Catalytic converter bolts/studs

[Stefan]

I am trying to replace the exhaust headers on my 1999 Boxster (w/3.4L engine). I have all of the parts including fresh bolts to connect the header to the existing catalytic converters (3-bolt triangular connection). However, the existing bolts/studs are corroded. So I can't tell if they are welded on or if they are removable.

On the parts diagrams, the bolts seem to be separate parts (part #23 in this diagram)

I think the diagram is wrong for my car since my car has separate headers and cats.

Is there a way to remove these studs? One is broken and they are all corroded. I really prefer to replace them if possible.

[Stefan]

One other note: the bolts/studs have rounded heads so I suspect they are supposed to be built in. If anyone has any tips for removing them anyway, I am all ears.

[Duster]

One other note: the bolts/studs have rounded heads so I suspect they are supposed to be built in. If anyone has any tips for removing them anyway, I am all ears.

When I replaced my Catalytic converters with bypass pipes on my 2000 Boxster 2.7, the bolts are wedged into 3-bolt triangular connection. I sprayed PB Blaster pentrating oil on both sides of the bolts and let it soak for a couple hours to loosen the bolts. Then I used a mini-sledge hammer to pound out the bolts. However on the stubborn bolts, I heated the bolts with a propane torch and used the mini-slege hammer to pound out the bolts from the 3-bolt triangular connection. I tried a regular hammer first, but it didn't have the weight behind it to pound out the bolts. Unfortunately I had to make a couple trips to Home Depot to buy the mini-sledge hammer and then the propane torch.

1. I would recommend soaking the bolts with either WD40 or PB Blaster pentrating oil for a couple hours.

2. Heat the bolts with the propane torch

3. Use a mini-sledge hammer to pound the bolts out.

*** Wear mechanic gloves to protect yourself from the heated bolts (propane torch) and scrapes from the exhaust system.

[Chuck Jones]

Some guys will soak the bolts with PB blaster for days before they attack the bolts. Your worst nightmare is hearing that "snap" as you shear off a stud. I think Nathan from the UK uses a nut splitter and just splits off the nuts rather than go thru all the trouble of heating, pounding, and PB soaking. Since you're going to be using new nuts anyway, I think the idea of using the splitter makes a hell of a lot of sense....provided you can get a splitter in there. He's posted a couple threads on the subject...you might try a search....I went out and bought a set of splitters, but havn't had to use them kuz the bolts came right off without much fuss.

[RFM]

Before you start with a hammer, remove the Lambda probes , they don't like shocks.

[Tool Pants]

Studs.

[dcporsche99]

Studs.

Hi,

I did the performance header install last year and IMHO the best & most practical method to take them off would be to heat them up with a torch. Those studs are heat pressed and I could have PB blastered them until I was blue in the face and I had to put my hands up and bring my ride to my Porsche mechanic who took care of it in a couple of minutes.

Here's a link to my install and the challenges that I went through:

http://986forum.com/forums/showthread.php?...=header+install

(You might have to sign in to read the thread).

Hope this helps you out! I did have fun despite the frustrations of the install and the CELs that came on afterwards.

Keep us posted!

-Dana

[Stefan]

All good and valuable ideas. I was definitely thinking of removing the O2 sensors before hammering.

Dana, you said that your Porsche mechanic took care of those studs in minutes. Did he heat them up with a torch an nail them with a heavy mallet? (Because that is my current plan) They don't look like they're going to give in without a fight.

BTW, nut cracker...sweet! (Sorry, couldn't resist)

[RFM]

Tighten the flange in a vice and you can hammer the stud out in one move, even without heating, take a heavy mallet.

[dcporsche99]

Hey Stefan,

Actually, he just heated each one of them up and used a vise grip ---gave it a good strong twist and they came right out. Boy, was I pissed! All the effort that I put trying to take 'em out myself must have helped him out! (---at least, that's what I tell myself :P ) It may have been easier also because the car was up on a lift --better leverage.

Anyway, I hope it works out for you!! Post some pics and let us know what happens!

-Dana

Edited January 20, 2008 by dcporsche99

[Stefan]

Dana,

Just to clarify: you're talking about the studs, not the nuts, right? I am trying to remove the studs.

[dcporsche99]

Yes, Stefan...I am referring to the studs. My Porsche mechanic placed the large vise grip perpendicular to the stud after he heated it up....mind you, this gentleman is a very big fellow (over 250 lbs)....so, one after the other (heat, clamp, twist w/ brute force, and off each one of them came)....it blew me away at how easy he made it seem.

