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Jeep 2.5L exhaust manifold keeps cracking

S

Schris1

NAXJA Forum User
Location
California
I have an 86 Jeep Cherokee w/throttle body injected 2.5L engine. The exhaust manifold keeps cracking within a year after replacing it. It's too expensive to keep replacing it. I've tried factory cast iron replacement, cheap tubular style, and an aftermarket "improved, lifetime warranty" factory style cast iron all without success. Anybody find any solution to this? Thanks.
 
Motor mounts worn? That could cause the engine to move too much for the flex of the exhaust components to handle.
 
I to have a 1986 jeep wagoneer with a 2.5L TBI and i just noticed a leak also a ticking and when warm it disapears. I found a header from pacesetter for a 90s model CJ and a TJ with a 2.5L with the egr hookup and a oxygen sensor but i dont know if it will fit mine and yours application. I have also thought about trying to fab one. But i am unsure how to go about it. But if you find a fix please let me know as i will you.
 
By the way where did you find a aftermarket one for it. I may try this route with some improvements to it. Tubular may work if i can improve the fit or beef up the connections. You know i just thought of something our engines have a shock on the front of the engine maybe this device is suppose to stop the engine from moving to much. This flexing would definatly crack the manifold at some point. Just where is yours cracking at. Bro i think i am on to something here that may cure both of our problems.
 
My motor mounts, trans mount, and exhaust hanger are all good. I've even gone so far as to make a bracket that mounts to the trans and hold onto the exhaust pipe. I'm not convinced that motion is causing the cracking problem. My manifold typically cracks in the center area. I've even had it crack all the way around the outer manifold tube and it fell apart when I removed it. I'm not sure if the hot air intake cover over the manifold is causing some or all of the problem.

I've seen factory size tubular exhaust manifold on www.bankspower.com. It is for later models and would need to be modified to have at least the EGR hookup for earlier model Jeeps. The tubular style that I bought was about $150 from a Jeep supply place. I've also seen them on the internet for less. I wouldn't recommend it. The weld inside the flange which makes the hole smaller. Also, they bend the tubing versus mandrel bending like Banks does.
 
Here is what i have done so far. I contacted Hooker Headers only because they are close to me about making me a header dont know how much it may cost but it may be worth it. Only because i intened to replace my 2.5L with a long block setup and keep my jeep until time ends or until wheels fall off. Sharis how many miles you got on your mill. I have a place that offers a 7 yr or 70,0000 mile warrenty on there long blocks. So if you plan on keeping your rig then this could be a good investment in a header for it. Or we may be able to get a newer header and have a machine shop setup the EGR and oxygen senor to work with our setup either way having two jobs to do is better than one setup. What do you think about this.
 
Contacted Banks and they sent me the PDF installtion file for the wrangler header and talked with one of the engineers. By the looks of it we may be able to do the mods to it that we need the two inner cylinders exit straight out and then bends down to the flange going straight down. Banks is here in Azuza CA looks like a road trip for me to gaze at these wonders and do some measuring. But they do cost like 400.00 plus the machining and the cutting and welding of the boss for the EGR and Oxygen sensor. What do you think.
 
now that sounds like a plan but you better check the head pipe first. What you posted as a link is for a 4.0 and i dont know if it would work for us seeing as how we have 2.5L but it might might have to move a hanger or something but who cares. 100,000 shoot man you got a lot of life left on yours mine has 221,000 on it and is a little sluggish till i hit third gear then it gets crankin. I am going out to banks as soon as i can and will keep you posted. Also looked at clifford but they look a little flimsy to me.
 
The word I got from one of the guys at Banks was that Jeep manifolds crack because their exhaust runs too hot. I don't have a solution as of yet.

I used the 4.0L as an example for where I might get the O2 sensor placed.

Do you still have the stock fan clutch setup? If so, lose it!!!!! I replaced my fan and clutch setup with an electric fan. What a difference!!!! My Jeep had more power and it ran smoother and quieter on the freeway.
 
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I would pull it off and weld it, then wrap it with exhaust wrap to cause it to cool down more slowly so as to stop rapid thermal contraction of the manifold that could crack it.

I have had some experience with cracking manifolds in 2.5L Pontiac Fieros. I found that the welds were thin, and in areas that naturally would have a high degree of expansion and contraction. Because of the shape of exhaust manifolds, branching off like they do toward the manifold and higher temperatures, they have to be welded properly and carefully or they will naturally crack. By my improving the welds, I can stop the cracking and then an exhaust wrap will end the problem.
 
Hmmmmmmm never thought about the fan clutch makes sense tho since you rob the engine of power with the pully system. I have built engines for years and made power with mods to heads and blocks. I have been interested in doing a throttle body bore out for our engines to try and see where that goes might be a good add on with the Banks header. I have been involved with machine shops and design shops all my life. So if you have an idea lets roll it around and see where it goes. What about our header pipes could they bend us one of those to.
 
I read that exhaust wrap is very bad because it holds in the heat and causes the manifold to burn up or rust from the inside out. That's why manufacturers won't warrantee their headers if you use the stuff.
 
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