Help!! Exhaust Leak

1991GT · 12-13-2002, 01:46 AM

After 2 weeks, a returned set of headers and tailpipes that didnt fit, I finally got my exhaust on my car (BBK 1 5/8 ceramic unequal shorties, BBK h-pipe w/ cats, and flowmaster 2 chambers). Well its sounds sick as hell BUT I have a wonderful exhaust leak that I don't know what to do about. I'm almost positive its coming from the right side header where it bolts up to the h-pipe. the alignment didnt look too swift when I was installing it but i thought the flange would straighten itself out as I tightened it. Also the car feels much slower and feels like I lost power all throughout the rpm range, which I could understand some torque loss because everything is bigger diameter than stock, but not like this. Maybe the leak is causing the power loss?? Also sounds like its misfiring too but I think that may just be the leak that I'm hearing. I did trim the header flange with a carbide cutter to 2 1/2in diameter because it came from the factory at only 2 1/4in and I wanted everything to match. I put black silicone around the flange to try and make it seal better in case I got a leak like this. I also disconnected the battery for a day or so to clear the computer. I only drove it for 8 miles so maybe the computer hasn't re-learned everything yet. I really don't know what else to do...tomorrow I'm going to try and unbolt the header flange and re-align it and hopefully that will fix the problem. Please give me some ideas, I'm desperate!! The leak just makes an otherwise beautiful sounding exhaust sound like crap and the car doesnt feel fast anymore. Help!!

Bad89stang · 12-13-2002, 01:57 AM

Just re-do the connections to the H-pipe. Undo both of them and make sure that they line up correctly. Then tighten them down a little at a time. Switch sides back and forth until you are sure they are tight. For insurance you can add 3-4 washers on each side to get them to tighten earlier. I have screwed with this problem on a friend's car more than I would like to admit.

1991GT · 12-13-2002, 11:37 AM

I went outside this morning and tried tightening up the flange more. Didn't help. I didn't have the time to unbolt both and re-align them (I did this whole project on my back using jackstands, wish I knew someone that had a lift

) I also checked the plug wires to make sure they were fully seated incase I was hearing a misfire. Two other things I noticed, 1) The exhaust does smell rather rich but maybe its due to the new O2 sensors and exhaust and 2) It did not start leaking until it warmed up. Tonight I will try unbolting and re-aligning the h-pipe/header flanges. Hope that fixes it otherwise I'm going to have to take it somewhere and spend $ that I don't have

bigred90gt · 12-13-2002, 12:44 PM

I had the same problem with my Bassani o/r X pipe. I had to cut the pipe, on the side that had the leak, bolt the piece to the header, and then weld a sleeve to cover the gap. Looks bad but works. I don't know if you will have room to do so with the cats, but It's worth a look.
Caymon

RED92LX50 · 12-13-2002, 01:23 PM

If you are sure the leak is at the header/h-pipe junction, you may be able to put a bead of muffler mender around the joint to stop the leak. It is smilar to using plumbers putty on leaky pipe joints. I used it on one of my connections and have not had any problems in over 6 years.

Otherwise, maybe the leak is at the heads - in which case you can retorque those bolts (as they can loosen a little after the inital install with the first few heat cycles).

1991GT · 12-13-2002, 09:39 PM

Thanks for all the help. I can't work on it tonight because it's raining but I should be able to work on it over the weekend. I'll keep you guys posted.

12-13-2002, 01:46 AM	#1
1991GT Registered Member Join Date: Jul 2002 Location: Flemington, NJ Posts: 13	Help!! Exhaust Leak After 2 weeks, a returned set of headers and tailpipes that didnt fit, I finally got my exhaust on my car (BBK 1 5/8 ceramic unequal shorties, BBK h-pipe w/ cats, and flowmaster 2 chambers). Well its sounds sick as hell BUT I have a wonderful exhaust leak that I don't know what to do about. I'm almost positive its coming from the right side header where it bolts up to the h-pipe. the alignment didnt look too swift when I was installing it but i thought the flange would straighten itself out as I tightened it. Also the car feels much slower and feels like I lost power all throughout the rpm range, which I could understand some torque loss because everything is bigger diameter than stock, but not like this. Maybe the leak is causing the power loss?? Also sounds like its misfiring too but I think that may just be the leak that I'm hearing. I did trim the header flange with a carbide cutter to 2 1/2in diameter because it came from the factory at only 2 1/4in and I wanted everything to match. I put black silicone around the flange to try and make it seal better in case I got a leak like this. I also disconnected the battery for a day or so to clear the computer. I only drove it for 8 miles so maybe the computer hasn't re-learned everything yet. I really don't know what else to do...tomorrow I'm going to try and unbolt the header flange and re-align it and hopefully that will fix the problem. Please give me some ideas, I'm desperate!! The leak just makes an otherwise beautiful sounding exhaust sound like crap and the car doesnt feel fast anymore. Help!! __________________ '91 GT - 135K miles T-5, stock 2.73's uugh, MAC cold air, Pro-M Bullet 75mm, BBK 1 5/8 jet-hot unequal shorties, BBK h-pipe w/ cats, Flowmaster 2 chambers, Pro 5.0 short throw, KYB shocks and struts In the garage waiting to be put on: Screamin Demon coil, Dyna Mod TFI module, underdrive pulleys

