MadVladCivic

Hi guys,

I broke the bolt that secures the upper radiator mounting bracket to the body.
I had used anti-seize cmpd three yrs ago when I replaced the radiator and was
getting around to replacing the bolt itself when it sheared off. Is there a "fix"
other then drilling out the dead bolt slug?

https://www.hondaautomotiveparts.com...-radiator-hose

Its #20 in the diagram. 1996 Civic coupe. 113K miles.
Thanks.

muellersfan

Picture would help.

TomCat39

Drill it out, then carbide cut the hole large enough for a rivnut. Break the back welded bolt away and then install the m6 x 1.0 rivnut.

MadVladCivic

"Break the back welded bolt"

Hi,
I assume you mean back-welded nut.

How about drilling it out and then tapping that back-welded nut?
I have a bunch of Titanium nitride and cobalt left-handed drill bits.
​​​​​​​Some cutting oil and AeroKroil.

Freedo_Civegra

You can’t just drill it out with a 3/16” drill bit (or 7/32” if you’re really feeling brave) and run a tap in it afterwards to clean up the threads?

Edit: On 6mm bolts, I’ve been able to grind the break flat, center punch, and drill out the broken piece with a 7/32 bit, leaving only threads.

TomCat39

I've never had much luck only drilling out bolts, I've almost always ended up taking out threads in the process. And if you tap it larger, it won't use the OEM bolt. If it's a frame rail bolt hole, I drill it out and after my last one, the rivnut snapped the welded nut off the frame for me but I think it would have been a better install if I either did it prior or ground out the nut portion to make room for the rivnut. I need to get a ball carbide bit to grind past the frame metal after using the straight bit.

I've used a few so far, one for the toque mount frame rail bolts (changed to 1.5 thread pitch since 1.25 M10 is not a standard size so rivnuts and tools are not available. A couple of times for the splash guard/underside bumper cover bolts and once more just a bit ago for the top front bumper cover rubber gasket phillips head bolt.

Freedo_Civegra

Madness, TC. Pure madness.

MadVladCivic

Another option: Overdrill and hammer in a helicoil? The bolt simply holds the upper radiator
retaining bracket. The bracket actually allows play in the radiator. So, even if the new bolt
ends up being an M4, it is still only holding that bracket in place. Not any real constant load.

MadVladCivic

What about a metal-to-metal bonding agent?
https://www.permabond.com/2017/07/21...oxy-adhesives/

Would it hold up to a shear load corresponding to airflow pushing on the radiator surface?

Freedo_Civegra

Drill and tap is the easiest

MadVladCivic

Hi guys!
Update on my broken bolt.
I drilled MOST of the bolt out (M6 x 1.00) using my 5-piece Irwin cobalt left handed drill bits
and a cordless Makita 10.8V drill/driver. Not sure if the bolt was grade 5 or grade 8. No markings to
identify. Used a 7/64 to get the party started. Then plowed w/ a 1/8 bit. Used cutting oil too.
Finished (so far) w/ a 5/32 bit. At no time did the bolt feel/look to back out in the direction of the cut, eg
counterclockwise. There is still a slight shell of threads left in the mating nut. All the bolt above the
nut has been cleared. I can feel some metal shreds when touch the bottom of the receiving nut.
Needs to be cleaned out.

The cut was slightly off-center; however, the nut is welded to a piece of sheet w/ a hole limiting just how
off-center it could be.

In retrospect, I could have drilled away the entire portion of the bolt that was not mated to threads
and then 'started over' w/ the portion that was mated to threads. Two steps.

MadVladCivic

Hi again,

Follow-up on the thread repair options assuming the threads are damaged beyond simple
recovery tapping.

1) Helicoil insert kit, specifically the 10-32 size. McMaster -Carr carries a kit that includes
10 inserts, an appropriate tap (3FPB), the installer tool AND the 13/64 drill bit necessary to
clean the original hole.
# 91732A916 @ 39.36 + shipping

2) Yardley Products offers pressed metal inserts. They will send one free sample.I ordered
632Q8-8ST, which will require a 6-32 size bolt. The original hole will need be gutted w/ a
1/4 drill bit, which may actually go slightly more than the threads of the hole. This is the
cheapest solution as the only cost will be a 6-32 fastener and washer. It should bind very tightly
but a metal-to-metal adhesive could be applied for security.

Those failing, a final option would be to remove the grill and simply add an appropriate M6 nut
from the underside while holding it w/ a wrench while tightening a longer M6 bolt.