While removing the 17+ nuts from the exhaust manifold of this 1987 300TDT/603 engine, one of them shears off cleanly right at the manifold. Never fails, there's always one in every crowd. The manifold is almost off entirely. My question is, How do you get that broken off stud out? I have a good assortment of right-hand drill bits and left-hand drill bits and a set of easy-outs too. I never know though if you should start drilling with a conventional right-handed drill bit partially and then use a left-handed bit. Or do you just start right in with a left-handed bit and then an easy-out, or just keep drilling with the left-handed bit. What does everyone else do? I haven't been having much luck with the left-handed bits though lately. They seem to botch everything up. TIA.

i would
NEVER

use an easy out.

they always break for me. i would drill it out with a bit slightly smaller than the part of the bolt that is left after cutting the threads on. center with a center punch first. then after drilling, run a tap in the size of the stud going back in.

you have to be meticulous, cautious and careful. so dont do it if you feel in a hurry, tired ,hungry or drinking beer.

good luck.

tom w

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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.

So when do you use an easy-out? I shouldn't use my left-handed drill bits then?

this is pretty good advice, especially that about the concentration. Be comfortable, have proper light, no kids or wives nearby, no music even. Personally, I swear by the use of left hand drill bits. Heat the area and apply a good penetrant like PB blaster. Center with a center punch first, then use a center drill to get the hole dead centered. Then, use larger bits until as Tom says, you get to the minor diameter of the stud (no more) I've never used a tap without having all of the stud out of most of the open end of the hole. Usually, the stud screws out before you get there, but if it doesn't, the remaining material is like a rusty spring that can be picked out.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

This has happened several times before.

Check out the posts from guage. You might be able to borrow his tool.

Broke a exhaust stud


exhaust manifold flex pipe turns into HUGE project

no experience with left hand drill bits but they sound great.

tom w

__________________
[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.

The good thing about guage's tool is that he made a piece that fits in the manifold and keeps the drill bit centered. Once you've drilled it you can then use an easy-out. The studs really aren't that tight so I don't thing you'd break one but do what's comfortable for you, not necessarily what some person says over the internet.

Thanks
David

P.S.
Walgamuth, I'll be going to Purdue this weekend to meet up with some friends. I'll keep my eye open for a Benz.

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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I am a machinist. The first thing you must do is allow a penetrating fluid to soak down to the threads. The stud broke because it was corroded and had seized up. With this in mind. There are a number of ways I would get it out. I would first drill a pilot drill hole as close to dead center as possible. I would then drill for an easy out but never would I attempt doing this unless that stud had soak throughout the night. If the ez out doesnt work. I would drill to a size smaller than the hole that the threads require. And then I would collapse the shell containing the threads inward. Make sure you keep a magnet nearby so to collect shavings. But I stress go and get penetrating fluid first chances are after a good overnight soaking will loosen them up...I have used this time and time again. If the threads get damaged try to install a heli-coil thread insert back but be careful since this is not an item most have used on a regular basis..Good Luck

I don't envy you on this one as when I had a similar issue (last stud going aft stripped thread) my engine was out of the car and made very easy to access the issue.

All that I can add here is that I drilled the hole out to tap for a heilicoil and this worked. I was able to re-establish a new stud and apply enough torque to the new stud to make the seal. I say this because the actual heilicoil re-thread was little more than 3/8 to 1/2 inch deep and was reluctant to apply the required torque for fear the heilicoil would pull out, and so I didn't. I applied a minimum of torque, hopefully just the amount to do the trick and it has never leaked exhaust since!

I finally got the entire exhaust manifold off the car. With that, I noticed that this broken stud was actually longer than I thought. I had about an inch sticking out to put a stud extractor on it. I carefully turned the extractor only to have the stud break again. Now the stud has sheared in three places, this last piece being the final section flush with the engine. Lovely. In order to get a drill in there, I have to remove the turbocharger. This is turning into a Chinese puzzle... and I only have one shot to remove this stud.

While removing the entire exhaust manifold on this 1987 300TDT, the stud on cylinder #2 snapped off with very little force. The gasket was black at that same area which indicated a leak which also meant intense heat escaping which over time destroyed the stud. I drilled that one out carefully and retapped the hole carefully and thought I was done. I just discovered tonight that the stud closest to the firewall - the worst one, also snapped. I obviously didn't even notice that one until reassembly tonight. I nearly crapped.

I went out and bought a right-angle drill and slowly drilled out the remaining stud. I worked my way up from a 1/8" bit. With the stud out, the threads were destroyed or close to destroyed. I tried retapping the hole. Apparently, the tap must have walked or something. It ended up not going in straight and ruined any threads in that hole. Of course space is tight, taps always have a square head for some reason so you can't use a 1/4" drive hex socket for better control, and the device they give you with the tap set is too big to use in the confined area. So, I had no choice but to use a very small crescent wrench and this tap. The whole thing is a total loss, the stud won't even bite initially to start turning inwards. It turns slightly, gets stuck, and then you can just pull it out with ease. Don't know what to do... Using a tap in that area is a bit**. The engine is at a 75 or 80 degree angle, you can't see, you have to turn it with a crescent wrench, the tap walks or wanders and ruins the hole. I'm tempted to use some high-temperature exhaust paste on that entire area at reassembly in place of the stud to form a seal. I knew this would happen, reconditioning one stud hole is pure luck, two of them just isn't possible. Any ideas? SERIOUS RESPONSES ONLY.

When this originally happened, I recommended that you contact gauge and get the tool that he designed for this express purpose. It keeps the bit centered so that you can accurately drill it out. It has bailed out a couple of us already.

But, to no avail.

The tool still might help with your current situation, which is going to involve drilling the hole oversize and tapping it for a helicoil.

The only other option is to remove the head. Clearly, it's the worst scenario.

I forgot that I bought a Snap-on kit which supplies you with Ridgid-brand drill bits and easy-outs. The kit also has centering "bits". I found the correct sized centering piece, put it over the exposed stud, and drilled away. It basically drilled right through the center. The problem happened with the retapping. I've never used a Heli-coil and I'm told they're not easy to use. Much skill required, and the necessary Heli-coil brand tools too. This sucks. I read the links to other threads and everyone with a 603 has had the same stud fail, the one closest to the firewall. It just snaps off like a twig.

Why can't I retap this same hole in question with a M10x1.50 tap? I have a M10x1.50 bolt that I could use. The exhaust manifold holes are just large enough to accommodate M10 studs/bolts. I don't have any Heli-coil products, nor do I have time to insert new threads myself, I'm under a time constraint.

are in a pickle. it is an expensive thing, this benz head. you need it done right.

if it were me, i would pull or trailer the car to a good machine shop and prevail upon an experienced machinist to to the dirty work on putting in a heli coil for me. the charge will be less than you think and it will be done right. no criticism of your skills intended, but this is a very difficult thing to do.

good luck.

tom w

__________________
[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.