Exhaust manifold broken bolts

Tiny
SIRJR
  • MEMBER
  • 2005 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 196,000 MILES
This was our vehicle originally, our son owns it now. Cracks developed in the exhaust manifold. He was able to remove the manifold; however, numerous bolts were broken even before the removal. Can you recommend specific extraction tools, techniques, insight he can use in removing the studs in the block on this specific 4.2L six cylinder engine?
Thank you,
Steve
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Wednesday, December 18th, 2019 AT 5:29 AM

21 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good morning,

Can you upload a picture of the broken bolts?

As far as removal there are a couple of possibilities.

1. Drill out the bolt and retap the hole to spec.

2. Heat up the head and try using vice grips to remove the broken pieces.

3. Drill out bolts and use easy out tool to remove the broken bolt.

4. Weld a stud on the broken piece and heat up the head and try to remove.

Roy
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Wednesday, December 18th, 2019 AT 8:13 AM
Tiny
SIRJR
  • MEMBER
I will have my son send pictures. Thank you.
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Wednesday, December 18th, 2019 AT 10:07 AM
Tiny
SIRJR
  • MEMBER
Also, it is a 4.3L six cylinder. (Previous typo).
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Wednesday, December 18th, 2019 AT 10:11 AM
Tiny
ASEMASTER6371
  • EXPERT
I look forward to seeing the pictures.

Roy
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Wednesday, December 18th, 2019 AT 10:23 AM
Tiny
SIRJR
  • MEMBER
Is there an e-mail to which I can forward pictures to?
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Friday, December 20th, 2019 AT 4:06 AM
Tiny
ASEMASTER6371
  • EXPERT
You can upload them here to this post.

Roy
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Friday, December 20th, 2019 AT 4:13 AM
Tiny
SIRJR
  • MEMBER
Here are the pictures:
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Friday, December 20th, 2019 AT 6:42 AM
Tiny
ASEMASTER6371
  • EXPERT
I only see 2 broken bolts.

The one with the easy out, did you heat up the area with a torch to see if you can extract it?

Roy
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Saturday, December 21st, 2019 AT 5:03 AM
Tiny
SIRJR
  • MEMBER
I know he hadn't used any heat in trying the extraction. Could you explain the correct procedure using heat to remove the broken bolts in the block. Thank you.
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Sunday, December 22nd, 2019 AT 12:46 PM
Tiny
ASEMASTER6371
  • EXPERT
You need a torch and heat up the area around the broken bolts. The aluminum will expand and release the bolts so they can be extracted.

Roy
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Sunday, December 22nd, 2019 AT 12:49 PM
Tiny
SIRJR
  • MEMBER
Thank you for your response. My son is currently en-route from Michigan to Florida (where I live). I will show him your information. I am planning to go up to Michigan next month to help him with this project. I will get back to you either tomorrow or Tuesday, the latest. I greatly appreciate all the input you have given me. Thank you.
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Sunday, December 22nd, 2019 AT 1:14 PM
Tiny
ASEMASTER6371
  • EXPERT
You are welcome.

Always glad to help.

Roy
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Sunday, December 22nd, 2019 AT 1:17 PM
Tiny
SIRJR
  • MEMBER
Finally able to sit in front of computer. We will heat the area up first as you stated. Regarding drilling out the center of the broken bolt, should we use a left drill bit instead of the standard drill bit? If so, where would you recommend to purchase? Regarding bolt extractor; what brand should we purchase, as I do not want to purchase Harbor Freight quality for this job. Also, do they make short versions of bolt extractors as the bolt closest to the firewall does not give us a lot of working room. All your recommendations are welcomed. Thank you, Steve
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Friday, December 27th, 2019 AT 5:18 PM
Tiny
ASEMASTER6371
  • EXPERT
Use regular drill bits. I found the ones made by MAC tools work the best.

The easy outs are left threaded for removal once it is heated up.

Roy
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Friday, December 27th, 2019 AT 5:29 PM
Tiny
SIRJR
  • MEMBER
When searching for a quality extractor I am coming across two types;spiral screw extractor and multi-spline screw extractor. Do you recommend one over the other?
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Sunday, December 29th, 2019 AT 8:12 AM
Tiny
ASEMASTER6371
  • EXPERT
Spiral works the best.

Roy
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Sunday, December 29th, 2019 AT 8:27 AM
Tiny
SIRJR
  • MEMBER
Should the heat be applied prior to using the drill bit as well, or just prior to using the spiral bolt extractor?
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Monday, December 30th, 2019 AT 4:41 AM
Tiny
ASEMASTER6371
  • EXPERT
Just when you are going to use the extractor.

Roy
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Monday, December 30th, 2019 AT 4:51 AM
Tiny
SIRJR
  • MEMBER
Conclusion and update. We were unable to remove the broken exhaust manifold bolts with the head on the block. We had to remove the head from the block; unfortunately, 13 of 14 head bolts snapped. This was even after "shocking" the bolts with a hand impact driver. In drilling a pilot hole with a left drill bit to use the bolt extractor, the broken ends of the bolts all screwed out just using the reverse drill bit. Two of the broken head bolts came out easy; the two we tried to extract on the vehicle wold not move, even with heat. We would up drilling them out and used a heli-coil kit. After bolting the head back to the block, we put the gears back onto the cams and everything lined up perfectly and the cam cover was re-installed. I had to leave to return to Florida at this point. My son bolted the new exhaust manifold and connected everything else that had to be removed. Four days after I left, he faced timed me as he was going to start the vehicle. It started up perfectly, not one trouble light ( check engine, etc.) Came on. He drove the vehicle a mile that night. That weekend he drove it approximately 35 miles with out any issues. The oil (and filter) was changed twice. The vehicle has approximately 350 miles on it since and is working great. He is looking forward to passing the 200,000 mile threshold this year. Thank you for your insights to this project; I'm appreciative for 2CarPros!
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Thursday, February 6th, 2020 AT 2:06 PM

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