# Please help - Any ideas welcome



## Advisual (Jun 2, 2020)

I was working on my 2007 Buick Rendevous changing out the thermostat and I accidentally stripped out the mounting thread with the wrong bolt. I am trying to figure out a way to repair it. I had a person come over who had an arc welding setup who tried to weld a bolt to the back side of the tread but it kept welding the nut with the bolt we were using to hold the nut in place. Also the nut was not welding to the cast iron block.
I have uploaded several pics to show what a before and after look like. I also show how I was trying to mount a bolt with a nut on the back side.
Can anyone suggest a way to fix my issue?

Thanks


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## Janderso (Jun 2, 2020)

Oh man,
 I'd welcome you to the forum today but you are having one bad time of it.
If the manifold was off and you could machine the mounting surface this task would be much easier.
My thinking is, mount the manifold on a milling table, build up the area with brass rod. machine, drill and tap.
You would have to extend the arm on the knee mill so you could drill at a 90 degree angle.
Sorry, that's all I got. Fixing it inside the vehicle will be a mickey mouse job that will leak. In my humble opinion sir.


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## DavidR8 (Jun 2, 2020)

Yup, what Jeff said. I cannot see a way to fix this in-vehicle.


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## Martin W (Jun 2, 2020)

Do you have an auto salvage or wrecking yard near you. Just put a used housing on it.
cheers
Martin


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## benmychree (Jun 2, 2020)

It looks like to me that the broken part is on the engine block itself, yes/no?  If yes, I agree with Jeff, not an in the car job.


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## twraska (Jun 2, 2020)

Do you have room to make a big clamp out of two  pieces of metal and sandwich the housing in between?


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## Cadillac (Jun 2, 2020)

My first attempt would be to replace the manifold from a u pull it place. Last resort would be to weld  a stud in that hole location  probably braze it on or tig with some silicone bronze. Least amount of heat possible


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## Tim9 (Jun 2, 2020)

That’s aluminum. I don’t think brass will do it. But....like others said. Get a used one from a salvage yard. Buick / Chevy v-6 pretty damned common.  And it’s not that hard to change.

if it was a hard to find part...yeah tig aluminum and machining it ..  but that’s probably a common V-6. Providing it’s 3.8 or 4.3


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## Ulma Doctor (Jun 2, 2020)

put a fork in it, its done!

you could remove the manifold and try some of the low temp alloys for repair
but i think you'd be better off with another manifold after the expense of time to remove, repair and re-install


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## General Zod (Jun 7, 2020)

Advisual said:


> Also the nut was not welding to the cast iron block.



That's because that block is aluminum.  Check if a magnet sticks to it. 

To fix that in-vehicle would require quite a bit of skill, not to mention A LOT of amperage to puddle a huge chunk of aluminum!  Again, this kind of repair is not for someone who has just any old "arc welding" set-up.  You need a BEEFY TIG welder that has AC capability _in the hands of someone who has done this before._


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## Bi11Hudson (Jun 7, 2020)

I don't have anything useful to add, but would bring up the fact that brazing melts at around 1800F while aluminium melts at only 1400F. I had a friend (professional jack leg mechanic) tried to rebuild one of those engines. He overtorqued the manifold bolts and about 100 miles later, the crankshaft galled. Those engines are not suitable for real repairs. The bearings get out of true because the block twists so easy. Be careful. . .

.


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## Diecutter (Jun 7, 2020)

If you are down to looking for a hail Mary pass, this might work, at least for a while.  It's called a manifold repair flange. The pointed end digs into the casting while the threaded end supplies clamping force.  Could work since you are only contending with radiator level pressure.  Man, that  original tapped hole was sure  close to the edge which is why it probably failed in the first place.  I agree with the group that the only permanent repair is pulling it out and repair/replacement. Good luck.


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## RJSakowski (Jun 7, 2020)

Advisual said:


> I was working on my 2007 Buick Rendevous changing out the thermostat and I accidentally stripped out the mounting thread with the wrong bolt. I am trying to figure out a way to repair it. I had a person come over who had an arc welding setup who tried to weld a bolt to the back side of the tread but it kept welding the nut with the bolt we were using to hold the nut in place. Also the nut was not welding to the cast iron block.
> I have uploaded several pics to show what a before and after look like. I also show how I was trying to mount a bolt with a nut on the back side.
> Can anyone suggest a way to fix my issue?
> 
> Thanks


If the broken casting is indeed part of the block, this could be difficult.  Rather than trying to build up the missing piece, I would try this.  Clean up the remaining threads to be able to cradle a stud.  Place an aluminum stud in the threads and tap in to seat in the remaining thread.  TIG weld the stud to the casting.  Not as good as a proper repair but with care, could last the life of the engine.  The particular application is not a demanding one.  You just have to create enough clamping force to seal the thermostat gasket.  I would use a stainless steel nut on the stud and use anti-seize compound on the thread.  Use care in tightening.


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## dirty tools (Jun 7, 2020)

Helicoil or other thread repairs will work


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## RandyWilson (Jun 7, 2020)

It's a Chevy 3.5, which is 0.1 better(???) than it's predecessor the 3.4. The thermostat is in the lower intake manifold. The manifold is aluminum. Crap American pot-casting aluminum, not easily welded. The day may have been saved with a heli-coil or better a timesert, before the ear was broken off the manifold. At this point the only option is to change the manifold. It's a 6.5 hr job, book time.
 My question is why was the thermostat being changed? Random preventative maintenance?  Or a hail mary trying to cure overheating? These motors are VERY prone to headgasket failures.


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