Jeep question

[Chuck52]

This is the only discussion group to which I belong....a fact I am rather proud of. And since just about any subject seems to be acceptable for discussion, I have a jeep question. I'm going to Florida to pick up my Navy son's '97 Jeep Wrangler Sahara before he ships out for a six month pleasure cruise. He just informed me last night that the new exhaust manifold I thought he had installed is actually in the back seat, where it presumaby does little good./w3tcompact/icons/eyes.gif The manifold on the Jeep is cracked; apparently a common problem for this model. One of my buddies has a horror story about driving a car with a cracked exhaust manifold. Seems the crack allowed cold air to come into contact with hot metal where it is not supposed to, and cause severe engine damage. My son has driven the jeep for a few months with the crack with no problems, but he's in Florida. I will be driving it to Missouri. His mechanic friend says there should be no problem except for a bit of noise and maybe slightly worse, or maybe even slightly better gas mileage. Anyone got experience with this stuff? I know crackpots, but have no experience with cracked exhaust manifolds.

Chuck

 

[Jeff396]

I'm no mechanic, but wouldn't a cracked exhaust manifold just cause hot air to blow out...not cold air to be sucked in. I had a friend in the 70's who drove a company van for his dad's business. Thing ticked all the time with an exhaust leak resulting from a gasket problem. I don't think it caused any problems other than being very annoying. Can't be too much different that a hole in the muffler or header pipes. Now if it were an intake manifold you'd be messing up the mixture and may in fact cause problems. Anyway, just my opinion.

Jeff

 

[RobertN]

Probably the worst you'll see is a lean condition on the cylinder next to the crack. It may throw off the computer and fuel injection system, sense the Exhaust Gas Sensor is down the exhaust pipe from it, depending on how bad the leak is. I know here in California, they pick stuff like that up on the smog checks, and most of the time it causes them to fail the test.

You may actually get worse mileage, because the computer will try to compensate for the lean exhaust condidtion.

If you run it, be really careful about the fumes. You don't want to be on a long trip, smelling and inhaling the fumes the whole time, especially with the windows rolled up and all. People die from smelling to much of the exhaust...

 

[Chuck52]

Thanks for the replies. I think my buddy's problem occured when he shut off the engine and cold air came in through the crack hitting surfaces which would normally be protected while they were hot. That's how his mechanic explained his engine damage anyhow. Sound possible/likely?

I will be doing pretty long trips to get it from FL to MO. Stopping in Tennessee to see the folks and then continuing after a day off. However, it has a rag top, so I expect to have plenty of ventillation. I'll be aware of the carbon monoxide problem, however. Thanks for the reminder.

Chuck

 

[Jeff396]

Assuming it's a four, how hard would it be to take some tools and swap it out? Being that it's so new and that it's spending time in the south, it should come out easily. If it's a V6....forget I mentioned it. Maybe there's someone local who would be willing to replace your part if you explain the situation. Exhaust manifolds are not exactly tough as long as it's not one where the engine has to be lifted a bit to remove it.

Jeff

 

[Chuck52]

It's a six. I haven't looked at it, but it sounded like it wasn't easy to get to. Does it require pulling the engine?

Chuck

 

[s1120]

That would be an inline 6 in that. You will have to take the intake off also. I don't think you would need to pull the motor. Not that bad of a job.....unless the studs snap/w3tcompact/icons/frown.gif

 

[RobertN]

It's not particularily hard, but it's not really simple. It sounds like your tools and garage are two days away... which would complicate things...

 

[Chuck52]

Yup. I plan to drive it back to the great state of Missery with the cracked manifold. That was the purpose of my original post....to see if anyone thought that would cause engine damage. I'll probably pay someone to install the new manifold when I get it back here. I just spent a pleasant day working on both my old F150 and my Dodge Caravan, reminding myself why I didn't become a mechanic.

