Today I went to change out the coolant, hoses and thermostat. I went to unbolt the first one on top. It gave me some resistance, but I figured that was because the engine was stone cold and it is an aluminum housing. Well the damn head came right off. I didn't dare try to remove the other 2 bolts after that. Will this leak on me and what can I do. Generally when this type of thing happens you drill out the old bolt, but there is only about 6-8 inches of clearance before you hit the fan shroud. Any advice would greatly be appreciated. At this point I have added as much coolant the engine will take cold. I haven't started the engine yet to get the coolant flowing.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Just an idea...pull out the other bolds, remove thermostate, you might have a bit of the broken bolt sticking up above the houseing. make sure engine is warm so bolt comes off easier then take a vice grip on top of broken bolt and try to turn it. If that fails the only things I can think of is to drill it out and re tap the threads

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1996 E320
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.

As long as a part of the bolt is still sticking out, you should be able to get the damned thing out. You need to unscrew (or break ) the other bolts first and remove the thermostat house.
When the method described above does not work, you can try welding a bolt head on the part of the broken bolt that sticks out (presuming it does stick out). The bolt (and surroundings) will get warm of the welding and can normally be screwed out...

This is just one of the downsides of driving an oldie...

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

I just ran the eng. up to operating temp. and the thermo. cover didn't leak. I added more coolant as she needed it. I am a little gunshy to try and remove the other 2 bolts. The engine is warmed up, but it's raining now, so it will have to wait. From what I can see, there would be enough of the bolt sticking out to grab with with a pair of vise-grips once the cover is removed. I guess a good shot of WD-40 might of helped.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

WD-40 sucks. Get some serious penetrating oil. I had the same thing happen to me on an old Honday. Of course, my bolt sheared off just below where it threaded into the head. It did leak.

If all else fails, you could try using a stud extracting device like EZ out! Be forewarned though, this will invariably snap so make sure you have a drill with a diamond head so you can remove it!

Kuan

A pair of vice grips won't help. You've got a galvanic corrosion problem where your iron bolt is stuck in an alloy hole. The only way to cure this is to heat the bolt and get it red hot. THEN, a pair of vice grips will be able to remove it.

If you don't have access to welding equipment AND the car is drivable, take it the nearest shop and ask them to do it. Go there armed with FOUR replacement bolts and any required washers and gaskets, so that you can drive away again. It should set you back 20$ for somebody else to take care of it. Also, be sure to lubricate the bolts slightly prior to reassembly.

If you have made friends at a junk yard or other equally wonderful, slimely place, they most definitely can help.

If it holds water with 3 bolts now, it won't do so for long.

-CTH

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- cth350@gmail.com
http://www.111lakeside.com/

I would leave it at this point. Welding another bolt on is always a great idea. When I didnt have a welder, try to thread two nuts onto the stud , one at a time if you have enough of it still showing. Then tighten them together. Then put your wrench on the inside one and loosen. You may get lucky . If not, get drillin'!

I have broken a bunch of water pump studs on my 944s. A real hassle. But a necessary evil.

Good luck !

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Patrick Leber
'84 190E 2.3
'83 Porsche 944 (track car)
'84 Porsche 944 (parts car)
85.5 Porsche 944 (sled)

Rick,
Don't despair! Help is on the way. Strange, but none of the 'experts' mentioned the fact that you can buy the whole thermostat housing for around $40. No hassle trying to get the broken screw out and no trips to the machine shop. With a new housing you wind up with all new screws.
Bill Lewallen Lexington,Ky. The Bluegrass State Where the grass is really green,and so is our antifreez.

Sorry to waste bandwith , but my reply should say "I WOULDNT leave it" . Just my humble opinion.

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Patrick Leber
'84 190E 2.3
'83 Porsche 944 (track car)
'84 Porsche 944 (parts car)
85.5 Porsche 944 (sled)

Thank you for all the advice guys/gals. I am definetly not going to just drive it as is, if it can be avoided. As it sits now there is no stud sticking out to grab, it broke pretty much flush with the cover. I completely forgot about galvanic corosion. You would think that the engineers at MB would of forseen this problem. Right now it looks like I have a couple of options. Try to remove the other two and hope for the best. Then remove the broken stud. Then there is Lewallen's idea and buy a new housing. At least for time being the car is driveable, she has all the coolant she needs and all the clamps are tight. The only weak link is that thermostat cover.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Greetings Rick,

Several of the above threads provided the right info to get the job done or at least put you on the path to a repair or replacement. If you haven't ever removed the elbow before, then I doubt if it would leak if you pull all the bolts out. These little thermostats they have for these MB have a rubber o-ring seal that surrounds the thermostat and after a week or so of driving they pretty well seal to the aluminum housing. I know, it took several blows from a rubber mallet to even free mine after the bolts had been removed. You simply have a few choices as was already mentioned, but don't worry about it leaking in the mean time, it won't. I like Bill's idea of finding a source for the elbow, in case you do need it, and then remove the other two bolts and let some penetrating oil sit around the threads of the broken bolt for an hour or so, then heat it up and simply remove it with a vice grips. Make the grip tight the first time though, so it doesn't chew up the remaining stud. The easy out method will also work if you don't use a chineese made easy out, but one that was actually forged out of steel and then hardened. Like bill says, the elbow can always be replaced if all else fails, so you're not SOL on this repair. I'll trade you repairs, I'll do your elbow if you pull my IP and retime it?

Charles

I have already tried to source a new thermostat housing but couldn't find any. I don't know where he got the $40 figure from. I looked up in the "Fastlane" and well as an outfit callled "thebenzbin". No luck. I would like to get this situation corrected. The reason I am changing out the thermostat is just for a piece of mind. I don't know when the previous owner changed it last. So I look at it as cheap insurance against a overheated engine.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

Greetings Rick,

Give these folks a try out in Oregan, just follow the link. Can't see why you would need a new part, buy a guaranteed used one, for cheap and you'll have your part.


http://www.mercedesusedparts.com/116-123-126.htm#116


Charles

Thanks I'll give them a try. The weather here in NJ has been rainy and cold for the last 2 days, so I haven't messed with the car since the "bolt incident".

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member