Mystery Nut--Anyone Identify?

Whaaaat? I resemble that remark. >:^Þ

It's an exhaust manifold nut. Looks like part of the stud is still in it
too, so that's broken.

Remove the front heat shield for the exhaust manifold and have a look at
all the studs.

 

I also thought it looked like an exhaust manifold nut. The question remains
though, how did it get under the dash? Was Elle under the dash recently and
unknowingly transferred the nut there?

Eric

 

I also thought it looked like an exhaust manifold nut. The question remains
though, how did it get under the dash? Was Elle under the dash recently and
unknowingly transferred the nut there?

Eric

 

i would put money on it being a stud/nut for the exhaust system. either
the a/b/c pipes, the catalyst, or possibly the exhaust manifold. its got
the same patina of a nut/stud thats been in high heat all its life.

 

i would put money on it being a stud/nut for the exhaust system. either
the a/b/c pipes, the catalyst, or possibly the exhaust manifold. its got
the same patina of a nut/stud thats been in high heat all its life.

 

From that photo, looks like one of those Castle nuts or Self-locking
nuts from the front suspension. There are 4 identical sized nuts (all
12x1.25 mm) but with different torque settings (page 18-8 of service
manual; 1991 Civic). One on top of the strut housing, and two at the
bottom, and another one at the end of the control arm. If you need the
diagram, do drop a line, and I will scan the page and send it over.
Hope this helps......

 

From that photo, looks like one of those Castle nuts or Self-locking
nuts from the front suspension. There are 4 identical sized nuts (all
12x1.25 mm) but with different torque settings (page 18-8 of service
manual; 1991 Civic). One on top of the strut housing, and two at the
bottom, and another one at the end of the control arm. If you need the
diagram, do drop a line, and I will scan the page and send it over.
Hope this helps......

 

No; miscommunication. My Civic was on ramps, and I was under
the car, grinding out one of the control arm bolts, for a
long time (see other thread). About mid-day I moved the
cardboard and wood planks on which I lie for this sort of
work and found this lock-nut (with, as Tegger said, part of
a stud attached). I figured the grinding vibrations knocked
it free.

I'll get a closer look tomorrow. Car's driving okay, all
things considered (especially all my monkeying with
everything).

Thanks, folks, this will save me a lot of time.

 

No; miscommunication. My Civic was on ramps, and I was under
the car, grinding out one of the control arm bolts, for a
long time (see other thread). About mid-day I moved the
cardboard and wood planks on which I lie for this sort of
work and found this lock-nut (with, as Tegger said, part of
a stud attached). I figured the grinding vibrations knocked
it free.

I'll get a closer look tomorrow. Car's driving okay, all
things considered (especially all my monkeying with
everything).

Thanks, folks, this will save me a lot of time.

 

Is that 12 mm the nominal diamter of the suspension bolts
onto which these suspension self-locking nuts fit, though?
That sounds more likely.

The 12 mm I mention for this mystery nut is the nut head
measurement. That is, a 12 mm socket fits it. The nominal
diameter of its corresponding stud appears to be 6 mm or 8
mm. (The stud diameter is a little hard to measure while
it's stuck in the nut.)

Thanks for the input. I'll update tomorrow, hopefully.

 

Is that 12 mm the nominal diamter of the suspension bolts
onto which these suspension self-locking nuts fit, though?
That sounds more likely.

The 12 mm I mention for this mystery nut is the nut head
measurement. That is, a 12 mm socket fits it. The nominal
diameter of its corresponding stud appears to be 6 mm or 8
mm. (The stud diameter is a little hard to measure while
it's stuck in the nut.)

Thanks for the input. I'll update tomorrow, hopefully.

 

Most 12 mm nuts on a Honda are threaded for an 8 x 1.25 mm bolt.

Eric

 

Most 12 mm nuts on a Honda are threaded for an 8 x 1.25 mm bolt.

Eric

 

Hello: I just checked the stud/nut diameters with a caliper after your
and Elle's posts. Yes, you two are correct: the 12x1.25 mm that Honda
manual refers to is the stud diameter and not the nut diameter (should
have remembered this...my apologies). For the 12 mm diameter nut Elle
refers to, looks like the corresponding stud size is 8 mmx1.25 mm as
Eric correctly suggests. If yours came from the front suspension, there
is just one such self-locking-nut according to the front suspension
diagram; 8x1.25 mm, stabilizer bar /lower arm attachment. According to
the diagram, in the front suspension, there are
6 of 12x1.25 mm self-locking/castle nuts (missed two of these in my
earlier post!)
5 of 10x1.25 mm
1 of 8x1.25 mm; all self-locking or castle nuts. As Eric and you
indicate correctly, the 12, 10 or 8 referred to in the diagram are for
the stud diameter.

 

Hello: I just checked the stud/nut diameters with a caliper after your
and Elle's posts. Yes, you two are correct: the 12x1.25 mm that Honda
manual refers to is the stud diameter and not the nut diameter (should
have remembered this...my apologies). For the 12 mm diameter nut Elle
refers to, looks like the corresponding stud size is 8 mmx1.25 mm as
Eric correctly suggests. If yours came from the front suspension, there
is just one such self-locking-nut according to the front suspension
diagram; 8x1.25 mm, stabilizer bar /lower arm attachment. According to
the diagram, in the front suspension, there are
6 of 12x1.25 mm self-locking/castle nuts (missed two of these in my
earlier post!)
5 of 10x1.25 mm
1 of 8x1.25 mm; all self-locking or castle nuts. As Eric and you
indicate correctly, the 12, 10 or 8 referred to in the diagram are for
the stud diameter.

 

That's what it looks like to me - a high-temperature locking nut.

Mike

 

That's what it looks like to me - a high-temperature locking nut.

Mike

 

I took the exhaust manifold shroud off today. It is indeed
an exhaust manifold nut (with broken-off stud stuck in it).
It's the one nearest the distributor.

I am amazed at how many people (Nasty, Tegger, Eric,
SoCalMike) nailed this, and with a fuzzy photo, too. What a
phenomenal newsgroup!

I see the stud on sale at Majestic online for a couple
bucks.

I reckon I'll see how my ball joint castle nut/stud work
goes today and then make a trip to the junkyard. I think the
front desk man and I could become an item...

Much obliged for everyone's input. This all is valued work
to me, and I couldn't do it nearly as efficiently (and at
some points, not at all) without the extensive experience of
so many of you.

 

I took the exhaust manifold shroud off today. It is indeed
an exhaust manifold nut (with broken-off stud stuck in it).
It's the one nearest the distributor.

I am amazed at how many people (Nasty, Tegger, Eric,
SoCalMike) nailed this, and with a fuzzy photo, too. What a
phenomenal newsgroup!

I see the stud on sale at Majestic online for a couple
bucks.

I reckon I'll see how my ball joint castle nut/stud work
goes today and then make a trip to the junkyard. I think the
front desk man and I could become an item...

Much obliged for everyone's input. This all is valued work
to me, and I couldn't do it nearly as efficiently (and at
some points, not at all) without the extensive experience of
so many of you.

 

Broken studs are very common. I had one too. Mine broke below the surface
of the head. My mechanic removed it, but wouldn't tell me how (trade
secret, or so he says...). It was done at the same time as my head gasket
replacement, so the machine shop that trued the head probably did it.

The problem is that exhaust pulses are quite violent. This is the reason
you need heat-resistant "prevailing torque" nuts. The nuts don't vibrate
off, but the pulses often break a stud.

Funny, the one that broke on mine was the one nearest the timing belt. It
must be a random thing.