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Hey guys, yesterday I was changing my thermostat on my 2003 e500 and one of the 2 screws that holds the thermostat in snapped in half. I have been trying to extract it with a few extraction kits but still seem to be struggling. If anyone has any ideas on how to get the screw out, perhaps my taking things apart, please let me know, If your idea works I will return the favor via paypal. Thank you.
the screw broken in half is shown inside the red circle
Probably you're going to have to drill the old screw out and re-tap the threads. You might even get lucky and find that the drilling releases the tension on the old screw which will then allow you to us your tap outs. Hope this makes sense.
Its a gamble but using a center punch mark the center of the stud showing deep enough that a drill bit will sit in the punch mark, remember it is a steel stud in an aluminum piece.
Using a 1/8 sharp drill bit position on the punch mark and slowly drill in line with the stud through the center punch mark. Slowly as to build up some heat in the stud, drill in 3/8 to 5/8 inch into the stud. Now with a 3/16 inch drill bit do the same into the 1/8 hole, after doing this insert an "Easy Out" into the 3/16 hole using a hammer to seat the easy out, slowly reverse the stud out while there is still some heat from the drilling.
Good Luck it will take patience and accuracy and skill to complete the operation, if possible try a larger drill bit but not large enough to get into the thread area. Use the other hole for maximum drill size then reduce to one smaller. With the heat created the stud may back out, steel and aluminum like to stick to each other, anti seize would be a good investment on the rebolting procedure, it will never stick again.
Good Luck I realize space is at a premium and will be the biggest obstacle.
You need to go buy 2 drills, a 1/8 cobalt drill and 3/16 cobalt drill plus a 1/8 rod maybe 4" long, If you can file the area circled fairly flat to see the broken bolt? Center punch the CENTER of the broken bolt! Very important!!! Secondly, slowly drill with a 1/8" cobalt drill with liquid tap or water! Drill at least 3/8" deep, you can try a removal bit but first,,, heat 1/8" rod tip almost same depth and insert in hole you drilled and let set about 10 -15 seconds. Insert extractor and tap in gently, twist out broken bolt! If not enough grip go to next step of drilling hole out to 3/16" and heat rod insert and try and remove??? If not a standard drill 1/4" should follow the hole and try again to extract. I don't know what size bolt you broke off but when you buy the 1/8" cobalt and 3/16" drills buy correct size tap. Run the tap in slowly with oil!!! do not force it in, take your time, 1/2 turn in 1/8 turn out, repeat till you hit bottom or length of bolt removed was screwed in? TAKE YOUR TIME! If you hurry you will F*#& it up and either a heli-coil will have to be installed! That requires a larger hole with a tap and a heli-coil installed the size of your bolt! It can be done but BE PATIENT, Be a tortise doing the job, you wll win in the long run!
just a FYI... once you get the old one out, if the hole is too boogered up to tap and clean up the threads... you do have enough room to drill and tap it to the next larger size bolt. you may also have to enlarge the hole in the housing as well.
I usually prefer tapping to a larger bolt (provided I have enough material to work with) over a heli-coil as helicoils have a tendency to come out with the bolt next time it's removed, and they often bring the aluminum with them.
If you DO resort to a helicoil, make sure you use plenty of corrision resistant lubricate, such as molylube or some such.
2017 GLA 250, 2011 C63 P31 (p30 w/ lsd) (in repair), 2005 C230 Sport Eurocharged, 2003 C320~sold
When drilling to use an extractor use a reverse drill bit... One that drills counter-clockwise or to the left.
If it broke trying to remove it initially and didn't over tighten it causing it to snap it probably won't come out and is seized. You can try spraying PB Blaster a few times and let it sit prior to removing.
If you must drill it all the way out use a good bolt as reference for how deep you need to go.
Good luck!
Get some JB weld and a bolt a little smaller than the broken one. "Weld" the tip of the bolt to the broken one, wait, then unscrew the whole thing out.
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