Crack in exhaust manifold


#1

I have a crack in the exhaust manifold on my 2000 Xterra (127,000 m). Very expensive to fix and I don’t THINK it is causing me problems other than a bit of noise.

Is this something that will cause other problems down the road if I let it go?


#2

Yes. The crack allows exhaust gases to escape, which is why it makes noise. The escaping exhaust gases are AHEAD of the passenger compartment, and can easily be drawn in through the ventilation system.

This could make you sick and has the potential to be fatal. This is not a money issue, it’s a safety issue. You need a new manifold, or a used one from a junk yard, to replace the cracked one.


#3

You could also try a J-B Weld fix. In any case, you’ll need a new exhaust manifold gasket. With the J-B Weld, remove the heat shield (use lots of penetrating fluid on those shield bolts or you’re sure to break one or two of the studs/bolts). Carefully loosen the manifold bolts. Use penetrant here too. Once you have the manifold off, follow the J-B Weld instructions carefully. A corase wire wheel followed by a fine wheel run along and around the crack will get you going. Then mix and apply the J-B. Let it set up properly. Then after about 6 hrs. at room temperature, you can set a clip light with a 60-watt bulb right near the crack to aid curing. When putting the assembly back together, don’t forget new “donut” gasket(s) if needed. Reverse procedure to re-install and use a torque wrench for setting the manifold bolts. DO NOT OVERTIGHTEN or you could re-open your repaired crack or cause a new crack. On Toys, when you ask around at the junk yards, (now P.C.–auto recycling centers) specify exactly what your engine model is, i.e.: 4AFE or 4AFG, or the like. Usually found on a sticker under the hood. But do repair it soon, both to keep you from getting carbon monoxide poisoning and to save your valves on that cylinder. Valves require a little back pressure to keep them from crashing on the valve seats and cracking the valve face, or worse. (Submitted by Prof. Handy).


#4

Do not use J-B Weld. It only works up to about 500 degrees F, and the exhaust manifold gets much hotter than that. I believe on the J-B Weld site it even says to not use it on exhaust systems because they get way too hot. I suggest taking it to a decent exhaust/muffler shop, have them fix it. I think it’s worth paying someone to, because it’s probably a PITA to do yourself. But it is something you need to get fixed soon.


#5

If this crack is accessible and is not against the manifold/cylinder head flange, then a good welding shop can probably fix this without too much trouble. Cast iron can be welded and it will hold.


#6

The problem is it WON’T correct the problem. The crack was probably caused by warpage (it’s known problem Nissan had from 1999 thru 2003). Welder may fix the crack but the manifold will still be warped and NOT sealed right.


#7

Note I qualified my answer by stating a welding shop could easily fix this IF it is accessible and IF the problem is not on the manifold/cylinder head flange.

They can crack anywhere and I have no idea where this one is cracked at.

The word “crack” does not mean a warped flange and I’m taking the word literally.


#8

Just have the shop check the flange for flatness before attempting the weld job. If it’s minor enough, it can be machined. If not, it can be discarded.


#9

Had a crack in the manifold of my Toyota Pick-up. Picked up a replacement manifold at a junkyard for $30. Never had the problem again.