Oil pan Plug thread size

[85Hokie]

I have run across an unusual problem and need to help a friend with.

Long story somewhat short - buddy of mine has a 2006 Jeep TJ - I recommended he buy one of these quick oil plugs that I have used for years,

I have them on all my cars/trucks/Jeeps - work perfectly I might add.

they are the
Fumoto Oil Drain Valve

In my opinion they are worth every penny much like a lock-n-lube for grease guns.

Anyway - he buys one, yesterday he gets under the Jeep (4.0 inline 6) and has the 5/8" wrench in his hand - comes out from under, "nope that is way too big!"

I said that is what it is supposed to be - 5/8!

So after trying other sizes I had him a pair of vise grips - yeah I know, not the best tool - but everything I had was not the right size!!!

ANYWAY - took the plug off and stuck the new .500 Fumoto plug in - goes in and does not even touch the threads! Big wtf moment!

SO quickly I come to the conclusion that the PO must have buggered up the old plug and placed a "new" plug in it.

I took the plug out and measured it with a dial indicator - a good indicator. The hex head was about the same size as the bolt which I thought was a bit strange, most bolts have a larger head than the major diameter.

First thing I noticed - it is a straight bolt, no front end self "new" thread starter.

I measured the major diameter and the minor - here are those numbers .536" Major -carefully measuring the OD of the thread and then measuring the minor diameter of the threads I got .492"

So I google the crap out of those numbers and find nuttin! Hell I even took the damn thing to a hardware store that has the little what is this thread pitch gauge tool - nothing close.

I even tried metric and converting that to SAE I still find nothing close.

SO - someone that has been down this road a couple of laps - WHAT HELL IS THIS bolt and why is it such an uncommon thread?

 

[John T]

Thats the first Fumoto valve I've seen with the litlle plastic protector....

That must be something new... ?

I don't remember the originals having the plastic clip.


I never liked those for that reason.... on any vehicle. If that dump lever gets caught on a stick or anything.... And decides to open up.... Kiss your bearings goodbye.

I'm still not sold on them.... Even with the lever protector... But it IS a clever idea.

as far as the thread size you need, I would put a pitch gauge on the old plug or the threaded hole.

It might be metric.

 

[John T]

FWIW...

My 1998 Jeep XJ oil drain plug is 1/2"-20 (takes a 5/8" wrench)

4.0 engine. factory stock

 

[GeoHorn]

We have discussion-threads (had to add that word “discussion” to this “thread” thread…. …) …
in which oil-return tubes, drive-shaft tubes, tie-rod joints, etc etc are bent/trashed/leaking…. because the tractor was used in brush or rough terrain.

I would NEVER trust a “quick drain” on any vehicle which did not thoroughly protect that drain plug/device…

 

[85Hokie]

We have discussion-threads (had to add that word “discussion” to this “thread” thread…. …) …
in which oil-return tubes, drive-shaft tubes, tie-rod joints, etc etc are bent/trashed/leaking…. because the tractor was used in brush or rough terrain.

I would NEVER trust a “quick drain” on any vehicle which did not thoroughly protect that drain plug/device…

While I agree with the potential problem of hitting something and having it spring open is a possibility - I would not have installed them on my cars.

At my current age of lack of mobility and patience - the idea of climbing under KNOWING I do not need a wrench to drain the oil FAR outweighs the 1 in a million of hitting something and breaking it off.

My question was - what is the size of the bolt - NOT the merits of the use of the drain.

 

[GeoHorn]

…

My question was - what is the size of the bolt - NOT the merits of the use of the drain.

I wasn’t attempting to answer your question…. I was discussing the merits / de-merits of quick-drains.

 

[Dustball]

BSPP pipe plug?

 

[GreensvilleJay]

maybe 14mm ?
just how accurate is your 'good' dial indicator ?
any markings on the mystery bolt ?

easy test, run taps into the hole to see which one 'feels' right

 

[85Hokie]

maybe 14mm ?
just how accurate is your 'good' dial indicator ?
any markings on the mystery bolt ?

easy test, run taps into the hole to see which one 'feels' right

AS for the tap - I could have done that - and I have a entire tap set, but taking to the local TSC and using there thread measuring device - you know the one you stick the bolt ON or IN and spins?

As for the BSPP - those are tapered, this was a straight tread.

AS for the dial indicator, it is good - +/- .001 , now if I was using a veneer caliper - I am sure I was off!

 

[Dustball]

As for the BSPP - those are tapered, this was a straight tread.

AS for the dial indicator, it is good - +/- .001 , now if I was using a veneer caliper - I am sure I was off!

BSPP is parallel. BSPT is tapered.

 

[North Idaho Wolfman]

Picture of the plug and plug head might help?

 

[85Hokie]

Picture of the plug and plug head might help?

Brother,

had I been smart I would have taken a picture when I was measuring it!!!!

But it looked a lot like post #7 - but it was straight threads, no taper, no cutting teeth.

A hair over 1/2 - 20

 

[GrizBota]

Thread pitch? Count how many threads per inch. Or per whatever length you care to (longer is better, reduces the error) and convert it to threads per inch as well as millimeters per tread. If you have a scosh over a 1/2” it might be 14 mm. The major dimension you provided converts to 13.6 mm (initially I posted stating 14.30 mm, incorrect).

As to the hex size, if it’s pretty close to the plug thread diameter it might be a 14 mm (very close to a 9/16”, sometimes interchangeable) or a 15 mm, which is an oddball and many metric socket and wrench sets leave it out.

Not that it matters to your inquiry, but the plug in that Jeep will probably result in less trouble than the quick drain valve in the long run.

 

[GrizBota]

maybe 14mm ?
just how accurate is your 'good' dial indicator ?
any markings on the mystery bolt ?

easy test, run taps into the hole to see which one 'feels' right

Better test, run the plug into the non flared side of your dies or into known nuts. No need have a tap bugger the thread in the pan. YMMV.

 

[85Hokie]

Better test, run the plug into the non flared side of your dies or into known nuts. No need have a tap bugger the thread in the pan. YMMV.

Not 14 - tried that ....... it measured OUT to 13.6 mm and I KNOW that aint real at all!

 

[Runs With Scissors]

While I agree with the potential problem of hitting something and having it spring open is a possibility - I would not have installed them on my cars.

At my current age of lack of mobility and patience - the idea of climbing under KNOWING I do not need a wrench to drain the oil FAR outweighs the 1 in a million of hitting something and breaking it off.

My question was - what is the size of the bolt - NOT the merits of the use of the drain.

I think my chances of knocking that thing off are closer to 1 in 3.

I was a Jeep mechanic back in the day, but I never measured the threads on the oil pans. If I needed one, I just headed up to the "parts counter".

 

[GrizBota]

Not 14 - tried that ....... it measured OUT to 13.6 mm and I KNOW that aint real at all!

Indeed 0.536” is 13.6 mm, not 14.3 mm (which I incorrectly stated initially). You are correct. Seems like you’ve got a real oddball plug tread.

 

[GreensvilleJay]

curious, google .536 bolts... this popped up

https://www.napaonline.com/en/p/NOE6411578

so 1/2" fine thread bolt ?

makes sense, fine threaded.

 

[Dustball]

Aside from the 1/4" BSPP I suggested, it may be ISO 6149 Metric Straight Thread M14x1.5. What was the drive size measured at?

Thread Identification - Checkfluid

www.checkfluid.com

 

[North Idaho Wolfman]

curious, google .536 bolts... this popped up

https://www.napaonline.com/en/p/NOE6411578

so 1/2" fine thread bolt ?

makes sense, fine threaded.

.536 KNURL not thread