rusted exhaust bolt removal?

[Jimmy9190]

I have to replace one of the catalytic convertors on my truck. I have the California Emissions system with 2 mini-cats up front and a larger main cat in front of the muffler. Rather than pay a shop $800.00 to replace just the one defective cat I am planning to buy the entire assembly with the 2 mini-cats, pipes and main cat convertor and replace it all and be done with it. I figure if one mini-cat is bad the other is probably not far behind. I can get the assembly from Rock for about $380.00 shipped. I have 2 cats up on either side of the transmission just below the exhaust manifolds.

The cats have short pipes going up to the donut junction from the manifold. Each one has 2 bolts on it, they are rusted and probably seized tight from thousands of heat and cool down cycles. Question is how do you remove the nuts? Is it possible to get the nuts loose without breaking the bolts off? Or should I count on the bolts breaking off and having to drill the bolts out? I am thinking it will be best to spray with Kroil or PB Blaster the night before I start the job. Am I right in assuming the bolts have to be replaced with new ones? Any help here is much appreciated.

 

[Kruse]

This is a job best left to an acetylene torch, a torch that can create lots of heat.

 

[simple_gifts]

I would not hang $380 from anything old.

The overnight soak is a good idea, plus and mild warm up prior to trying to do the work.

 

[DragRace]

Torch,drill,hacksaw,and a hammer are usually the tools needed in removing an old,rusty exhaust system.

I ALWAYS use new bolts,hardware when replacing with new,as it's not a fun job,period.The last thing I want to do,is get back underneath the vehicle and do it all over again.

 

[SuperDave456]

I've had good results with rusted bolts on a mast antenna before, but I brought a hack saw with me just in case.

Never done much exhaust work, but from what I have experienced look for a Mapp or Acetylene torch. I think they sell Mapp/Oxygen torches at the local Home Depot.
If the overnight soak doesn't work, I would make a run to the store and bring the heat.

 

[JC1]

Originally Posted By: Jimmy9190
I have to replace one of the catalytic convertors on my truck. I have the California Emissions system with 2 mini-cats up front and a larger main cat in front of the muffler. Rather than pay a shop $800.00 to replace just the one defective cat I am planning to buy the entire assembly with the 2 mini-cats, pipes and main cat convertor and replace it all and be done with it. I figure if one mini-cat is bad the other is probably not far behind. I can get the assembly from Rock for about $380.00 shipped. I have 2 cats up on either side of the transmission just below the exhaust manifolds.

The cats have short pipes going up to the donut junction from the manifold. Each one has 2 bolts on it, they are rusted and probably seized tight from thousands of heat and cool down cycles. Question is how do you remove the nuts? Is it possible to get the nuts loose without breaking the bolts off? Or should I count on the bolts breaking off and having to drill the bolts out? I am thinking it will be best to spray with Kroil or PB Blaster the night before I start the job. Am I right in assuming the bolts have to be replaced with new ones? Any help here is much appreciated.


Jimmy,

You can try the heat, but you might need a hacksaw, or sawzall to get the bolts off. Sometimes the bolts start to crumble when you touch them with force. Good luck.

Regards, JC.

 

[nitehawk55]

Good ol blue flame wrench

 

[KB2008X]

For me whenever I tackle a job like that, the key is being careful to not round off the bolt heads or nuts. Once that happens you've made a tough job even harder. So choose your tools and technique wisely.

What you'll need to do is determined by whether it's nuts on studs, bolts into a boss or bolts into nuts. If it's bolts into nuts and the bolt is free from the boss, snapping the bolts can be a good thing. If it's nuts on studs or bolts into bosses more care will be needed. Find out for sure what you're actually up against before you start, it makes a difference.

For sure soaking with PB Blaster or something similar will help, and heat will be your friend if you let it. A Sawzall can be very helpful, too.

 

[The_Eric]

Torch. I've removed some of the worst looking fasteners like they weren't even tight after a blast from the torch. Don't be bashful either. Hit em hard. Get them at least orange if not yellow.

 

[eljefino]

Those usually come right off. They anti sieze them right up at the factory. Is this one of the junctions with the valve spring looking things holding two flanges around the donut? Plenty of good ways to rig that up if you snap anything, and it's not the end of the world to drill out either.

As said above the most important thing is not rounding off the heads. If it's a 13mm, hammer a 1/2" on.

 

[Jimmy9190]

Thanks for the replies. I don't believe these have springs. I can feel the top of the bolts and I think it is bolt going thru the holes in each flange, but it does not have a hex head on the top side, it is just a flat end of the bolt itself. It feels like it is shaped like a rectangle. I am thinking maybe there is not enough room up on that side of the flange for a hex head. I think if the bottom stud end snapped off I could push the bolt back out thru the hole. I don't know about the anti-sieze, I have no way to tell if it was used at the factory.

I do believe I can do this job though. I put my truck up on ramps and got under it with a print-out of the cat/pipe assembly from the Rock Auto web site to be sure I am buying the right part. I studied it a long time. Rock is the only place I could find a replacement California Emissions setup for a 2 wheel drive Dakota. If I had 4WD it's $100.00 cheaper on Ebay. I think it is a much better idea to replace the entire assembly now than to just do the one bad cat. I don't want to do this job again so I may even replace the muffler while I am at it. The only thing bugging me about it is the rusted exhaust flange bolts.

I am thinking it might be easier and less work to just take a Sawzall and cut the pipes just below the donuts, then get the old assembly out from under the truck. That would give me much better access to the nuts, but only one looked like it would be hard to get to. I will order the assembly next week and probably do the job over the weekend of the 9th thru 11th. Veterans' Day is on a Monday this year and will be a holiday for me. I know I will probably need the extra time..

