhangs the patch and might provide a little bit of clamping force. It's sitting there curing now (4-6 hours, supposedly). I'll wait until tomorrow morning to refill the oil and see what happens; I left the belly pan off so I could easily observe the area to check for leaks. It's going to require a few local test runs before I trust it to survive heat cycling. I've also got some brush-on Rustoleum rusty metal primer and satin black to cover up the other areas that showed rust.

What kills me is that the automatic trans cars got an aluminum pan, which is also much cheaper brand new than the steel, M/T only one.