Help needed! Identify this bolt found loose in oil pan?

R

Red91Laredo

NAXJA Forum User
Location
Portland, Oregon
So I was changing my oil the other day and noticed that the oil was draining out really slow. I thought that was strange but it was pretty cold out and I had recently added 1/2 bottle of Lucas oil stabilizer to the engine so I didn't think much of it. Well, when I went to put the drain plug back in, I saw the threads of a bolt sticking out the oil drain hole. So I dropped the pan and this is what I found (see pics below). It's a small bolt about 22mm in total length and threads about 7.7mm in diameter. It doesn't look to have been broken off and isn't damaged in any way.

After removing the oil pan and shining my work light in every nook and cranny I can't find anything on the bottom end of the engine that is missing a bolt. Before I got the pan off I had a theory that it might be an oil pump bolt, but both of those bolts are still there. I don't know how large the oil galleys in a 4.0L are, but is it possible it came from elsewhere in the engine (valvetrain? timing set?) and made it down into the oil sump?

I don't know how long this bolt has been in my oil pan but I assume this happened within the last 3000 miles. I've done all the oil changes on the Jeep since I got it (I've put 25k on it so that's 7 or 8 oil changes) and I think I would have discovered it by now. Since the oil draining out was enough pressure to sweep it into the drain hole I assume that would have happened previously. There's no sludge in my oil pan (at least that's good news) so it's not like it was stuck in place down there.

The engine is running fine. I just came back from a 2500 mile road trip and it ran great. I'm afraid to fill it back up with oil and drive it until I find out where this bolt goes and replace it, obviously...

bolt2.jpg


bolt1.jpg


bolt1.jpg.html
bolt2.jpg.html
 
Last edited:
Looks like an oil pan bolt got dropped during assy. The only bolt roughly that size would be an oil pump bolt, but that looks too short.
 
I say it may have been in there since day one. Look at the bottom of the pan and see if it is polished.
 
I agree, that looks like one of the rear "corner" pan bolts. 4 of the pan bolts are 5/16 x 18. One at the front is has a stud head on it and the other three are just regular 5/16" bolts and are short like the one shown.

It was dropped in at the factory by accident, no big deal and no damage done.
 
I didn't find any missing bolts to the oil pan, however the bolt does fit the two larger holes at the front corners of the pan & two immediately next to the rear main. The existing bolts that were in those locations do look very similar in size to the bolt I found in the oil pan (other than the one which is a stud), they are slightly different in that they have a washer attatched to the bolts. I'll post a pic in a moment. I noticed the oil pan was sealed using a rubber gasket and had silicone in the corners- could that be a factory job or is it an indicator that the pan has been removed before?
 
old_man said:
I say it may have been in there since day one. Look at the bottom of the pan and see if it is polished.
Click to expand...

Truth.... Many years ago, I was replacing an 200 ci engine in '65 Ranchero. When I removed the oil pan and began scraping the sludge at the bottom, I found a relatively new 1/2" Snap On wrench at the bottom of the pan. The sludge kept it in place after all the years....

Must have been there from the factory as we were the original owners....
 
Is this something that is relatively common? You guys seem pretty convinced it was just dropped in the pan and I hope you're right but I'm sure you can understand I was pretty startled to find it there...

Here's the bolt from inside the oil pan on the left and one of the corner bolts on the right. Not identical, but looks close enough to assume that it could be a pan bolt? The ones off the outside of the pan have a washer attatched and the one from inside it has it sort of built into the bolt head.

2012-11-26_16-13-29_623.jpg


2012-11-26_16-12-14_993.jpg
 
Last edited:
Moved to OEM tech...

There are four screws on the oil sump that are 5/16"-18x3/4", and that looks like one of them. The four larger screws are located at either end of the "long run" rails - were all four in place?

That may have been dropped in during a job where the oil sump was removed, and then just replaced. A screw loose in the oil sump won't get picked up by the pump, it's too large to fit through the mesh on the pickup. It would really only be a problem if the engine were inverted (while running) and still going for a couple of seconds or so - so that's not worrisome.

The only other thing I can think of would be one of the oil pump mounting screws, but I think the short one is 5/16"-18x1". Were there two screws retaining the oil pump when you looked at it? Both of those are threaded 5/16"-18, the shorter one is 1" or so, and I think the longer one is 2-1/2". I can't think of anything else that would have 5/16"-18 screws down there (and if that takes a 1/2" wrench, it should be a 5/16" screw.)
 
jeeperjohn said:
Maybe it is from the front of the block near the timing gear. Maybe one of the cam plate bolts? :dunno:
Click to expand...

That's one thought I had... I've never had the timing cover or valve cover off a 4.0L before so I don't know if there are bolts like this found under them. There definately seems to be enough room for a bolt this size to find it's way from the timing cover to the oil pan. Although it seems unlikely that it'd make it there completely unscathed. Any thoughts on that?

I'm in the process of putting the pan back on, so I just hope you guys are right with the misplaced oil pan bolt theory.
 
You must log in or register to reply here.

Similar threads

T
Identify bolt holes on driver side engine
Replies
3
Views
120
q2quest
q2quest
A
93 xj OBD 1 Code 11 Crank no start
Replies
1
Views
19
Akton
A
W
May regret using Rotella in my '96 XJ
Replies
11
Views
1K
75SV1
7
R
Random Hard Start, Low Power
Replies
0
Views
108
rtd16
R
T
Oil Pump insert in block missing
Replies
2
Views
105
tparkerxj
T
Back
Top