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anyone have thousands of miles on a cracked manifold?

S

snow drifter

NAXJA Forum User
Location
Saint Mary's Glacier, CO.
Has anyone had any ill effects, major problems, from driving with a cracked manifold? It seems numerous people even have aftermarket headers still cracking and the cost and time involved with removing and sending back to the manufacturer is crazy. I bought my XJ with 50K on it and I first noticed the crack at about 80K. I now have 138K with the same small crack. Hasn't got any larger with no problems. Gas mileage and power is the same as when I first bought it with 50K. I don't have any plans to change it unless of course the crack gets much larger and it starts to get loud. Can anyone tell me why I should drop 300 to 500 dollars for a new header? What could running like this hurt, and has anyone seen first hand any damage done to a motor running with a cracked manifold. Thanks
 
I was told by a mechanic that it would do damage to the valves woth the crack(s) that i had in mine. I asked around, and time after time I have been told by people that own Jeeps that it will not affect the valves, but just be aggrevating to hear the noise. I had mine welded while I had some head-work done. It is holding-up just fine. My 09 Xj has 192,000k on it.
I had asked the previous owner how long it had the crack/leak, and he said about 4 years or so
 
ive put about 4k since i noticed the crack. so far nothing has gone bad *knock on wood*
 
Hey guy's thanks for the responces. I have also heard about the valve thing, but have never known anyone who has ever had valve damage. Is that just a bunch of :spam: ? Anyone else have any problems? Lets here it! A lot of people spending some big money for replacement headers.
 
I bought a Grand Cherokee with a cracked manifold w 90000 miles. It would "close up" when the engine got warm. I finally replaced at 130k, because it got worse. I now have 160k on it, no problems. Bought a 90 4x4 Comanche with one in 3 pieces, so I had to replace it right off, but no telling how long the PO had it on there cracked. I think he parked it because of it, ( a $100 part!)250k on this truck, still going. knock wood. Bought an 89 Comanche, with the same thing, just replced it, 150k on it. I say don't sweat it until it gets annoying.
 
XJRob2 said:
My 09 Xj has 192,000k on it.
Click to expand...

Damn dude...that's a lot of driving. :scared:
 
I've put around 50k on a cracked manifold on my 95 and it was cracked when I got it about 5 years ago. No problems.
 
When my engine went in my 98 it had over 330,000mi, it too had a crack but I never noticed it till the engine was out, we just welded it and on the new jasper engine it's been fine for the 12 months it's been in.
 
How about the possibility of the o2 sensor getting a skewed reading from the introduction of air into the exhaust flow? Not trying to steal anyone's 'thunder' here but, if you really have to ask maybe it's not such a good idea.

The yards my way have several 'crack-free' exhaust manifolds as I type this so I know they are around. The major contributor to exhaust manifold failures are worn motor mounts and tranny mount coupled with a lead foot. For all the Renix folks such as myself, a visit to the salvage yard is all it takes to upgrade to the high output exh. manifold and down pipe. :shhh:
 
My xj has had a cracked exhaust manifold for about the last three months, and other than the irritating noise I have no ill effects yet.

I drove my pickup with an exhaust leak for a summer about ten years ago, and burned two exhaust valves.. the whole valve thing is real. :)
 
Besides the valves like mentioned, a large crack could throw off the oxygen sensor readings resulting in the Jeep running too rich. This could cause increased catalytic converter wear, worsen gas mileage, increase engine wear from unburnt gasoline washing cylinder walls and entering the oil, increase upper cylinder carbon deposits and raise underhood temps from the hot exhaust causing failure of heat sensitive components. The Jeep will also pollute more as the exhaust bypasses the converter and runs too rich. The vehicle may fail tailpipe or visual inspections (where applicable).

All this is completely based on assumptions and conjecture btw. These are pretty durable motors so I doubt a small crack would have many effects but I think it is part of good engine maintenance to repair manifold cracks. My idle is noticeably smoother after replacing my badly cracked header.
 
I meant my 90 Xj Laredo, not my 09. Yes it has a lot of miles on it, I got it about 4 months ago for $800.00 so I can't complain. I plan to get an exhaust system when I do a motor swap, which I hope is no time soon.
 
Last edited:
I don't know exactly when it cracked, but I think I have been running with a cracked wxhaust for about 3-4 years at least. I have 143k miles on it now. I have been told by mechanics that it needs to be fixed before getting it inspected, but I have yet to fail a single inspection, even the new one last year when Texas introduced emissions testing to the mix. I have heard that the excess heat in the engine compartment can wear out the driver side motor mount. To date, I have had no problems.
 
Slo-Sho said:
How about the possibility of the o2 sensor getting a skewed reading from the introduction of air into the exhaust flow? Not trying to steal anyone's 'thunder' here but, if you really have to ask maybe it's not such a go :shhh:
Click to expand...
I don't know, I'm still on the origonal o2 sensors on mine and it has thrown no codes, gas mileage is great, and idles perfect. Well, I think I'll keep my stock manifold on for a few thousand more miles. If it cracks any more and starts to get loud, I'll start looking for a replacement. I think what we've learned so far is with a small crack, it really wont hurt a thing!
 
1990 with 4.0 engine and a small crack in the manifold- I can't see any ill effects. Now, about this claim that a crack can let oxygen in, resulting in the oxygen sensor richening the fuel-air mix: the pressure inside the exhaust manifold is much higher than air pressure outside, any leaking will be only from the inside to the outside. I don't buy that oxygen will get in with the engine running.
 
When we fixed my cracked one we drilled a hole at either end of the crack then welded it, hopefully it relieved some of the stress in the faulty area and it won't crack again. Just for info my friend and customer who has a pretty big repair business says that on an average he welds about a dozen exhaust manifolds a week, not just on jeeps but on almost all the new cars, they have gone from the old style cast mainfolds to steel tube header types to save on weight so it's a pretty common thing now a days. How hard it is to weld in the vehicle is totally dependent on where it is. Mine was on the inside and while he could have welded it in vehicle we could not have drilled the stress relief holes.
 
Mine has over 310 K on it, and it also has a cracked manifold. Runs & drives fine.


As to the crack, I'm with 4XBob...Not so sure how a cracked manifold will dilute the exhaust enough to affect the O2 sensor, as the manifold will be pressurizd with the exhaust gases. Sorry, but I fail to see how air can get IN the crack when exhaust gases under pressure are coming out (which is what makes the noise).

Only issue my engine has (and I seriously doubt it is crack related...lol), is #2 cylinder runs dirty, ie the plug fouls every now and then.
 
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