gta90

iTrader: (1)

Can anyone help with a broke/stuck SUPER-strength steel bolt (14mm hex head, 3/8" x 1-1/2 I'm told) in the intake manifold (thermostat housing bolt -- the non-stud one)? First time I ever worked with a stuck bolt that is seemingly as hard as diamond. It's stuck in a 1990 T/A and appears to be cold welded in there.

Started off bad as I didn't have a punch tool and ended up with a off center drilled hole (1/8") which broke off inside. After that all the drill bits I threw at it seemed useless... virtually no grab... sat there for an hour with full weight trying to drill it and making hardly a dent. Used some WD-40. Titanium bits, dewalts... all useless. I'm sure having to grind through the now broken off bit it just adding to the misery...

I wanted to hit it with the bernzomatic but there are fuel lines right in the way. no fire it is!

Picked up a bolt extractor set from autozone. Again, no grab. Can't get a pilot hole started, so the extractor just sits there and spins. Useless.

Next up: the Dremel. This actually destroyed the bolt quite well... but this method doesn't pull the bolt out nice and clean like the extractor tool is supposed to, leaving you with clean re-usable threads. I was able to grind about 1" deep after about 1 hour of dremeling, trying to be careful not to hit the threads. That bolt is eating up just about every dremel tip that I have. Bent rods, shattered grinding stones, bent blades. But it's at least doing something.

I've tried threading in the broken bolt piece but the hole is still a bit too narrow. Actually I think the problem is that the thread channels are filled with bolt steel. I would like to re-tap the hole to clean out the threads so I can use a new factory bolt. Does anyone know which tap bit I need to do this? Or is there something else I should try? I'm new to reading bolt sizes but thinking that the bolt has an outter diameter of 3/8" and a length of 1 1/2", but what is the threads per inch? Which tap bit do I need?

Surprisingly I found 0 threads in the search engine

GeneralDisorder

iTrader: (1)

WHOA! Hold up there wise gentleman....

You need to STOP. Take some pics so we can assess the situation and see what kind of access you have, etc.

The only recourse at this point will be carbide. You will need (probably a couple due to your n00b-ness) of these:

https://the-original-rescue-bit.myshopify.com

Then you will have to install a heli-coil (screw thread insert repair). Get YouTube certified on that before you begin. If the hole is now too great for even this option then TIG welding followed by thread repairs will be required.

GD

TylerSteez

iTrader: (3)

Yeah seems like you backed yourself into a hole and carbide bits are all that's left.

I've used masonry bits (carbide tip) to drill out hardened bolts in the past with great success. since your hole is now off center of the bolt, you cant fully drill out the broken bolt without drilling into the manifold itself and creating an unusable hole.

(skip to 1:50)
This is the method I always go to first since its the least invasive and has a good record of working for me. since you have an off center hole from your drilling attempts, that can be the perfect ledge to prop the cold punch up and whack with a hammer in the loosening direction.

GeneralDisorder

iTrader: (1)

Knocking it sideways with a punch isn't going to work with it seized in the aluminium. Very little chance anyway. That method works well on stuff that's not really corroded. Left hand drill bits usually work well also. I typically do all my drilling on broken fasteners with left hand bits as they have a good chance of grabbing and spinning it free.

Broken/rusted/stuck fastener removal is an art form. A skill that is hard won I'm afraid.

GD

TylerSteez

iTrader: (3)

whoops you're right, forgot we are talking about an aluminum intake manifold. at work all my broken bolts are in steel

gta90

iTrader: (1)

Appreciate all the replies and info about the rescue bit and helicoils. Good to know I still have some options. I'm hoping I can just re-tap the hole as I did a pretty good job excavating out the bolt. I measured the bolt threads to be 17 threads per inch. I can't seem to find a tap that is 5/16" (3/8" - 1/16") with 17 TPI pitch though. Is this a non-standard thread pitch, or perhaps the bolt threads are deformed? I'm doubting the latter.

Unfortunately the car is at family's across town... afraid I won't be able to snap pics any time soon.

Oh and yeah I tried the directional tapping when there was still a slight head sticking over the surface... no dice. Also tried vice-gripping on the little nub head, but wasn't enough to grab on to sadly.

TylerSteez

iTrader: (3)

17TPI is uncommon, I'm pretty sure the bolts for the t stat housing are 3/8-16

scooter

iTrader: (11)

If it's in aluminum, you can weld to the broken screw, build it up a bit. Then put a larger nut over that, weld the nut to the stud, Then you have something to put a wrench on, and the heat of the welding will break it free of the base metal. It's pretty easy when the base metal is aluminum. Get the nut nice and red usually does the trick

gta90

iTrader: (1)

Sounds right regarding the 3/8" - 16 tpi size... the bolt must have got stretched over the years as it measures exactly 17 TPI. Or perhaps there is a conversion factor of minus 1 when determining pitch. The bolts sure seemed over-torqued... surface gouging on manifold.

I like the welding technique. Will try to remember that one next time this happens.

UPDATE: Fixed it up finally. Dremel'd out about 1" deep, then drilled the hole using a 5/16" drill bit. After that cut new threads using a 3/8 - 16 TPI tap. Used thread cutting oil. Used shorter 1" bolts. Don't recommend you do it this way. Save yourself time and $ by starting with a carbide drill bit (maybe 1/8") and a strong bolt extractor.

Appreciate all the tips and ideas from everyone. Do not recommend using any heating methods (flame, welding) on this application as there are fuel lines right in the way. Don't want to blow your face off, set the car on fire and burn down the house all in one go.