Anyway, how did it go for you? Did you heat and sledgehammer away each of the studs? (j/k) :)

Edited January 20, 2008 by dcporsche99

[pomocanthus]

This is a little odd. When you heat metals they will expand, so the bolts would seem to expand and be even tighter in the holes of the flange. If you heat the flange instead, I think it would expand the hole and allow you to remove the bolt more easily. Perhaps Dana's mechanic heated the bolts so they expand and break any corrosive bonds to the flange. Eventhough the bolts expanded and was a little tighter in the holes, the BIG gentleman just muscled them out. Does this make sense? I'm about to replace my headers and was reading up on all suggestions. What values did you guys torque the bolts to the block to? What about the bolt and nut connecting the headers to the cats?

Stefan, it seems that I am doing a lot of the same R&R you've done (just a few months behind).

Thanks,

Hung

[Stefan]

The torque fo the exhaust manifold to cylinder head is 25 nm (19 ft. lb.).

The last nut connecting the header to the cats is really hard to get at so I haven't done that yet. The rest I was able to remove essentially by weakening the nuts by cutting into them with a dremel, heating them up with a torch, and twisting with vice grips.

I haven't removed any of the studs from the cats.

[pomocanthus]

Stefan,

I was able to replace the passenger side header today (in between watching Aussie Open). I was fortunate in that a couple of years ago factory replaced the passenger side cat and they used regular bolts to replace the pressed fit ones. With a little overnight soaking of PB Blaster, they came right out. I haven't tried the driver side yet since it still has the original pressed fit bolts. I'm leaving that challenge for tomorrow. I have an idea on how to press out those bolts and will let you know how it worked out.

Hung

[Stefan]

I got the last header to cat nut off today but the header seems to be fused to the cat nevertheless. I am going to drive around that way and hopefully the heat and vibration will loosen them from each other.

[dcporsche99]

I got the last header to cat nut off today but the header seems to be fused to the cat nevertheless. I am going to drive around that way and hopefully the heat and vibration will loosen them from each other.

Hey Stefan,

Just read your response to my earlier PM, but didn't have a chance to respond back until now. Nice job on getting that last nut off!! BTW, if the drive doesn't loosen it, you could probably just take a rubber mallet to where they meet while supporting the header / manifold end so it doesn't fall on top of you. You're almost done!

Hi Hung,

Perhaps it does not make a whole lot of sense, ....though I have not analyzed it to quite the extent that you have.... it worked nevertheless. Good luck on your future install.

BTW, w/c angelfish (pomocanthus) do you like best?? Take care.

-Dana

Edited January 20, 2008 by dcporsche99

[pomocanthus]

Dana, Stefan

One of the threads talked about tie-wrapping an AC line away from the headers and wrapping with insulating wrap. Did you wrap? I searched web and found that people wrap the headers to keep everything else cool and to keep the exhaust gases hot. The idea is that hot gases is less dense than cooler gases and thus can travel faster towards the cats and muffler and ultimately out. It sounds plausible but will it cause any problems with the cats? Will hotter gases going into the cats cause problems or do the cats generate much higher heat and won't be affected?

Thanks,

Hung

p.s. fav in my tank is French Angel

Edited January 20, 2008 by pomocanthus

[dcporsche99]

Dana, Stefan

One of the threads talked about tie-wrapping an AC line away from the headers and wrapping with insulating wrap. Did you wrap? I searched web and found that people wrap the headers to keep everything else cool and to keep the exhaust gases hot. The idea is that hot gases is less dense than cooler gases and thus can travel faster towards the cats and muffler and ultimately out. It sounds plausible but will it cause any problems with the cats? Will hotter gases going into the cats cause problems or do the cats generate much higher heat and won't be affected?

Thanks,

Hung

p.s. fav in my tank is French Angel

Hi Hung,

Yes, I did. I used header wrap around the AC line and used zip ties to keep the AC line (located on the driver's side) as far from the header as possible. From my understanding, it simply keeps the AC line from getting hot. Therefore, the AC does not have to work twice as hard.

Also, there were a few instances where I actually had to wrap parts of the header (located on the passenger's side)--at the collector by the flange and, if my memory serves me correctly, along one or two other areas. These were done solely for the purpose of dampening some of the vibration / resonance that I was experiencing.

... all interesting questions...perhaps best answered by the more knowledgeable folks out there....Loren?? Stefan?? :)

-Dana

Edited January 20, 2008 by dcporsche99

[Stefan]

I hadn't wrapped the A/C line because I guess I didn't read that thread. It makes perfect sense and I will look into it.