Chuck

 

[Jeff396]

I agree, a cross flow head with the exhaust on a side by itself could have been done with a few hand tools. However once you get into the intake side on a reverse flow head it's hard to anticipate what you would need before hand. Sometimes you need special tools as space to get to some of the bolts can be tight. Does your son know anyone who lives there and could maybe give you a hand? Maybe there are some TBNers in the area that might like to lend a hand fixing a Navy kids car. I love to do jobs like this on other peoples cars...especially since it doesn't cost me anything./w3tcompact/icons/smile.gif

Jeff

 

[Chuck52]

Jeff,

I'm on a short time string for this little road trip. No time to work on it down there in sunny Florida. My boy's on the JFK. You may have read about their adventures getting combat ready for deployment to... wherever the next place is which requires an attitude adjustment. I had a brief time frame in which I could zip down there, pick up the Jeep, maybe see the boy, and drive back here. Now it's not clear just where the ship will be when I get to Mayport, but at least picking up the Jeep has been arranged for even if sonny boy is out playing in the ocean. When I get it back home I'll look at it to see if I think I can reasonably do the job myself. I'll at least have six months before he comes looking for his baby. Some of you guys think you're attached to your tractors, but my boy is <font color=red>really</font color=red> attached to his Sahara.

Chuck

 

[RichS]

I can relate to him being "Attached" to his Sahara. I bought mine new in 1989. Although it is no longer my daily driver, I don't think I will ever get rid of it. /w3tcompact/icons/smile.gif

 

[MarkV]

Chuck,

I am about as far from being a mechanic as one can get./w3tcompact/icons/smile.gif Although I did have an old Chevy Blazer that had a V8 with headers on it and a small hole developed about 2” from the exhaust port. I was told that as the colder than normal air was drawn into this hole it caused a valve to warp. Of course they would probably tell me anything rather than back the engine they built.

Might be worth a stop at a Jeep dealer and talk to the service Manager.

MarkV

 

[Rowski]

Chuck

I think jeep came out with a better designed exhaust manifold. I have changed a few manifolds on those in-line 6 cylinders. You need to remove quite a bit of "stuff" including the intake. As other have mentioned, a cracked manifold can: You can get fumes into the passanger compartment. Add oxygen to the exhaust upstream from the lamda (oxygen sensor) sensor which can mess-up the fuel management and possibly set the "check engine light". Have hot exhaust gases (if crack is bad enough)directed on brake lines, wiring harness, hoses, etc.

I would love to change a manifold on a southern car. The last one I did was a 1996 jeep and I had to do a lot of heating and got bloody knuckles!

 

[Joe_W]

In my previous life I was in the auto service business in a Chevy dealership as a parts manager. I have seen burnt valves resulting from broken, cracked, and gasketless exhaust manifolds. As has been suggested before, the damage doesn't occur while you are driving, but rather as the engine is cooling. If a portion of the valve cools quicker than everything else, it will lose its temper ( no it won't get mad, it will soften the metal). Then when you get the engine up to operating temperature, that softer area on the valve will burn away, leading to an expensive repair involving removing the cylinder head. If the crack is small enough and you feel real lucky, you may get by. If it's a possibility, you may want to consider putting it on a trailer and taking it home. Good Luck!!
Joe W.

 

[Anonymous Poster]

If the crack is in a spot you can get to, use some plastic furnace cement to close it up. Let the cement set up a few hours before you start the engine.
I know of a few that have made it all the way to the crusher with furnace cement on exhaust manifolds.

 

[Chuck52]

Thanks Franz. I was wondering if there might not be some kind of temporary fix possible. I seem to recall a kind of tape you used to be able to get for fixing holes in exhaust pipes and mufflers. I'll try to find some of that furnace cement and hope the crack is where I can get to it. Is it something like a high temp J-B Weld? I've fixed a number of things with that stuff, but I doubt it would take the heat of an exhaust manifold.

Chuck

 

[Anonymous Poster]

Furnace cement is a product that's been around for longer than I have. I've seen it on old coal furnaces, and I've used it on wood burners with fit up problems.
It does become brittle over time, and you don't want to buy a larger can than you are going to use, but it is great stuff when you need it.

 

[Chuck52]

I was at the auto parts store and found a product they sell for exhaust manifold repair. I bet it's the same thing as furnace cement, but in a smaller size for more bucks. It was maybe a 2 oz jar for $6.99, and I saw a pint of furnace cement for a few bucks. However, I'll probably buy the auto parts stuff when I get to FL because it may be easier to find there. I figure if I try to carry that stuff on the plane with me they'll lock me up. I'm not taking my pocket knife, which I always carry, or even finger nail clippers. It figures that I would be flying on a one way ticket to a city with a major military base on the first day of the increased airport security measures.

Chuck