Thanks again guys.

 

[yonyon]

It sounds like you have a pretty good grasp of what you're in for and what options you have. The best advice I can give you is this:

If what you're doing looks like it isn't working out as well as you hoped, take a break and go do something else. By the time you're done with the other thing you'll have a better idea.

 

[KB2008X]

Doing exhaust work while laying on your back can be tough, it's much easier on a lift, so be sure to get the vehicle as high up as you safely can. Also, I would strongly advise you to not cut the pipes off. It's not necessary and if you reach a point where it seems like a good idea, you're doing something wrong. You'd be surprised how many times replacement exhaust pipes aren't bent right, or the length isn't quite right, or they get bent in shipment, or they just flat out sent the wrong thing, and if you've cut the old ones off you'll be sorry.

The hot and cold cycles that you mentioned in your original post are actually a good thing. The heat chases moisture out from the threads and helps preserve them, but the heads of the bolts will be eroded, partially from those same heat cycles. Head pipes generally come apart pretty good, assuming the heads of bolts aren't already messed up and you don't round them off and make them worse.

Having a good selection of 1/2" drive sockets and extensions, and a good heavy duty swivel help a lot.

Plan ahead for dealing with chunks of rust in the eyes.

You're saving some serious jack doing this job yourself, just don't forget to spend a little bit of that savings on gear to get it done right.

 

[Jimmy9190]

Thanks for the tips. I think I can get at that one hard to reach flange nut either with a u-joint and long extension or by removing the wheel on that side. There is a big enough hole in the fender liner that would let me swing a wrench or use a Gear Wrench on it once I get the nut loosened up. If that fails I can always remove the fender liner and heat shield to get better access to that one nut.

I will give all of the bolts and nuts a good dose of Kroil the night before and again the morning I start the job. I inherited a couple cans of Kroil from my father in law. It's good stuff. I have at least one if not two cans of PB Blaster too. The one thing I don't have is a good set of metric deep well 1/2" drive sockets. I may swing by HF one night next week for those and some wobble drive extensions. Other than that I think I have all the tools I will need.

I plan on doing this job in my driveway as long as it is not raining. The driveway slopes slightly down and then slightly up again leading into the garage. I found the sloped area combined with my ramps lifts the front and middle sections of my truck up off the ground higher than ramps on a level surface. I figure that will help with better access to the exhaust. I also checked out pics of new exhaust manifolds on the Rock Auto site, and the end of the manifold where it bolts to the flange for the pipe leading to the cat, that end has holes in it for a bolt to pass through. That leads me to believe if one of my original bolts breaks off then maybe I can drill or push it out without too much hassle.

 

[wtd]

After the last few failed attempts on working on rusted exhaust bolts and O2 sensors, I just take it to an exhaust shop and let them do it. The aggrevation is just not worth it to me anymore.

Heat is your friend. Just make sure whatever you have will get the metal hot enough. Good luck.

Wayne

 

[Rick in PA]

Originally Posted By: The_Eric
Torch. I've removed some of the worst looking fasteners like they weren't even tight after a blast from the torch. Don't be bashful either. Hit em hard. Get them at least orange if not yellow.


^This^ (see my signature) Just remember that nut will be good 'n hot for a long time. Do not step on it, or for heaven's sake, pick it up.

 

[1 FMF]

not familiar with your vehicle but i had to repair broken studs on my truck holding the exhaust manifold to cylinder head, and i had to remove the catalytic converter down pipe from the exhaust manifold. you are most likely wasting your time & money using any penetrating oil. you will need an acetylene torch to heat the studs and nuts cherry red to remove them. if you can remove the front wheel well covers (along with the front wheels) you may have very easy access to the exhaust manifolds and down pipe. just be aware that once you start heating it you are going to harden the metal so if anything breaks it'll be that much harder to drill out. and if you have the access, one you've heated things up one trick is to use a candle and melt wax on the threads to help remove them. you can see vids about that on youtube, however if you've got the entire fastener cherry then you don't need wax. the wax is helpful for something like a stud going into the manifold flange where you aren't heating the entire flange cherry red. good luck.

 

[zzyzzx]

I would cut off the old bolts with an angle grinder. It's not like you can really reuse old, rusted exhaust bolts.

 

[JamesBond]

What is wrong with the catalytic converter? Why do you need to replace it? if its just a check engine light, you could get away with just changing the sensor or something.

I like to spray with PB blaster or something then put on a couple drops of motor oil, then repeat often for as long as you have. If you are still driving the car, whatever you spray on will kind of burn up/burn off so its best if you can let the car sit for a day or two.

 

[Jimmy9190]

Thanks for all the replies and tips here. I have not yet ordered the cat assembly form Rock. I am still reading and researching my P0432 code. It may be that the cat is OK and I have an exhaust leak, vacuum problem or possibly the upstream O2 causing the problem. The upstream O2 only has about 60,000 miles on it, it is an NTK sensor and I do not see how it could be bad this soon but I guess anything is possible.

I am going over to HF tonight after work and pick up an infrared thermometer gun to check the inlet and outlet temps on the cat. I want to check that and do a vacuum check before buying a $380.00 part. My truck runs fins, there is no loss of power, rotten egg smell or other physical signs of a bad cat. I hit all cats with a rubber hammer last week, no noise or rattles from amy of them. I appreciate the help if anyone has any ideas about this problem.