Exhaust manifold, snapped head bolt

[alexjcr]

I'm pretty sure I snapped a bolt from the cylinder head that holds the manifold.

I recently purchased an '87 325iC. I've been cleaning her up and fixing up a fueling problem it has. Upon further inspection and for cleaning purposes, I decided to remove the downpipes and exhaust manifold. Well the downpipes came off without much trouble. The PO had broken one of the 6 nuts and replaced it with a bolt. After seeing that, I decided to shop around and see if I should buy replacement manifold.

Then, well I kinda broke something more important. There's a picture



It's the missing one on the left on the picture below.



How bad is it and what options do I have?

[glnr13]

measure the stud, it should be 40mm. from the photo it appears that it's fine.
These studs tend to come out when you attempt to remove the nut.

http://realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=11_1047&hg=11&fg=50

if it is shorter than 40mm then you have a problem and to fix it properly you need to extract the remnants of the stud out of the head. or you could get by with a shorter stud in there and a nut but it would only be a bandaid until you fix it properly.

[uturn]

Looks like you got all of it out. Order a few more studs and extra nuts so you can redo the gaskets. You'll need to double nut the stud to install it and there really isn't enough room with the manifold in place. Be sure to use a universal to keep socket square and not round out the nuts.

[alexjcr]

I took some more pictures with measurements.



I guess that's all of it. It's over 40mm. I guess lucky me.



And the cylinder head side doesn't seemed to be snapped.

Sorry, but can you dummy-fy those instructions on how to put the new studs in. I'm mechanically inclined but I've never been this involved with engine parts. Usually, I stick to exhaust, intake and suspension parts but nothing really touching the block.

Btw, thanks everyone for your help!

[glnr13]

Get the studs from Ireland engineering, they have an Allen at the head. Use antiseize when reinstalling. It's recommended to chase the threads to clean them up in the Bentley but it's hard to stay square and not destroy them at that angle.

[AndrewBird]

You might have stripped the threaded hole out in the head. Be prepared to heli-coil them once you get the manifold off.

[Delta]

This happens all the time when removing manifold nuts from an aluminum head. I'd bet that the threads in the head are fine, just bolt her in when reinstalling the manifold, or get all new studs and nuts. Done.

[alexjcr]

The stud did come off straight out. I doubt I stripped the threaded since I haven't seen any metal pieces come off, but I will check once the manifold is off. I'm just hoping that if the other studs do come off, they come off clean and whole like this one.

So I'm thinking that before I put new ones in, I should blast the hole with some compressed air just to make sure there isn't anything in there and look to see if the thread is intact. Is that enough? I'm thinking about getting IEmotorsport replacements since the installation seems like a breeze with an Allen key. Any thought? Oh, and then applying some anti seize when I go put the nut on? Is that a good plan?

[jalopi]

Is it just me or does that stud not look broken at all? Looks like a normal tapered end to me.

[Jaxx_]

Is it just me or does that stud not look broken at all? Looks like a normal tapered end to me.

You might have stripped the threaded hole out in the head. Be prepared to heli-coil them once you get the manifold off.

I agree with Andrew, I think you stripped the threads. The stud looks just fine.

[jalopi]

IMO slap a new stud back in there and don't fuck with the rest of them until you absolutely have to. Removing broken studs is a major PITA and breaking them during removal isn't too uncommon on old ass cars like ours. Some unlucky people have to remove the head to get broken studs out... you don't wanna be in that situation.

On a different note, you can get stainless steel nuts & studs from McMaster Carr for slightly less than what IE wants for their set. IMO stainless is the best option for most applications

[alexjcr]

Against all suggestions, I decided to take the manifold and stud/nuts off. With a lot of patience and a careful hand, I was successful at take all studs off with no problems. All studs are the same length and as far in as I could look (first two cylinders) the stud holes in the head appear to be in great shape with an intact thread. No snapped pieces! :) :) :) I was so happy and proud of myself. Like I've said before, it's my first time tackling the cylinder head.

Here's a picture of the cylinder head with all studs off. I'm still cleaning the exhaust side of the head. I got new new manifold gaskets, new studs/nuts and a used pair of non-rusted manifolds all for $90. Not bad I think.

[alexjcr]

I bought the Ireland Engineering stud/nut kit and installed it without a hitch.

[e30vert]

You had a question earlier on about how one double nuts a stud to install it. I realize that it is no longer an issue as you went with the style that allows an allen wrench to be used in the end.

Anyway the idea behind double nutting is to put a nut on the stud and hand tighten it fairly far down the stud with enough room to then thread another nut onto the stud right behind (or on top of) the nut you just spun on. Then you secure the bottom nut and tighten the top nut against it. Causing them to "sandwich" together - see pic





From there one just starts the bottom of the stud into the threaded hole and places a wrench or socket on the top nut and turns that nut only. This will cause the stud to rotate into the threaded hole until torqued to proper specification.

This is also helpful for removing studs. Its a great technique that can be applied to many mechanical issues.


Its really common to have one or more studs spin out when removing the nuts from the exhaust manifolds/ downpipes. Heat combined with dis-similar metals causes this. Using antisieze (silver based) will provide a "buffer"between the steel of the stud and the aluminum of the head and lessen the chances of this happening in the future.

[scoobydo]

are these nuts not pinch nuts? These are anti vibration/heat that dont back out with the thermal stresses in this area. Normally found on turbos. Note they are single use as the top part of the thread is deformed to create the locking action.