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Broken bolt on manifold to cat pipe junction


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Where is Loren when you need him?

Are you talking about where the 2 flanges are bolted together with 3 nuts just at the end of the manifold? I am a Boxster guy and do not know about the 996 exhaust. On a Boxster it is a normal bolt. In my Boxster picture you can see that one of the bolts has fallen out when the exhaust system was removed from the manifold. PET for a 996 shows a picture of what looks like a normal bolt. Perhaps a picture? Jeff

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Yes it is similar but I cannot see the non threaded end on your pic. Mine is round and flat and looks like it was just pushed in there, ie threads start on back side if hole. When I get home I'll take a pic.. Sorry should have said..car is an 01 996 C4.

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Sounds like a serrated stud that is in fact pressed in from your description, despite the PET description, and PET has been wrong before. "Easy" to remove with a straight punch and a BFH if you have room to work although the best way is to press it out since that type of stud is pressed and not pounded in. According to PET it is a very small diameter, 8mm, and I can see how it would snap when you torque on a frozen nut. Been there several times on non Porsche cars.

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:cheers: Indeed it is very similar to that serrated part is longer though and it is

8mm dia. I do have a BFH and a punch but would it help to heat area first do you think? Also cat pipe is very squirrly not being hooked to the manifold (have mufflers off too.) I guess I will need to hold the pipe with something before giving it some love taps! Thanks agian for your help! Jim

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My picture is a wheel stud from some American car that I found on the net, solely as an example of a serrated stud, as I could not find a 996 Porsche serrated exhaust stud on the net as much as that is hard to believe.

If someone does not pipe in let us know. I have a suggestion as to how you can press the broken stud out of the flange if the the BFH and punch method does not work if there is enough clearance on a 996.

Be careful if you are going to pound against an exhaust manifold, and do not say I did not tell you so.

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Sorry to be late into this... (was working on the site)

Jeff is correct that the serrated bolt is not what is shown in the parts list. But the original bolts are the serrated stud type (at least they are on my car). If you look at these bolts they are made of some copper or brass content alloy as they bend and deform when tightened. A new exhaust nut does not even look round and it deforms and locks as you tighten it.

I agree with Jeff that if one of these is broken off the best thing to do is press it out -- you really don't want to shear off a head bolt (ask me how I know sometime... :blink:

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:unsure: So Loren will I have to take the cat pipe out to press out the bolt? I am guessing you use really big pliers to grab and push the threaded end? What would you do when the threads get to the flange face and other side is now sticking out...pull it?

Since is is soft brass heating should expedite this correct? Sorry :cursing: just really mad it was so rusted it broke should have cut it off but who knew? All the ithers came off, albeit with difficulty, and did not break!

Jim

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I think you can do this without taking the whole thing off. I don't know what Jeff's idea is but here is what I used.

I have this tool that I can't remember when I bought (but likely about the time I was breaking the head stud off my 914 :cursing: ). It looks like two flat metal bars (with a hole in the center of one) and with two thumb screws between them. I think you could do the same with a couple of c-clamps and metal bars (one with a hole and one without). The metal bar lets the bolt push through while applying even pressure on the second bar (on the bolt end) via thumb screws.

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I can't be much help as I am not familiar with the area of the flange on a 996. Need to see a good picture. If you have enough room/clearance to put a straight punch on the broken end of the stud and enough room to swing a hammer - I say give it a wack and see if you can pop it out. It is small. I have done this on my truck wheel studs which are much larger but I had plenty of room to swing a BFH.

If you have the room and clearance you can try to push it out with a c-clamp. You put a socket on the round part of the stud that is larger than the round part, and something on the broken end. With your 3rd and 4th hands you put the clamp on and tighten it. This will force the broken stud out of the flange and into the socket. This is how I replaced universal joints as a kid when I did not have the proper tools.

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I thought the stud was in the manifold flange but I can see it is in the other flange. Do it whatever way works. If you do it on a bench vise put a proper sized socket over the round end like I said. Then clamp the socket and broken end together and the stud will be pressed out into the socket.

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Well I tried the C clamp/socket idea with cold bolt and it does not budge... I left the C Clamp on there and am going to heat area and try cranking. If that does not work I am taking out both cats (As this one is the one that goes over and you apparently have to) and then going to vise whole pipe down and beat the :censored: out of it with the BFH! If it breaks I guess I will have to replace them. Any body have any ideas for aftermarket cats that give better flow that also actually pass emission tests?

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:clapping: Well I got the :cursing: out of there. Had to remove the cat pipe and heat area with torch then one whack from the BFH and it went flying.. I think I will do all of them while it is out and replace with regular old bolts and anti-seize compound.

Thanks so much for your advice

:cheers: Jim

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