Hey guys,
I recently got a reman motor put in and its been running great. Did a oil change a few hundred miles later, and me being an IDIOT and not thinking correctly over tightened the dang bolt and i can see the threads on the aluminum drain plug got squished... GREAT...
So, Ive been driving around the past few months with a tiny leak. (drips a couple drops a night).
Anyway, i finally decided to just replace the plug during my next oil change. i got a 1/2-20 threaded drain plug. it looks different than the one currently on there, but matched my previous motors drain plug... i drained the oil ad when i inserted the new plug it just went in... the threads aren't. even touching! So I have no clue what the threads are for this oil pan. and i cant take the plug that came with it anywhere cause its now back in my jeep and leaking still lol. (jeep is my daily driver) anyone know of a larger threaded oil drain plug that came on these motors? or any solutions? thanks. (yes im dumb for stripping the nut on my brand new motor lol)

 

My guess is they used a HeliCoil insert and a bigger bolt.


Or bought an oversize oil drain plug.

https://www.napaonline.com/en/p/NDP7041362

Now these are just random sizes I linked to show you what I am talking about.

 

Why did they put an aluminum pan on it? Are you talking a 4.7 or 3.7? Either one doesn't belong in the XJ section. Always specify your model and year when asking about it. Remember, garbage in, garbage out. We need the right data.

 

Sorry I guess you can’t see the specs of my car on mobile. it’s on a 4.0. You misunderstood what I said or maybe I worded it wrong. The pan is steel. The bolt is aluminum. The bolt is the one stripped

 

My bad! I saw that but never heard of a 4.0 with an aluminum pan, however even that's not the case. Obviously it's not a 1/2-20 thread either because an aluminum plug that size would strip out in a heartbeat, which also means it's an aftermarket pan. You're going to have to do some noggin' pokin' and figure out if it's a fine thread or course thread and try some different size bolts in it to see what fits. Luckily, the weldnut in the pan is case hardened to prevent being easily stripped and the plugs are soft for the same reason. It should be an Imperial (inch or SAE) thread, but with aftermarket anything goes. Here's a wild one! See if a spark plug screws in. Early military specs for jeep 2.5L 4-bangers was 14X1.25mm for spark plugs so they could be used as an emergency plug in the field. That one is sort of out-of-the-box so to speak. Valvoline Instant Oil Change used to have them, but I doubt they still do. You may have to find one online, if that's what it is. If you have to use a spark plug for a while, DON'T break it off because it will leak. The reason I suspect this is the one is a 1/2-20 plug will just slide into that hole. The OE 14X1.25mm plug is steel, BTW. Just had a thought! An 02 sensor plug is the same thread.

Now that I've toasted my brain thinking of possibilities, I hope it helps.

 

@ dave1123
Are you saying factory is not a 1/2-20?

 

No, OE is 1/2-20, but some early models were 14X1.25 mm for the military. I'm just saying his pan may not be your normal everyday pan. The best case scenario is the 1/2-20 with the big inch-and-a-quarter rubber washerhead Mopar plug. Those you just tighten until they stop, then no more. Steel pans are generally fine thread and aluminum pans are course thread. Honda cast aluminum pans actually have a torque spec of 28-32 ft/lbs so you don't damage the threads. In the 70's they used a dead soft aluminum gasket that had to be replaced every time. IDK about today.

 

Yeah I was all confused.

 

Just as an aside, I just sent my 00 4.0L clean-side shortblock to the shredder because nobody around here wanted it, not even engine shops. Damn shame because all it needed was pistons and bearings after 252K miles. The bores were still within specs to use standard rings! High side wear limit though.

 

Cool I’ll see if that size fits. The 1/2-20 with the red big washer was the one that didn’t fit. Just slid in. Thanks for the help.

 

Here’s the update y’all. Took the bolt with me to Ace hardware and found out it’s a 9/16 x18... interesting.... so I bought a short grade8 bolt, came home to put it in and it doesnt thread in very easily. It threaded in pretty well the first 3 or 4 rotations and then got kinda hard. So I ordered a 9/16x18 thread tap. Guess we will see what happens when it gets here.

 

Did you or did you not try a spark plug? Reason I ask is because 14X1.25mm is pretty damn close to 9/16-18. 9/16 is not a commonly used thread for anything, just like 1/4-24 or 7/16-16. The last time I saw a 1/4-24 thread was on a carburetor idle needle. I had to make one for an ancient outboard motor.

If it IS a 9/16-18, you're going to want a grade 3 or 5. You want something softer than the pan. Also how about seal gaskets? Where are you going to find them? I guess a spark plug gasket would work as long as the bolt head will cover it.

 

The 14x 1.25 was too small as well. It’s more like a 14x1.5. Like the oversized drain plug. I may try it. Also anyone ever have luck with those rubber expandable plugs. They go in and then you tighten the bolt and the rubber expands in the drain hole?

 

If you're talking about the ones with the toggle bolt, yeah, they work okay, but don't last long. The rubber deteriorates quickly and it's hard to get the toggle bolt out. Plus they are very messy to drain. I don't have any experience with the ones with the expansion bolt. I'm wondering about a full threaded Helicoil insert like you would use for repairing stripped out spark plugs. Those screw in and then you use a flaring punch to lock it in place. Those would probably bring the threaded hole down to 1/2" although the flaring punch might break the welded insert loose. IDK man. I've just about blown my wad trying to figure this out.

 

I appreciate the help. So everything I’ve tried so far today hasn’t worked. I have a thread tapper coming in. For now I just put some non-hardening RTV on the furthest thread (closest to the bolt head) and so far so good until the thread tapper comes in