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my1stjeep 07-01-2009 06:14 AM

Exhaust Question
My 89 4.2L YJ has a broken exhaust. It rusted through right after (engine side) the cat. The pain is that the exhaust is all welded together. So I went and bought a new exhaust system and am getting ready to put it in, until i look and see two other pipes that are welded into the pipe that runs from my cat to my exhaust manifold. they are welded in and run up towards my air cleaner. not being a welder, my question is: is there any way i can put a new exhaust system in and not weld those two lines into the new system? And what do those two lines actually do? Thanks in advance

dwnbylaw 07-01-2009 09:50 AM

Sounds like its the 3/4in bypass from the cat to the exhaust manifold. Im in Texas and mine is a deer lease jeep, so I just welded them closed. Your emmision in MA. may not allow you to do that, but if its a crawler you shouldnt need do have to cap it or bend it over maybe weld it, cause if you dont it will sound like the biggest exhaust leak ever...

NAVYCHIEF 07-01-2009 10:45 AM

i had mine(89 and90 yjs) welded. no difference in performance. got rid of the constant ticking. there are valve thae go on the large pipes. very expensive. if you can do away with them i would.

my1stjeep 07-01-2009 12:00 PM

since it's an 89 i won't have to pass emissions which is good, but i just want it to be quiet enough not to get pulled over (which by installing a new system, it will). i am just worried about screwing up something by capping them since it's my DD.

thanks for the imput

kik 07-01-2009 02:27 PM

I have an 89 4.2, 5spd. When I replaced the exhaust system and Cat I got the Air Assembly Kit that attaches to the Cat from Quadratec.

my1stjeep 07-01-2009 02:59 PM

kik, where did you pick that up at? sorry for my ignorance, but where's the 'Quadratec'?

kik 07-01-2009 03:33 PM

Go to Jeep Parts, Jeep Accessories & Jeep Soft Tops From The Jeep Parts Experts - Quadratec
They sell Jeep parts. You want the Dynomax Catalytic Converter Air Tube Kit. They have it for 29.99. I think this is what you are looking for.

my1stjeep 07-01-2009 04:26 PM

now the real question is: how bad would it be to just cap the hoses and let it ride?

buckshot500 07-01-2009 08:09 PM

Running an invisible cat, I cut the small tube just below the exhaust manifold connection. Leaving about 4" of the 3/4" tube, I used the 3/4" U-bolt clamp from the cat end & a copper sweat cap from the plumbing aisle.

Can't remember what size it was, but I bought a few sizes near what I thought & returned the unused ones. The copper cap fit inside the exhaust tube.

The other line coming from the air cleaner to the cat was omitted.

The other U-bolt from the cat needs to be saved, since you won't find one anywhere. PB blaster did the trick.

my1stjeep 07-02-2009 07:47 AM

thanks buck. much appreciated

Levinoss 07-02-2009 08:05 AM


Originally Posted by buckshot500 (Post 395677)
Running an invisible cat,

Basically you bypassed the cat is what you are saying?

daddyjeep 07-02-2009 05:10 PM

Those tubes are there for emissions reasons. I ran with mine capped off for years until I moved to an area where emissions testing was required.

buckshot500 07-02-2009 07:14 PM


Originally Posted by my1stjeep (Post 395783)
thanks buck. much appreciated

Your welcome, Just be sure about the inspection waiver before cutting anything. Even then, federally speaking it's not exactly leeegull.:banghead:


Originally Posted by Levinoss (Post 395785)
Basically you bypassed the cat is what you are saying?

Did I say that?:confused::D:rolleyes:;)

That kitty puked it's guts out anyway, so I put it out of it's misery.:wavey::punk:

Meantime I used a test pipe. When I'm all done testing, I'll post the results here in this thread.

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