ahardb0dy Posted December 18, 2011 Share Posted December 18, 2011 Hello, been working on the exhaust on my 90 sentra for a few weeks now, pulled the cat to check it out, it was clogged so I gutted it and put it back on, MPG came up about 4 MPG, all good so far but the noise from the exhaust hitting that empty cavity and sounding like there was an exhaust leak was driving me crazy. So I decide to pull the cat completely and make a spacer so I can join the flanges together, didn't want to cut the flanges out so I could put a new cat on later on. I found a piece of 3/4" thick steel at work and started to machine it to match an exhaust gasket. I was only using a drill, jigsaw and hacksaw and it took my a few weeks to get the steel to be the same shape as the gasket, used a carbide bit in my die grinder to do the finally shaping and smoothing, it came out pretty good. I get under the car, remove the hollowed out cat, cut the pipe behind the rear flange, put my new spacer in, using the Nissan gaskets I bought a few weeks earlier, bolt it all up, extend the rear pipe to connect to where I cut the flange out, started the car, exhaust leak from near my spacer !!, bought 2 new fel-pro flange gaskets, swapped them in for the stock one's, started it up, still leaking!!, took it apart, put a fel-pro gasket and a stock metal gasket on each side, still leaking !! took it apart, 2 fel-pro gaskets on the rear flange stock metal gasket on the front, started it up, front is sealed good rear flange still leaking !! UGGGGG!!! Took the rear flange out of the pipe along with the spacer into my shed, checked the spacer with straight edge it was flat, layed the flange on it and it is bowed, tried to flatten it but still wouldn't seal. Was going to but the pipe after the cat and cut what I needed out of it just to get a new flange but none of the local auto parts stores had it, decided to take the flange and one gasket to auto parts store to try and match the flange up with one on another pipe from another car, but auto parts store does not stock pipes for ANY car!! Now on to plan "B", decided to cut the front flange off and just pipe the 2 ends together, bought another section of pipe, got home got the pipe in, started the car, no leaks !! FINALLY. So I drive the car to work next 4 days and it keeps getting louder and louder, checked under the car and now have a leak where one of the pipes slips into the other!! Got under the car yesterday and couldn't get the pipe to go in any further so called an exhaust shop to see what they would charge me to make me a 30" pipe with expanded ends guy says $16 so I say I'll be there in 20 minutes. Get to the muffler shop, wait 45 minutes than the owner calls me into the back, seems he thought he had a 7' length of 1.75" pipe but now realizes he only has an 18" piece, so he asks me if I mind if they cut the pipe in the middle and says they will weld in a section of 2" to get to my total length of 30", I said that's fine if they would do it for the same price, he said they would. They make the pipe and I head home. I remove my mess of pipes and couplers and get the new pipe in, put one normal u-bolt clamp on each end, tighten them down, start the car, have a small leak on each end !!!, played around with the clamp position and got the front end to stop leaking, rear still leaking. So, (sorry so long), any special way to tighten these clamps to get it to seal? should I tighten them using the impact gun? I was using a 3/8" ratchet. Was looking at different style of clamps but not many options available under a 2" pipe. The muffler shop told me if I can't get it to seal I could bring it in and they could weld the pipes, may call the shop tomorrow to see if they will do that and what they will charge me. I know it's against the law to remove the cat converter and I do plan on putting one back on in the future so no lectures please, thanks Link to comment Share on other sites More sharing options...
Precise1 Posted December 18, 2011 Share Posted December 18, 2011 So I decide to pull the cat completely B Link to comment Share on other sites More sharing options...
ahardb0dy Posted December 18, 2011 Author Share Posted December 18, 2011 I know, it's only temporary Link to comment Share on other sites More sharing options...
silverton Posted December 18, 2011 Share Posted December 18, 2011 I've only ever used a box wrench to tighten these U-bolt exhaust clamps. If you put too much pressure on it, it'll just crimp the pipe and cause a leak. I have one of these holding the muffler on my 200sx, and it has a slight leak. Can't hear it over the car, but you can see the black mark from the carbon. I'm going to guess it's just the nature of the beast. Link to comment Share on other sites More sharing options...
Tungsten Posted December 18, 2011 Share Posted December 18, 2011 meh use a test pipe i doubt florida would care about crapalytic converters Link to comment Share on other sites More sharing options...