12-13-2002, 01:57 AM	#2
Bad89stang Registered Member Join Date: Aug 2001 Location: Ft. Worth, TX Posts: 456	Get back under there... Just re-do the connections to the H-pipe. Undo both of them and make sure that they line up correctly. Then tighten them down a little at a time. Switch sides back and forth until you are sure they are tight. For insurance you can add 3-4 washers on each side to get them to tighten earlier. I have screwed with this problem on a friend's car more than I would like to admit. __________________ You're gonna need your seatbelt

12-13-2002, 11:37 AM	#3
1991GT Registered Member Join Date: Jul 2002 Location: Flemington, NJ Posts: 13	I went outside this morning and tried tightening up the flange more. Didn't help. I didn't have the time to unbolt both and re-align them (I did this whole project on my back using jackstands, wish I knew someone that had a lift ) I also checked the plug wires to make sure they were fully seated incase I was hearing a misfire. Two other things I noticed, 1) The exhaust does smell rather rich but maybe its due to the new O2 sensors and exhaust and 2) It did not start leaking until it warmed up. Tonight I will try unbolting and re-aligning the h-pipe/header flanges. Hope that fixes it otherwise I'm going to have to take it somewhere and spend $ that I don't have __________________ '91 GT - 135K miles T-5, stock 2.73's uugh, MAC cold air, Pro-M Bullet 75mm, BBK 1 5/8 jet-hot unequal shorties, BBK h-pipe w/ cats, Flowmaster 2 chambers, Pro 5.0 short throw, KYB shocks and struts In the garage waiting to be put on: Screamin Demon coil, Dyna Mod TFI module, underdrive pulleys

12-13-2002, 12:44 PM	#4
bigred90gt 2 Stangs in the Stable Join Date: Apr 2002 Location: Baytown, TX Posts: 1,209	I had the same problem with my Bassani o/r X pipe. I had to cut the pipe, on the side that had the leak, bolt the piece to the header, and then weld a sleeve to cover the gap. Looks bad but works. I don't know if you will have room to do so with the cats, but It's worth a look. Caymon __________________ '90 GT Under construction Best E.T. = Fast @ High Speeds - OK So I Lie. So What!!! 04 F-150 STX 4.2L 5 spd Rice Haters Club Member #128

12-13-2002, 01:23 PM	#5
RED92LX50 Registered Member Join Date: Aug 1999 Location: Fairfax, VA Posts: 220	maybe... If you are sure the leak is at the header/h-pipe junction, you may be able to put a bead of muffler mender around the joint to stop the leak. It is smilar to using plumbers putty on leaky pipe joints. I used it on one of my connections and have not had any problems in over 6 years. Otherwise, maybe the leak is at the heads - in which case you can retorque those bolts (as they can loosen a little after the inital install with the first few heat cycles). __________________ 1992 LX 5.0 Convertible Red/Blk Gears, Exhaust, bolt-ons... R.H.C. #51

12-13-2002, 09:39 PM	#6
1991GT Registered Member Join Date: Jul 2002 Location: Flemington, NJ Posts: 13	Thanks for all the help. I can't work on it tonight because it's raining but I should be able to work on it over the weekend. I'll keep you guys posted. __________________ '91 GT - 135K miles T-5, stock 2.73's uugh, MAC cold air, Pro-M Bullet 75mm, BBK 1 5/8 jet-hot unequal shorties, BBK h-pipe w/ cats, Flowmaster 2 chambers, Pro 5.0 short throw, KYB shocks and struts In the garage waiting to be put on: Screamin Demon coil, Dyna Mod TFI module, underdrive pulleys

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