As to the header wrap, that is also a well founded idea. Getting the heat away from the engine (and the engine compartment) efficiently is important and heat wrap definitely helps. Whether or not it makes a perceptible difference I do not know.

I tried hammering a screwdriver between the header and the cat and it wouldn't go in. I didn't want to hit it too hard because I was worried about the O2 sensor. I will get it apart, one way or another. I'm just happy to have gotten that ridiculously welded nut off. I really had to destroy it before it would budge.

[dcporsche99]

I hadn't wrapped the A/C line because I guess I didn't read that thread. It makes perfect sense and I will look into it.

As to the header wrap, that is also a well founded idea. Getting the heat away from the engine (and the engine compartment) efficiently is important and heat wrap definitely helps. Whether or not it makes a perceptible difference I do not know.

I tried hammering a screwdriver between the header and the cat and it wouldn't go in. I didn't want to hit it too hard because I was worried about the O2 sensor. I will get it apart, one way or another. I'm just happy to have gotten that ridiculously welded nut off. I really had to destroy it before it would budge.

Stefan,

....at least you knew it was welded on. I didn't realize it until I was working on it for quite some time. It's like trying to open a childproof bottle without knowing it was childproof. :P

As for the 02 sensor, I have not seen data to support that, although it makes perfect sense. But, one way or another you are bound to introduce some kind of vibration / shock, if you haven't already, when you give the header a good shake to get it off. Perhaps, as suggested before, the only way to get around that would be to remove the sensor, tie it off and get it out of the way.

BTW Hung, as far as I know, you may very well be correct in your thinking about premature cat failure secondary to increased heat from completely wrapping the header(s)...but, you should definitely look for supporting data on that. As I said before, ...all interesting questions....how's your install going? Did you decide to tackle the driver's side yet??

Edited January 20, 2008 by dcporsche99

[pomocanthus]

Finally got the driver side finished. Now I know what all the fuss was about. The pressed in bolts were a pain to remove but thanks to Dana's and Stefan's suggestions of heating with propane and using a B.A.H. it only took about 1 hour to remove. At least I don't have to go do weights at the gym today; after swinging that B.A.H. at the bolts. It has gotten cold and dark so I haven't put the underbody panel back on yet. Needless to say I haven't driven her around although I did fire her up. The sound is different but I can't quite pinpoint what the difference is. Perhaps tomorrow when I'm driving her around, celebrating MLK Day.

One thing of note: the bolt holes on the cat side fits the bolt just right while on the after-market header side it is oblong, allowing for minor location adjustments. Because of this I think it is better to feed the bolt through the cat-side flange towards the headers. This way the neck of the bolt (unthreaded) fits almost perfectly inside the holes on the cat-side flange. Besides, this is the only way I could do it for the top bolt because of interference from the VarioCam housing. I also noticed that the top bolt sticks out too far through the header flange and comes awfully close to that VarioCam housing. I imagine that vibration from engine and road may cause the assembly to move enough so that the bolt could rub against the VariaCam housing. To "shorten" the bolt, I simply added washers on the cat-side; at the head of the bolt. This way more of the bolt is on the cat-side and less sticks out on the header side. You have to play with the number of washers to get enough of the bolt away from the VarioCam housing and still have enough threads for the nut. I'll take some pics and post tomorrow.

Hung

Edited January 21, 2008 by pomocanthus

[dcporsche99]

Finally got the driver side finished. Now I know what all the fuss was about. The pressed in bolts were a pain to remove but thanks to Dana's and Stefan's suggestions of heating with propane and using a B.A.H. it only took about 1 hour to remove. At least I don't have to go do weights at the gym today; after swinging that B.A.H. at the bolts. It has gotten cold and dark so I haven't put the underbody panel back on yet. Needless to say I haven't driven her around although I did fire her up. The sound is different but I can't quite pinpoint what the difference is. Perhaps tomorrow when I'm driving her around, celebrating MLK Day.

One thing of note: the bolt holes on the cat side fits the bolt just right while on the after-market header side it is oblong, allowing for minor location adjustments. Because of this I think it is better to feed the bolt through the cat-side flange towards the headers. This way the neck of the bolt (unthreaded) fits almost perfectly inside the holes on the cat-side flange. Besides, this is the only way I could do it for the top bolt because of interference from the VarioCam housing. I also noticed that the top bolt sticks out too far through the header flange and comes awfully close to that VarioCam housing. I imagine that vibration from engine and road may cause the assembly to move enough so that the bolt could rub against the VariaCam housing. To "shorten" the bolt, I simply added washers on the cat-side; at the head of the bolt. This way more of the bolt is on the cat-side and less sticks out on the header side. You have to play with the number of washers to get enough of the bolt away from the VarioCam housing and still have enough threads for the nut. I'll take some pics and post tomorrow.

