Out of the four cars I own, there's only really one that can be considered "modern," and next year it'll be old enough to get Bar Mitzvah'd. Still, I have a kid now, and that means I really should have at least one car with some airbags and actual room to haul him and his stuff around. That car is a 2000 VW Passat wagon, the V6 AWD one, and generally I quite like it.
The car, however, has one huge Achilles' heel: the aluminum oil pan. I hate that effing pan. With a capital "E" for "effing."
I know it's technically an aluminum oil pan, but it may as well be made of crépe paper and cheese for all the durability it has. I live in Los Angeles, and LA's vast road network isn't exactly the most pristine, so potholes and other exciting road textures are common. And while all my other cars bounce over them without a care like the lunar rover, the Passat has a very annoying habit of cracking its oil pan on unassuming-seeming bumps.
The current pan on the car is maybe just over a year old. Maybe. I was out with my wife and baby in the car the other weekend, and we hit a bump. Not a huge one, but it made a telltale sound that made our stomachs drop in unison, like some Olympic synchronized stomach-dropping team. When we got home, I peeked under the car and saw the telltale drooling of oil.
So the pan was definately screwed. And, to make things worse, we had to pick up family from the airport the next day. We'd need our car back in service quickly, and the idea of spending a chunk of money (if you go to a mechanic, especially in a rush, this job is $300+) just wasn't appealing. That means, my friends, it's hack time.
Now, I've tried to patch an oil pan on a car before, and it never worked. The oil seepage just keeps any material you're using to patch from taking. For time reasons, I really didn't want to take the pan off, like you really should to do this right. On the Passat, it's not rocket science, but it is a crapload of bolts, a gasket, and you have to unbolt and swing away a big sway bar to get to it. Working under a car on jackstands to do this is a huge, time-consuming pain. So I really wanted to find a patch-the-pan-on-the-car solution.
You may find yourself in a similar situation with a cracked pan and lacking the tools, time, or other resources to remove and replace a pan. If that's the case, read on, pal.
And, spoiler alert, it worked. Thanks to my friend Tom, who provided me with some excellent basic instructions, and my friend Sloan, who was assisting me and didn't talk me out of the inane modification I made to make it work.
The fundamental concept is to use JB weld to temporarily stop the oil leak so the crack can be patched with grey silicone gasket goop material. The oil can't touch anything that you're relying on to make a permanent seal, so that's why the double approach. The JB weld will fail, but ideally the silicone will be set by then.
In practice, this didn't quite work, and I had to add a step involving a dished washer and a penny.
Here's what you'll need: a box of nitrile gloves, sandpaper, brake cleaner, lots of rags or paper towels, JB Weld (quick-setting), Permatex Grey High Strength Silicone, popsicle sticks or similar to mix stuff.
Here's how it's done:
1. Drain the oil. Duh, right? Even after it's all drained, it's still going to seep, but may as well get out as much as you can.
2. Clean, clean, clean. Get your gloves on and use the brake cleaner and paper towels and any other anti-oil cleaning stuff you like to get that oil pan spotless. We want to see the crack we're dealing with. I was lucky and just had one smallish c-shaped crack, but there could be multiples. Evaluate if the pan is worth patching at this point. if the crack/s are small, it's worth a try. Even a small crack can empty your crankcase blood onto the street in an alarmingly short span.
3. Sand! Get that area nice and roughed up so it can take well to the adhesives. Tom called this a "microsurface." It helps.
Once it's clean and roughed, now you have to evaluate seepage. In my case, no matter how long I waited, there was always a constant, irritating seep of oil from the crack. Enough that any substance I tried to patch that crack with would soon be oil soaked and useless. What I needed to do was contain the dripping oil so I could cover it with something that I could then cover with the silicone. That's where step four comes in. Clean again after evaluating the seepage, changing gloves afterwards.
4. Make an oil containment bowl. I used a small extra washer from the alternator pulley of my Beetle. It's shaped like a small, 1 inch or so diameter bowl, with an open bottom. I sealed the bottom with a penny and JB Weld, letting it set then testing that it was solid with a bit of oil. It held. Then, I placed cut small pieces of paper shop towels inside to act as a further oil-slowing device. Then, I JB welded the entire "bowl" over the seeping oil crack. Any little bowl-like washer will work, as long as it has a bondable rim and a little dished area.
The result was the oil dripped into the bowl, soaking the little paper towel bits within, and never escaping the bottom of the bowl. While it filled the little cavity in the bowl, the oil-free rim of the bowl was getting bonded to the oil pan.
4. Over the JB welded seepage-cover, coat with the grey silicone in a nice thin layer. You should have changed gloves before this step, since any oil contamination will ruin everything— remember, that's why we made that absurd tiny bowl. Let the silicone cure as long as you can.
5. Check the progress, add another coat. Hopefully nothing's seeped or dripped. If all's good, apply another thin coat of silicone. New gloves, again/
6. Wait. Hope. Wait. If you can leave it overnight to cure, great. If not, wait as long as you can.
7. Check it out. Is there any oil leaking? If so, you're pretty boned. But, if you were careful and clean every step of the way, you should have a pan that has a weird ugly lump on it, but doesn't drip oil.
8. Oh yeah, fill your engine back up with oil!
I was very pleased this ridiculous procedure worked. I'll have to get an oil pan eventually, but I'd rather wait until I can figure out a protection plate idea or something. Oil pans aren't really fun parts, so may as well make the flimsy piece of crap last.
Good luck! If you're reading this because you're stuck with a leaky oil pan, don't give up!