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Snapped thermostat bolt in 01 Forrester


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Have radiator seem leak so replacing it and thermostat too. I was putting the thermostat housing back on and snapped one of the bolts off. Top third of bolt broke off. Looks like this is the water pump so I am thinking probably easiest to remove water pump and easy-out the bolt or retap with larger bolt. Any thoughts, advice, or suggestions?

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Is there enough bolt sticking out (with the thermostat housing removed) to get a pair of vice grips around to turn it out? I'd try that first. But you need to check those threads, if they are damaged a new bolt may go in and strip the threads out, then you'll be right back in the same boat. If you have a tap kit this is a good time to use it.

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dont he-man on those little bolts. use a 1/4 drive tool. the torque is measured in inch-pounds. just hand tight, then snug about 1/8 turn.

 

same for the water pump and oil pump bolts. we got tiny bolts threaded into aluminum. all too often i see 'hillbilly torque' ruin parts on these cars that are serviced by old-timers whho are used to torquing coarse threads into iron

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Water pump and timing belts done less than 10k ago when I had head gaskets done. I think I just over-torqued it - my torque wrench calibration must be off. Usually I don't even bother with torque wrench. Oh well. lesson learned.

 

Hopefully a little penetrating oil and I can extract it. Otherwise drill and re-tap. Really don't want to replace an almost new water pump. And hopefully can get this done without removing timing belt and water pump.

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I pulled the housing back off, sprayed some Kroil from the top to loosen the bolt up and was able to back it out with my fingers. I also saw that these bolts are designed to shear right wear it did, since there is a taper to the threads. I suspect I need to source these from a dealer parts counter?

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I got a few from the hardware store to replace the rusty ones on my wagon. Anything grade 5 or better should work fine as long as you get something with an anti-corrosion coating such as zinc.

Stainless steel is not as good of an idea as it sounds, so stay away from that.

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The tstat housing bolts are only torqued to something like 6ft/lbs. You don't need any special hardware.

 

You need enough strength in the shaft of the bolt to overcome any rust/corrosion on the threads when trying to remove it. If you use the cheapest hardware you can get, you end up with a broken bolt.

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Stainless steel is not as good of an idea as it sounds, so stay away from that.

 

You need enough strength in the shaft of the bolt to overcome any rust/corrosion on the threads when trying to remove it. If you use the cheapest hardware you can get, you end up with a broken bolt.

 

I agree on both counts. The stainless hardware you usually find in hardware stores is 18-8 stainless which is really weak stuff. Stronger stainless alloys are prohibitively expensive to stock at your neighborhood hardware.

 

As Fairtax mentioned, anything with a corrosion resistant coating will do, remember that every other bolt on your car has just that. Some antisieze doesn't hurt either.

 

Will-

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I agree on both counts. The stainless hardware you usually find in hardware stores is 18-8 stainless which is really weak stuff. Stronger stainless alloys are prohibitively expensive to stock at your neighborhood hardware.

Will-

 

This may be true (i'm no metalurgist), but there is also the problem of galvanic corrosion of the aluminum when stainless and bare aluminum come in contact. This will rather quickly cause the bolts to seize and will deteriorate the threads in the aluminum. Makes it a royal pain to take apart later on.

It may only be certain grades of stainless, I'm not sure, but I see it all the time.

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