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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
You can drill a smaller hole in the middle of the broken piece. First you'll need to use a center punch so the drill bit does not wander. You can then place a screw into the hole with some locktite, and after it sets turn counter clockwise.
I've never had much luck with extractors. I think if the screw is stuck enough to break, the extractor usually won't budge it. Drill it out and helicoil it maybe. Take a small nail or drill bit and insert it in the other hole and see if you have enough depth for the tap for the helicoil to work.
My machinist friend swears by reverse pitch drill bits. He says just drilling it will get it to start moving.
+1 for reverse pitch (or left-hand) drill bits. Screw extractors often don't work because to gain a 'bite' they are wedged in and push out from the hole you drill. All that does it make the already stuck bolt lock in tighter
+1 for extractor. Use a good version that requires drilling a pilot hole...not the cheap versions. This should get that out no problem. Take your time...don't rush it.
+1 on the above suggestions. Priority is to keep the hole centered. If you do damage the threads, minor damage can be repaired using a tap, major damage would require drilling a larger diameter hole and installing a Heli-coil. Not difficult, we use them all the time in aluminum housings we machine at work. If the re-worked hole is slightly off-center, you may need to enlarge or slot the hole in the thermostat housing.
The chance you may remove it if you cut a slot inside the broken bolt head, and then use a flat blade screwdriver. It wont hurt if you cut in the casting you have lots of metal there. Wish you good luck removing it.
Or like posted a good puch and get a good starter in the centre. If the broken bolt is hard try a small rawplug drill bit.
Reminds me of the time i snaped off outlet manifold exhust bolt.I made a small plate with two holes in ,with the same dim holes as the the part that goes on there, and used the bolt on the other side that was in good condition to clamp it to the head ,then drill down the hole into the broken bolt .This will keep your drill in the centre and keep it there while you drill it out. I can send a picture of the jig i made if you need it as some idea. Try and get some diesel in the thread and leave it over night it will help you remove it.
Use a small center punch with sharp point. Make a dimple in the center of the broken bolt. Use a very short center drill with small bit size about 1/8" This will not flex and move around when you dry to drill a start hole. Then the left hand drill/extractor to fit into the hole with the center drill. I have done what you are doing and it is a !#@#%@ you fill in the blanks. What I have now learned is to give the bolt a sharp rap on the head with a hammer to break the threads loose for it to come out. I had the same problem on my 7.3 diesel. Hope you don't have to start taking things apart.
Actually the video shows exactly what I was saying. The short drill they use IS a center drill.
An alternative method is to weld a nut to the broken off bolt with a mig welder. Then just put a wrench on the nut. The heat during welding helps break the corrosion. Also, it's a good excuse to pick up a welder, even a cheap one. I might add that trick only works when the material that the broken bolt is in is not the same as the bolt (eg aluminum or cast iron when you have a steel bolt).
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