Stupid Thermostat Housing Bolts Sheared off!! - PeachParts Mercedes-Benz Forum

pawoSD · #1 12-05-2007, 09:03 PM

I am out in the garage currently working on removal/replacement of the thermostat on our '83 300SD (my dads) and the two upper bolts broke off while loosening them...I even heated the housing forever with a torch....didn't help, even with lots of penetrant. Bottom bolt cracked free and was able to be finger loosened. Why are the upper ones so stuck??? Its crazy!! Now I have to halt everything and order new bolts from the dealer before I can even finish this.

Now I get to try removing the "stumps" from the two upper bolts with locking pliers or something....they'd better come out, I am going to heat the daylights out of them.....

nhdoc · #2 12-05-2007, 09:12 PM

You don't need to order bolts from the dealer, just go to lowes or home depot and get some - IIRC they are 7mm, but bring the old ones with you and check the threads on their gauge, then just get ones of the right length. They are standard metric threads. Use anti-seize on the new ones so you won't face this again next time.

pawoSD · #3 12-05-2007, 09:37 PM

Quote:

Originally Posted by nhdoc

You don't need to order bolts from the dealer, just go to lowes or home depot and get some - IIRC they are 7mm, but bring the old ones with you and check the threads on their gauge, then just get ones of the right length. They are standard metric threads. Use anti-seize on the new ones so you won't face this again next time.

Are you sure? Are they a specific hardness or anything that would matter? I suppose we could go look for some....probably a lot cheaper that way too.

I got the stubs out by applying the torch the entire time I was loosening them with vice grips....crazyness. It appears in looking at the old bolts, that some genius used a lock-tite or something on them at some point! Gah! I will be using anti-seize.

unkl300d · #4 12-05-2007, 09:46 PM

There was a former thread on this same issue.
It advised against using a particular color of loctite. Red or green.

Yeah, use anti sieze !!!!

toomany MBZ · #5 12-05-2007, 09:51 PM

Sorry to hear about it, had the same thing on my water pump housing.
There should not be loc-tite used, I'm also thinking no need for anti-seize.
As far as the bolt strength, don't know.

engatwork · #6 12-05-2007, 09:57 PM

Like nhdoc said - you should be able to find those fasteners at a local supply house. Don't feel badly, I have experienced the same thing. You may end up having to remove the housing to get the broken fasteners out.

tangofox007 · #7 12-05-2007, 09:58 PM

Quote:

Originally Posted by toomany MBZ

I'm also thinking no need for anti-seize.

You might want to study up on dissimilar metal corrosion, as in steel bolts in an aluminum housing.

toomany MBZ · #8 12-05-2007, 10:03 PM

Quote:

Originally Posted by tangofox007

You might want to study up on dissimilar metal corrosion, as in steel bolts in an aluminum housing.

Maybe that was the problem to begin with, thanks for the heads up.

pawoSD · #9 12-05-2007, 10:32 PM

Yeah it was probably the dissimilar metal corrosion. I was worried about it before I began. However, I got all the stubs out, and its all set and ready for the new bolts that we'll get at the hardware store tomorrow. Then it will be all set.

My car needs a new t-stat too though, so it is next.....hopefully it goes ok. I am getting spare bolts for mine as well as a new can of MAPP gas tomorrow. My propane bottle ran out on this one.

Diesel240D · #10 12-05-2007, 10:36 PM

I would use stainless steel bolts

cnev300d · #11 12-05-2007, 10:37 PM

Oh man, I happened to break these very same bolts. Luckily for me, I did it on a junker at the junk yard! I was surprised at how easily they broke off!

tangofox007 · #12 12-05-2007, 11:05 PM

Quote:

Originally Posted by Diesel240D

I would use stainless steel bolts

Stainless and aluminum is not a good combination. I would recommend against it.

nhdoc · #13 12-05-2007, 11:06 PM

it is due to dissimilar metals...use anti-seize and all will be well in the future. Never use any loctite on them!

Caduceus · #14 12-05-2007, 11:17 PM

A really good habit to get into is replacing every bolt you take off. I have done that from a fastener supply house with pretty much every bolt I can. My dealer wanted $3 per bolt for my oil pan bolts, and they were only grade 8.8 EVERY bolt that I do replace I use 12.9, the most expensive ones yet were still only .29 cents each......why not..

82 300d turbo

rg2098 · #15 12-05-2007, 11:34 PM

Did the same thing with the 16V. Ironically I was able to remove the studs very easily with a pair of pliers. Anti-Seize is always a good way to go in these situations. Standard hardware store bolts will be plenty good enough. The new shiny bolts even look good!