Cracked exhaust manifold...easy to replace?

I just found the classic cracked exhaust manifold. Its cracked right before the joint where it meets the downpipe.

Is this a rather easy thing to change? It looks like the exhaust manifold is literally right on top (somewhat embedded from the fuel rail)

I'm a noob. :banghead: :repair:

I just replaced my "cracked" manifold on Sunday. It really wasn't a difficult job just time consuming. Make sure you get new O-rings for the fuel injectors too. I couldn't get in there with a torque wrench to torque the nuts back down so, I just made sure they were nice and tight. If you don't have a "Haynes" or "Chiltons" pic one up! and make sure to wet the new O-rings with fuel prior to reseating them. Chris

For some, there can be trouble with the studs threaded into the block at either end of the exhaust manifold. They are known to shear off, like the shock bolts. The rearmost stud on #6 is the one you dont want to break. Drilling it out is best done on a engine stand.

Its a good idea to heat them and soak with penetrating oil before trying to turn them. I dont use a torch anywhere near the fuel lines. Just start with engine warmed up, with gloves this job can be done on a hot engine.

The exhaust manifold collector nuts are often rust frozen, and a small propane torch works well to get them loose.

I'm assuming this is the 6 cyl. I helped my brother change the cracked exhaust manifold on his Jeep Wrangler. He bought the cheapo replacement off e-bay, with the bellows welded into the two outer most tubes, to handle the expansion/contraction without cracking. Its seems to work, he hasn't had any trouble with it since.

He drove it for a while before we replaced it, so I had him spray WD-40 or penetrating oil onto all the studs after each time he drove. As well, we bought new exhaust studs, figuring we did NOT to re-use the old ones, its worth the $7 total cost for 2 studs and their nuts. (That was ordered from an online discount dealer, NOT a local dealer that will probably want twice as much.) The heat cycling with Penetrating Oil, the week he continued to drive was perfect, all the bolts and studs came out without a problem.

You have remove the intak manifold with the exhaust manifold. Most of the time was spent cleaning up the manifold and head flange surfaces for the new gasket. (ScotchBrite Pad, be careful on aluminum, its soft enough that overdoing it with a scotchbrite pad can mess it up) We also used some Copper Gasket Spray on the manifold gasket.

We were able to re-use the injector "O"-Rings, but I'd recommend getting a new set, they are not that expensive. We sprayed WD-40 on they seals before disassembly, and put engine oil on them before re-assembly. Lubricating the "O"-Rings prior to pulling out/pushing in what ever its sealing does a lot to prevent damaging them. But its common for old "O"-Rings to get damaged when you take them apart.

It took us an entire Saturday to do the job, and we had never done anything like that before, plus we weren't rushing, we stopped and did other things during the day. I've got a lot of experience on other vehicles doing things like this, so if you don't, I'd give yourself an entire weekend to do the job.

Rick Anderson said:

The heat cycling with Penetrating Oil, the week he continued to drive was perfect, all the bolts and studs came out without a problem.

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the manifold bolts on my 89 fall out or loosen on their own.

And in that case the penetrating oil can't hurt.

I had rebuilt 440 V8, I did my penetrating oil before and after driving trick for a week before pulling the motor. All the bolts/studs came out without effort, except one stud I did NOT see while the engine was in the car, thus it never got the penetrating oil. That stud was seized and snapped off during removal.

I'm not sure if you just kidding around, because your studs are that bad, or you don't believe it will work. But I suggest doing it, because it can't hurt to do it, and might avoid a broken or seized stud which we all know is a huge Pain In The A$$.

You might consider just leaving the fuel rail and injectors in place - and just disconnecting the fuel and return lines. Thats what I've done on 3 XJs so far.

I thought we ran into some sort of problem that made us remove the fuel rail. I can't remember, I thought it had something to do with the throttle cable.

Either way, I think everyone will agree, avoid pulling the fuel rail if you can, if do have to pull the fuel rail off, be aware that may damage some of the "O"-Ring seals. Using some oil on the "O"-rings before and after may help avoid the damage. You should consider getting some new "O"ring seals if you end up having to pull it.

i've had mine off to install aftermarket header, and if you have never done it, it's kind of a pita. a crack as low as you describe, i would try to weld it, or apply some Thermosteel, or some of that paste muffler shops use. of course it might not last that long, but it's easier and much faster. if it's past the collector tubes, you could maybe hack it off and weld on a new custom piece.

X2 on the thermosteel if it isn't too bad or large of a crack!

Or

Try

PERMATEX® Hi Temp. Metal Repair Compound
Makes long-lasting repairs to high-temp, low pressure exhaust leaks from the exhaust manifold to the muffler. Gets stronger with heat up to 2000°F. One part, water-based ceramic is safe and easy to use.

Suggested Applications:
Cracked and broken exhaust manifolds, headers, furnaces.

I've never used that but it sounds like it should work with a temperature rating of up to 2000 degrees.

Took mine off and welded it up a couple months ago, not looking forward to doing it again. Its not hard, just time consuming as can be.