2.5 liter exhaust manifold - banks - Cracked again!

[97 TJ - I dont wave]

 

The facts first:
97 TJ 2.5 liter
33x13.5 tires with 4.88 gears (4 inch lift)
magnaflow cat with maganflow muffler
K&N air filter
180 degree thermostat and the "Flow Kooler" water pump.
no mods to engine or computer.
148,000 miles, original owner.
It's also rhino lined, bumpers, winch and bla bla bla...

The Problem
I replaced the stock exhaust manifold due to a crack on the back side (facing engine).. I went to Napa and bought another manifiold which cracked in the same area 2 or so months down the road. I went and exhanged this one at Napa for another and it cracked in about 2 months again in the same spot. Frustrated I went a bought a Banks header. The Banks header cracked after 6-7 months down where the tubes all meet near the flange under the jeep. It cracked on a weld and also, if you looked inside the flange you could see small pinholes through the joints. I sent this one back to Banks and got my replacement. I put the replacement on in March of this year and this last week found it cracked again. one quarter of an inch of the weld at he flange blew out, this is the side of the flange that faces the engine again. I took off the header and looked inside through the lower flange and found, again, two small pinholes as well as the weld that blew out that I just described. I took the header over to my local muffler shop (one of the more respected ones here in Seattle). They said that it looked like the header was getting too hot and that is why it was cracking. They pointed out the discolored metal on the lower flange area. They did put a weld (temp fix) on the holes but say it will probably blow again because they think the metal has been weakend because of extreme heat. They refered me to a respected speed show in town to see if they could reflash the computer to get the exhause to run cooler. I went over to the speed shop and explained the issue and showed them the Banks header. They said that since my engine has NOT been modified (ie bored out, pistons, etc) and that I had 4.88 gear to compensate for the tires they didn't think that my exhaust should be a problem. They did say I could have a bad up stream oxygen sensor, but they could charge me an arm and a leg to let me know if I do. I said no thanks and left. On another note, my exhaust pipes are not binding or pulling in anyway on the header. Also, when I down shift I get rumbling/poping out of the exhaust, but it has always done this. I know Jeep exhaust manifolds have a reuptation for cracking, but why have I blown through 2 Banks headers? I spoke with a Banks Tech and they said they did not know either but they will gladly exhange my header again. I will hold out until the weld blows again I guess.  Does anyone have any idea why this is happening??
Thanks....
RC

[aw12345]

Retarded ignition timing can cause the exhaust manifold getting to hot. I don't honestly know if a 2.5 has a timing chain but if it does would not hurt to check how much slop it has. Provided it has timing marks line those up take the distributor cap of and turn the cranckshaft back and fort to make the rotor move if it takes more than 10 degrees of crank rotation to move the rotor just barely back and forth the chain has to much slack atleast that is recommended for v8 engines should be the same for a line 6 or line 4 engine. However headers do have a tendency to run red hot especially when the engine revs fairly high on the highway and subsequently do not last all that long

[Desert Bob]

Do a plug check to see if #4 is running lean. 

[97 TJ - I dont wave]

 I checked the timing chain today and there seems to be no play in comparison to the rotor rotation. I pulled all the plugs and they are all wearing the same and not of odd color. I am thinking of buying a new upstream O2 sensor and see if that does anything in the long run, thoughts?
 

[Jeffy]

The 2.5L has a rough idle.  It's rougher then the 4.0L.  I know of several instances where the 2.5L has broken off OBA brackets.  It just fatigues them at the welds.  This is why Kilby doesn't sell the older OBA kit anymore.  My support bracket broke off and flew into the fan.  Luckily, it dodn't damage anything else.  I've also had exhaust hangers break off.  In total, 3.  It was worse when I had poly engine mounts since those transmit a lot more vibrations.  That's one of the reason I went back to rubber mounts.

I'd look at all the hangers and see if you can free them up.  What's happening is the engine is vibrating at a different rate then the exhaust and it's breaking at the Y.  This is why many small I4's use flexible joint at the downpipe.  It might be something to think about.