Hung

Nice job Hung! How's your ride now?? Hope you're enjoying your mod! :P

Interesting way of solving that issue.,,,,but, why not just shorten the bolt with a dremel? BTW, now that I think about it, how did you manage to fit a long bolt (for the top of the passenger's side flange) from the cat side to the header without the housing getting in the way?? From my recollection, there's not much room to fit much of anything. If you added washers on the cat side, surely there wouldn't be room to get washers and a bolt in there at such a tight angle.... :o WOW, I'm amazed! Do you have a picture?? I'm just curious as to what it looks like. I've added a crappy picture of the area I'm talking about ---it's encircled in yellow....maybe we're talking about different things entirely... :)

Edited January 21, 2008 by Loren
made image viewable

[dcporsche99]

Finally got the driver side finished. Now I know what all the fuss was about. The pressed in bolts were a pain to remove but thanks to Dana's and Stefan's suggestions of heating with propane and using a B.A.H. it only took about 1 hour to remove. At least I don't have to go do weights at the gym today; after swinging that B.A.H. at the bolts. It has gotten cold and dark so I haven't put the underbody panel back on yet. Needless to say I haven't driven her around although I did fire her up. The sound is different but I can't quite pinpoint what the difference is. Perhaps tomorrow when I'm driving her around, celebrating MLK Day.

One thing of note: the bolt holes on the cat side fits the bolt just right while on the after-market header side it is oblong, allowing for minor location adjustments. Because of this I think it is better to feed the bolt through the cat-side flange towards the headers. This way the neck of the bolt (unthreaded) fits almost perfectly inside the holes on the cat-side flange. Besides, this is the only way I could do it for the top bolt because of interference from the VarioCam housing. I also noticed that the top bolt sticks out too far through the header flange and comes awfully close to that VarioCam housing. I imagine that vibration from engine and road may cause the assembly to move enough so that the bolt could rub against the VariaCam housing. To "shorten" the bolt, I simply added washers on the cat-side; at the head of the bolt. This way more of the bolt is on the cat-side and less sticks out on the header side. You have to play with the number of washers to get enough of the bolt away from the VarioCam housing and still have enough threads for the nut. I'll take some pics and post tomorrow.

Hung

Nice job Hung! How's your ride now?? Hope you're enjoying your mod! :P

Interesting way of solving that issue.,,,,but, why not just shorten the bolt with a dremel? BTW, now that I think about it, how did you manage to fit a long bolt (for the top of the passenger's side flange) from the cat side to the header without the housing getting in the way?? From my recollection, there's not much room to fit much of anything. If you added washers on the cat side, surely there wouldn't be room to get washers and a bolt in there at such a tight angle.... :o WOW, I'm amazed! Do you have a picture?? I'm just curious as to what it looks like. I've added a crappy picture of the area I'm talking about ---it's encircled in yellow....maybe we're talking about different things entirely... :)

Hi,

...BTW, I was getting quite a few number of folks asking me for this DIY header install PDF. I didn't know where else to post it, so Loren feel free to move it around as you see fit.

I also posted this on 986forum.

Hope this helps others! :thumbup:

diy_for_header_install.pdf

[pomocanthus]

Nice write up Dana! Sorry for slow response. Here's a pic of the top bolt on the passenger side that I was talking about. Note the three washers on the cat side. Also note (not related to the pic), make sure you tighten the nut on the bung of the header. The after-market header that I bought was made for either the Boxster or Boxster-S, so it had a bung for installing O2 sensor (for Boxster-S). I figured it was tight from factory so I didn't bother; well it rattled OFF during my morning commute. I didn't have an extra plug so I was in a bind. No local source had it and overnight delivery from Pelican was going to be $50. Since it was made for an O2 sensor, I simply installed an old O2 sensor I had from previous R&R. It sealed fine and I am driving her around until the plug comes.

The R&R was definitely worth it. The car sounds soooo much better. The exhaust no longer sounds like an indistinguishable loud vacuum cleaner but has more tone to it. The car also accelerates better. The slight hesitation in 2nd gear is now completely gone. This will keep me happy for at least 2 weeks :D