1992 300D 2.5 turbodiesel. 229982 miles.

When I saw the exhaust manifold, it seemed as if one bolt (or stud) at the rear (the closest to the passenger) were missing.

I looked more carefully with a small variable angle mirror that I use to see my teeth.
It seemed that the bolt (or stud) was broken.

How can I remove that broken bolt (or stud) to put new bolt (or stud)?

You are probably going to have to take off the Exhaust manifold...
then you can try a ' stud remover' to see if that works... all depends on what caused it to break....
If that does not work you may need to drill it out... if you can't do that you may need to take the head off and have it EDM'd out...
A broken exhaust stud is one of the things mechanics hate the most...

Got that right!!!!!!!!!!!
This past week; R&R Jaguar head gasket, "sproing" removing head bolts, the #14. stud broke just below block surface.
An eight hour job turned into a sixteen hour job.
I still only get paid eight hours!
Seven drill bits and three extractors later, the two inches of threaded rod came out.
This was one of those simple DIY jobs that the owner is very glad they did not do.

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If the broken stud is left as it is, will the manifold gasket be damaged and leak?

dont fix it.
Very strong advice in this case.
When it leaks; then you fix it.
No harm in waiting.
Have a great day.

If the broken stud job is combined with head gasket job, do I save money?

Someone said that it is a lot easier to remove broken stud, when the thing is on a table rather than in the car.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

It would not be too much for the shop that rebuilds the head to go ahead and remove the stud.

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Jim

I have seen several of these on 603 engines where the stud breaks off. In many cases, the stud and nut are still present, but they aren't doing anything. No harm seems to occur. If I were you I would leave it alone until the head or motor come out of the car. Have the exhaust manifold checked/planed as necessary at the machine shop next time you remove it. The are known to warp on 603. I realize you have a 602, but they are similar (602 = 5 cyl, 603 = 6 cyl).

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Brian Toscano

If it isn't leaking.....don't touch it.
If it is......take the rest of the nuts off. remove the manifold.
Get a small propane torch and gently heat the surrounding head. (area around bolt) Turn out broken stud with vise grips. (if you can grab it)

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I had the same car, the same problem. One of the studs broke off. It was the one closest to the radiator. It broke so that there was no chance to get a grip on it. Whatsmore, the exhaust gases escaped. They could be smelt inside, also the alternator was black because of the carbon. There just was no room to use any tools to drill the stud out. Attempts to seal the leak with heat resistant silicone failed after a day or two of use. The whole head had to come off. A set of new gaskets had to be installed. The bill from MB dealer came to $400, including parts. The brighter side is that I have a new head gasket.

Anyhow, if you can't reach the stud without removing the cylinder head, you will have to remove it. Don't forget to order new gasket set before that.

Is the "heat resistant silicone" you tried but faild a kind of muffler & exhaust sealer?

I wonder why no one suggested putting muffler & exhaust sealer creme around the edges where exhaust manifold meet the engine. It can be done without removing manifold, turbo etc.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

$400 at dealer? An indi's quote was $600. Hm.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

I live outside of USA, prices are cheaper here. $20 per hour of labour (exc. tax) at MB importer/dealer. Usually $5 at indi, cash on hand. Also when you buy spare parts at MB dealer across the border you are returned the GST so you save even more. (-20%). 2 days ago I bought valve lifters for a 602 engine. 22.50 Euro each. After the purchase I found out there were non-genuine lifters available on the market at the price of $7 each. Hard to tell whether they are inferior or not, have not tested or even seen them. One way or the other, I now have 10 new original valve lifters, ready to be installed next week. At MB they said 2.5 hours of labour. Not too bad I suppose.

By the way, why is there “ticking” noise when accelerating, if the exhaust manifold gasket is leaking?

==============Exhaust gas, especially carbon monoxide, can be deadly if it enters the interior of the car. The symptoms of an exhaust leak may include a louder than normal exhaust sound, the sound of exhaust coming from unusual places on your car, a “ticking” noise when accelerating, and the smell of exhaust. However, don’t rely on your sense of smell as a conclusive means of determining if there’s an exhaust leak. Carbon monoxide has no odor. If you suspect any problem with the exhaust system, have it inspected immediately by a professional technician. Another symptom of a potential exhaust leak is a failed emissions test. A leak not only lets exhaust gas out, it also allows oxygen to enter the exhaust stream, which can be detected during an emissions test.
============http://www.carcarecouncil.org/Exhaust/exhaust_gaskets.shtml

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

[QUOTE]Originally posted by ktlimq
[B]By the way, why is there “ticking” noise when accelerating, if the exhaust manifold gasket is leaking?


No idea what that 'ticking' noise is supposed to sound like. When there is a leaking gasket there is a hole in the system, very close to where the explosions take place (unlike the opposite end of the exhaust system). This means the explosions get a lot louder to human ear. When you depress the pedal you can hear the 4 stroke system. Depending on the size of the hole this can get VERY loud. There is a flexible steel part on the exhaust that disintegrated once with my car. Unbelievable how LOUD the engine got. The cycling explosions in cylinders could be heard as on a 2-stroke motorbike. Maybe that's the 'ticking' sound.

They could have just written that with a leak the engine gets noticably louder. One advantage to gassers is that with diesel you can see the leaking spots easily - they are coal black all around.