I was changing the short bypass hose and twisted off one of the 13mm bolt heads that attaches the thermostat housing to the block the other is still ok, I think. I started soaking a month ago with penetrant. My question is, it looks like the bolts are at least 1" 1/2 long. If I continue to remove the intact one and it does break off would it be possible to use vice grips to remove the bolts which should be quite long. Unless the one breaks off at the head. Help please.

This has lots of good answers in the archives... check there first..... better answers because they had the advantage of time... lots of views and suggestions....
this is a regular issue....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Do not attempt to drill unless you have removed many broken bolts in the past. Many home fixes can lead to a larger mess that is more difficult to repair.

Stuck bolts usually break off flush with the hole so there won't be anything left to grab.

DO NOT use a tapered easy out, they are neither easy nor regularly take bolts out. Straight extractors are made be Ridgid, these allow you to turn the bolt in both directions, this allows you to work the bolt free. Remember, any bolt extractor is going to be weaker than the broken bolt due to it's reduced size even though the extractor is hardened.

For the existing bolt, I'd gently turn it to to see if it turns. If it binds up, drill the head off, remove the part then with vise grips and penetrating oil work the bolt back and forth until it spins free.

X20 way worse shape than you start at..

If you do drill.... a Left Hand Thread drill bit a little less in diameter than the start of the threads on the bolts takes all the pressure off the threads... and is trying to move it the way it needs to move to unscrew it anyway... I love this method when I have the proper size bit..
Discussed well in the archives....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I shouldn't need to drill, the head broke off so I believe there is at least 1"1/2 to grab on to. When/if I remove the other one as long as it breaks at the same place I should have enough material to use vice grips. I'm still soaking. Hopefully the one that hasn't broke will unscrew.

Try heating and cooling it a few times if you have a way....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

My favorite method is to weld a new head on.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

These bolts are steel into aluminum. they corrode. I have gotten many of them out by just very gently wiggling them one way then the other until the work loose. I have gotten them out with half the bolt eaten away this way. Of course you have to replace them once out.

If you can't get the broken bolt out these housings are fairly common so you can buy one and install it. there are several different versions so if you want to buy a used one you'll want to include the part number.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I have a Ridgid drill & electric impact that came with a lifetime device and battery warranty. Very nice stuff.

How much experience do you have with the extractors? They would be very handy if they work well.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Every time I try to use an EZ out I broke it off in the hole. Then you have the problem of getting the EZ out out. Compounding the problem is that your parent material is aluminum (soft) and the Problem bolt is steel (hard) so if you are drilling it it'll be tough to keep it on the problem bolt. Pretty good chance you'll end up needing a new housing.

That's why it is so important to go very very easy on the initial removal to avoid breaking them off.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I broke ONE of mine when I was doing this. I got lucky and it was the one that goes thru the housing so I just drilled thru and installed a nut on the bottom. Piece of cake. I got the other one off with heat - oxy-acetylene type heat.

Dan

I think I may have been unclear on which bolt(s) are stuck. It's the one's that go through the housing into the head, not the one's that house the thermostat. I was trying to be careful. Yesterday I twisted off the other one, I have been soaking in penetrating fluid and wiggling, it's kind of loose, but it looks like the bolts are still frozen to the housing and seem to be loose at the head. I'm going to try an ez-out which I'm sure will not be easy. I do have good access to the bolts. I guess cutting off is my last resort. Should have left well enough alone.

Like the guys said, start with a LH drill bit. They aren't too pricey and are well worth it. Most drill motors these days (maybe all) have a reverse rotation feature.

Dan

I hope this picture helps me describe which bolts are stuck. I will pick up a set of LH bits today. Again thanks for the advice.

See whether you can remove everything else off that piece then slide what you're working on off its bolts. You don't have access to the frozen threads in the current configuration. I'll have Togo look at mine

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.