Broken stud: Exhaust manifold - PeachParts Mercedes-Benz Forum

Ron in SC · #1 02-11-2006, 03:44 PM

The stud nearest the firewall on my friends 1990 300D 2.5 turbodiesel is broken off in the head. It appears that there is no exposed thread in the head, in other words it must have broken off flush with the head.

I've drilled into studs like this before and then used an extractor to remove, all with the head installed and the manifold not removed. I've been lucky before in getting them out. It's a huge pain to do this.

First of all is this common with the diesels? My friend just got this car and I'm fixing it up for his mother. New suspension, exhaust system and much more. Trying to make it as nice a possible.

I'm wondering if I should let somelse tackle this stud. Or might there be some new device on the market that I don't know about to get this stud out.

Brian Carlton · #2 02-11-2006, 04:03 PM

This malady is common to the 603 engine.

Check out this thread and then contact Guage and see if you can borrow the guide:

Broke a exhaust stud

Ron in SC · #3 02-12-2006, 09:09 AM

That's an interesting thread. Unfortunately the guide Guage used would not work for my application because the exhaust manifold is not lined up perfectly with the hole in the head where the stud is located.

I think there is only about 1/2 of a turn of thread exposed maybe a tiny bit more. Anyway I could drill thru the center of a 8 x 1.25 bolt with an 1/8" bit, thread that in the hole and use it as a guide to drill an 1/8" hole in the center of the stud and then use an ez out to remove. Lots of ifs here.

Important question is when the stud is installed in the head during assembly is any type of loctite used to keep it in place. If something like the red loctite that needs to be heated to remove was used I forsee it being very difficult to remove the stud with a small and brittle ez-out.

I suppose the worst case senerio would be to have to remove the exhaust manifold and whatever else is in the way and drill out the stud with a size H drill bit, which is the correct tap drill size for an 8 x 1.25 mm bolt, stud or whatever. If that didn't work a time-sert could be installed.

TimFreeh · #4 02-12-2006, 12:18 PM

Which stud broke? If its the one nearest the firewall I've got a custom fabricated tool to line up a drill bit on the exact center of the stud. I'd be happy to send it down to SC if you need it.

I ended up removing the exhaust manifold and turbocharger to gain access to the broken stud - there was no loctite on the remains on my stud. It was easily removed with a 1/8 easy-out once I had the hole drilled.

Ron in SC · #5 02-12-2006, 12:47 PM

Tim,

It is the one closest to the firewall. Is removal of the manifold required for your tool to be used?

TimFreeh · #6 02-12-2006, 12:56 PM

Yep, I ended up removing the exhaust manifold and turbocharger.

I was going to make a bushing that fit into the exhaust manifold but as you discovered the stud is not centered in the opening of the hole in the exhaust manifold. I guess this is why it breaks maybe?

You can't really screw around with this repair, the remains of the stud are steel but the head and threads are aluminum. If the drill bit walks off the steel stud (which is very likely due to the limited space) you are in big trouble.

diesel friend · #7 02-12-2006, 01:44 PM

Hi Tim, was following your thread and wondering whether you can post a picture of your tool somewhere. Cheers

Ron in SC · #8 02-12-2006, 08:27 PM

Tim,

Thank you for the offer of the special custom tool. I'll definately consider that. I'm not sure I want to do the stud repair. Taking all that stuff off just to get to the damaged stud is from my perspective a pain.

I enjoy working on our cars but only those jobs that interest me or I consider kind of fun. I've done the stud repair thing on other cars and I'd have to say I would not describe it as fun.

I'll have my friend get a price on having someone else do that repair.

BobK · #9 02-12-2006, 09:57 PM

I'm in a similar boat. Pulled the exhaust manifold off daughter's '87 300D to fix some exhaust leaks and found last stud broken. Stud is broken off below the surface of the head and has been for awhile judging by the soot on the head. Gonna look into a variable speed reversable right-angle drill tomorrow. May see if I can find some of those left hand twist drill bits. I hear they can work sometimes to coax a busted bolt out. May try warming up the head a bit too. See if I can get the aluminum to expand a bit. I really hate busted bolts.

Al Magaloff · #10 02-12-2006, 10:26 PM

This is where professionals shop.

http://www.mcmaster.com/

TimFreeh · #11 02-13-2006, 08:29 AM

Quote:

Originally Posted by Ron in SC

Tim,

Thank you for the offer of the special custom tool. I'll definately consider that. I'm not sure I want to do the stud repair. Taking all that stuff off just to get to the damaged stud is from my perspective a pain.

I enjoy working on our cars but only those jobs that interest me or I consider kind of fun. I've done the stud repair thing on other cars and I'd have to say I would not describe it as fun.

I'll have my friend get a price on having someone else do that repair.

Understand completely Ron - its not exactly a fun job and the potential for screwing up is pretty high.

I don't have a digital camera to take a picture of my tool, I'll see if I can find somebody to snap a few pictures.

I know a picture is worth a thousand words (and when I'm trying to describe something maybe a million words...) but my tool is basically a plate with three holes drilled in it. Holes #1 and #2 are used to bolt the plate parallel with the mating surface where the exhaust manifold meets up to the head. Hole #3 is centered directly over the broken stud in the head and it has a bolt welded to the plate, over hole #3. I took a piece of threaded rod and drilled a 1/8 hole in the center of the rod. You insert this threaded rod into the bolt in hole #3 and screw the threaded rod down until it contacts the remains of the stud in the head. You can use the 1/8 hole in the threaded rod to keep your drill bit centered on the stud. You will also need a right angle drill to access the stud nearest the firewall.

Thanks to MBshop member Hanno for letting me borrow a spare OM602 head that I used to make this tool - it would have been pretty much impossible to make with the head in situ.

Let me know what the repair estimate is - if it is high enough maybe I'll drive down and take a shot at it!!!

Tim

Anthony Cerami · #12 02-13-2006, 09:33 AM

I need to see a picture or two ......and dimentions. Is there somethig close by to bolt too....??
I can make a case hardened drilling jig in the shop and fed-x it to you ........

87tdwagen · #13 02-13-2006, 11:41 AM

So far the ideas already mentioned sould help in getting the stud out. Just remember to use Anti-sieze paste on reassembly. Aluminum and steel/iron do not marry well and the corrosion between the two is horrible leading to many frozen or snapped bolts, especially when heat is added to the mix such as in the exhaust manifold.

Best of luck