Thermostat housing bolts broke off 4.3 sonoma

I have a 2001 sanoma. Both bolts broke off thermostat housing. I tried soaking with wd-40 then used a bolt extractor on one and it just stripped away the hole I drilled for it smooth. I don’t know what else to do. They broke off flush so I cant get them off with clamps.

Can you show an image of your dilemma?


In the second picture you can see where I drilled in already to extract it. The bolt snapped about half a centimetre from the bottom. When I stripped out the hole I chiseled the bolt down so I could make another attempt.

Do you know anyone with a MIG welder that knows how to weld?

If not, I recommend the vehicle be towed to a shop where a tech knows how to do this.


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Or drill out the rest of the bolt and re-tap. I did that once with a broken strut bolt. Pain in the a$$ but worked .

You need to drill a lot deeper than that, at least 1/2 inch. I prefer to drill all the way through the bolt so that penetrating oil can reach the bottom.


I have found that using left hand drill bits has virtually eliminated the need for easy outs. Starting with a small bit and working up to larger and larger bits works best for me.


As mentioned those are nowhere near deep enough. You have to be careful, you don’t want to go too far and compromise what’s behind them, like maybe the water jacket. I prefer having the new, OEM bolts on hand so I can tell how far in they go and put a piece of tape on the drill bit to avoid going too far.

WD40 is only slightly better than putting water on them. It is a poor penetrant compared to B’Laster PB or Deep Creep.

I have done the weld a nut thing. It failed me once on an exhaust header bolt. The bolt just broke off deeper in. In that case I had to drill perfectly center and then re-tap the hole. Fun to do through a wheel well. Otherwise, it is a good way to approach these.

I hate easyouts. They create more problems for me than they solve. I’m always cringing as I turn them, just waiting for it to fracture and create a bigger mess. A left hand drill bit is better initial choice than easyout IMO.

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How long wold you let those penetrating oils set?

I did originally. I dont think it was quit half an inch. It broke off

My bolt extractor set has left hand drill bits but the set is from Matco, not Easy-Out.

If I used a left handed drill bit should I attach it to an impact wrench?

NOOOOOOO, you should never use an impact wrench for this procedure. The initial force is too great and there is little control of bit placement.


No. Do not use an impact wrench to turn drills.

And Matco drill bits are OK. I have an accumulation of dozens of left hand bits of various brands including Matco and Snap-On and even Harbor freight. Left hand bits are sold as a set with easy outs or without. My best results came from using oil to keep the bolt lubricated and alternately pressing hard and backing off slightly while paying attention to the action of the bolt which has always eventually turned slowly and then quickly upward and out.

I am surprised that the bolts didn’t rotate downward and out the bottom. It is my experience that thermostat bolt holes are threaded through the intake on most domestic vehicles. But apparently yours aren’t


Sorry, I use easyout like kleenex. We buy puffs but call them kleenex. I’m not sure which bolt extractor kits I have but not likely to be easyouts. Some from my Dad who was machinist/tool & die, some I bought over the years…

Just my 2 cents, but I hate most bolt extractors of any sort. I generally drill a tiny hole down the middle of the broken bolt. Then I keep increasing the drill size until the hole is almost to the threads and that seems to relax the metal quite a bit.
In the rare event the bit wanders and boogers the threads up I just tap to the next size up for an oversized bolt or use a step-stud.

That is followed up with square flute extractors; the only ones I have a reasonable amount of trust in and none of which have ever broken on me.

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Thanks for the tip.

No, just a regular, reversible 3/8" drill.

I’m not sure my drill has enough torque. It’s a dewalt dcd711