Precise1 Posted December 19, 2011 Share Posted December 19, 2011 I know, it's only temporary Ok, just a pet peeve of mine. I'm having a hard time seeing your connection/leak in my head, can you post a picture? In my experience, over tightening exhaust components usually causes problems instead of curing them so no, leave the impact gun alone. I prefer using band clamps, what diameter are you talking about? I'm not sure if it would help in this application, but I've had good luck with Permatex Copper sealant for exhaust seals. B Link to comment Share on other sites More sharing options...
nunya Posted December 19, 2011 Share Posted December 19, 2011 band clamps are the way to go (other than welding it up good and snug, but you want to take it apart again when you get the right stuff) Link to comment Share on other sites More sharing options...
ahardb0dy Posted December 19, 2011 Author Share Posted December 19, 2011 Pipe is 1.75", connection is one pipe slipped into the other. Link to comment Share on other sites More sharing options...
sewebster Posted December 19, 2011 Share Posted December 19, 2011 Those u-bolt things always leak for me too. Link to comment Share on other sites More sharing options...
Precise1 Posted December 19, 2011 Share Posted December 19, 2011 Pipe is 1.75", connection is one pipe slipped into the other. Yeah, I couldn't find much for that size but IIRC most stock Harley exhaust is 1.75" so a slip fit band clamp might be found with them, or at least a source... B Link to comment Share on other sites More sharing options...
JamesRich Posted December 19, 2011 Share Posted December 19, 2011 Yeah, I couldn't find much for that size but IIRC most stock Harley exhaust is 1.75" so a slip fit band clamp might be found with them, or at least a source... B With what he will pay for a harley part he could buy a new converter, or is that your idea? Get the shop to weld it and that should fix your problem. From what I'm understanding you are using the flanges from your old cat to make a test pipe, so you can still bolt a new cat up later? James Link to comment Share on other sites More sharing options...
ahardb0dy Posted December 19, 2011 Author Share Posted December 19, 2011 (edited) No flanges anymore, original idea was to pull the cat, cut the pipe after the rear flange, move it forward to the front flange and using the spacer I made bolt the 2 flanges together, than add a piece of pipe from where I cut the pipe after the rear flange and tie it into the pipe that I cut (after the rear flange), the spacer I made came out good but the rear flange was warped and would not seal, so I ended up cutting the front flange off, removing the rear flange, and connecting the 2 halves of pipe. Going to call the muffler shop in a few to see if they will weld the 2 ends of the pipe for me. After x-mas will pick up a universal cat, was looking at a Magnaflow for about $67 Edited December 19, 2011 by ahardb0dy Link to comment Share on other sites More sharing options...
Tungsten Posted December 20, 2011 Share Posted December 20, 2011 (edited) I would just give the muffler shop the whole deal with the cat and have them work it out. If you really need a cat for whatever reason, those Magnaflow universal cats are really good, you can definitely go with one of those. I had one for a while before I switched to a bigger diameter pipe. Edited December 20, 2011 by Tungsten Link to comment Share on other sites More sharing options...
JamesRich Posted December 20, 2011 Share Posted December 20, 2011 I'd just go with the new cat and be finished with it. The muffler shop will probably charge you half that just to weld your current setup. James Link to comment Share on other sites More sharing options...
nismothunder Posted December 21, 2011 Share Posted December 21, 2011 Goodness your posts are always long. I crank the bastards until it crush's the two pipes togeather. I have always done that and have never had a leak. But welding is really best. Link to comment Share on other sites More sharing options...
ahardb0dy Posted December 26, 2011 Author Share Posted December 26, 2011 Called muffler shop on Friday, they told me $30 to weld the pipe, took it in and the guy changes his mind, said he could sell me the pipe because he doesn't know what I'm going to do with it but can't work on the car with no cat on it. He said he would tighten the clamps as a x-mas gift to me if I wanted, so he put it on the lift, both ends had small leak, than he hands me the impact gun, so I figured he doesn't want to touch the car at all, no problem, I tightened the hell out of the 2 clamps and it still leaks a little bit, he suggested using some of the muffler putty in the gaps. I asked if they would install a cat if I provided it and he said he would $85 to install it and weld the 2 pipe ends ( would be legal than), I told him in a few weeks I may be back. Link to comment Share on other sites More sharing options...
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