[97 TJ - I dont wave]

 
Good points, I think I will try puting the stock motor mounts back in and buy the 1 inch spacers for them. My 1 inch motor lift spacers to create alot of vibration. I'll give that a shot... thank you

[Jeffy]

Good points, I think I will try puting the stock motor mounts back in and buy the 1 inch spacers for them. My 1 inch motor lift spacers to create alot of vibration. I'll give that a shot... thank you

That's exactly what I ended up doing.  I went with the JKS 1" spacers.  I had a Currie 1" MML and a TDP 1" and still went back to stock and the spacers.  You'll notice the torque difference when starting off the line.  It's not as firm as you can feel the engine rock rather then you taking off.

[97 TJ - I dont wave]

I am getting ready to put Banks header # 4 on. I have taken the Jeep to the dealer and they said the engine is running according to the manufacuters specifications and that all is well..  I called Jet and asked them if their stage 2 would help cool the exhaust and received a "yes". The stage 2 chip is my next purchase and then I will send my 3rd cracked header back to get my 4th under their life time warranty. Oh, I also purchased a new Accel Performance Coil.. . Didn't help. So hopefully when I put on the Jet Chip it will help the 4th new Banks header. I also got rid of the lifted motor mounts and went back to the stock mounts with spacers.. This is killing me... One positive is that I can now replace a header in about an hour and a half.
 

[Bounty Hunter]

I know Jeep exhaust manifolds have a reuptation for cracking, but why have I blown through 2 Banks headers?

The 4.0L has that reputation, but not so much on the 2.5L, or at least I haven't heard of many.

I'll have two good OEM manifolds available once I get my Borla header on.

[Mr_Random]

why are you running it with the cooler t-stat and "high flow" pump? Engines have a designated operating range for peak thermal efficiency, messing with that (at least in the fuel injected age) will cause any number of unforseen troubles. Due to the cooler t-stat, your control system is probably running in "warm up" or "seek" mode constantly, with richer a/f mixes and a retarded timing. I can't say this is a direct relation to your header problem, but it might just be! Just as good measure, go buy the correct t-stat and put it in, it's one of the cheapest parts anyways.

If you're having overheating problems and that's why you've messed with the engine cooling, just get a better radiator. I know it's cheaper to get a thermostat rather than a radiator, but if you're not gonna do it right, don't do it at all...

[97 TJ - I dont wave]

No, I bought the thermostat due to the future plan of installing the JET chip.
At this point I have not exchanged the header for the 4th one yet.
I have replaced the motor mounts and put my stock ones back in with 1 inch spacers, but that hasn't helped.
Like the dealer said, my engine runs just fine. I am at 165,000 miles now.
I almost wish it wasn't running so good so it would blow up. I think I could sell the HEMI swap at that point to my wife. Either way, when I get the new header I will change both oxygen sensors, and put in the JET chip. I will update all after that.   Now that I think of it, I have almost gone through as many Banks headers as I  :bore:have windshields....

[97 TJ - I dont wave]

Bought the Jet Chip Stage 2 and installed it. I still get rumble out of the exhaust when I let my foot off the gas and when shifting between gears (lean I assume). I will order the #4 next week and install it and see how it goes from there. If this chip doesn't work I have no idea what to do next...... 5.7 Hemi swap maybe?

[Castr8r]

I think Random has a valid point.  The engine is designed to run at a certain temp for many reasons, and changing the t'stat to "help cooling" may well screw it all up.  For what it's worth, I had a 180* in my '89 and noticed an improvement in performance and driveability when it went bad (after 4 mo...), and I replaced it with the 195* Jeep calls for.

[whitejeep94]

hey man what kind of plugs r u using because if your using anything other then champs your temp will go up causing the change in color hint craking your heads. i ran like 4 kinds of plugs in like a two month tryin to pass my smog CA/ now its a grows pol. get the O.E.M

[cwildmann]

I would go back to the flex pipe idea as I've heard of that being the solution to prevent the 4.0l header from cracking.  For $40 it can't hurt to try.  I guess try to install it on the downpipe before the cat? - probly have to cut out part of the downpipe and then strap on the flex pipe.   Anybody install one before and what location did you use?  Also what is the diameter of the downpipe?

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