I am a new JK owner and I've found that when I put some pressure on the engine (like racing for a while or shifting at high rpm) the exhaust manifold becomes RED hot, went to the dealership and they told I need to change the o2 sensors, so I did that but it didn't fix the problem, after that they told me that one side of the header manifold is damaged and the gasket on the other side is blown, a thousand dollars later and I still have the problem so if anyone could help me out it would be highly appreciated........ THANKS

 

Glowing red exhaust manifolds are usually caused by a fuel/air mixture that is too rich. The excess fuel continues to burn after the power stroke of the piston, and is released into the exhaust manifold by the exhaust valve.

This can cause problems such as cracked exhaust manifold, blown gaskets, and eventually even burnt exhaust valves and seats ($$$).

Sounds like the dealership assumed that the O2 sensors were reporting a lean condition to the computer, and that would cause the injectors to add more fuel to the engine.

You didn't mention if you had tuned your engine with a aftermarket tuning chip. If so, then go back to your factory tune-up and see if that makes the problem go away. If your not the first owner, then possibly someone else has tuned the engine.

If the tune up is factory, then you need to determine what is causing the additional fuel. It could be a problem with the harness that goes to the O2 sensors. The sensors send a signal of zero to one volt DC. The computer sees zero volts as lean, and one volt as rich. If the signal wire has become shorted, then it will appear to the computer as the engine is always lean. You should get a code or check engine light with this condition. The computer could also be at fault, or several other sensors. Sounds like it needs to be put on a analyzer and have all the sensor readings checked for accuracy.

Good luck, these types of problems can be very difficult and expensive to find and fix.

 

Yes a rich situation can cause the manifolds to glow, but I highly doubt that there is to much of a problem other than your driving style these little engines aren't not your high reving sport bike engines. The cast iron manifold is a great insulator for heat, if you run this engine at higher rpm's for a extended amount of time the exhaust gas temp will climb into the 1300-1400F range, that is more than enough to make it glow. As for the manifold and gasket problem that is fairly common. If you are really concerned find a shop with a wide band O2 sensor and have them measure your Air/fuel ratio normal driving will be around 13.5-14.8 a/f ratio, when your pushing it a naturally aspirated motor will run around 12-13 a/f ratio at peak torque ( running hard ).

 

I'm not disputing what you guys have said about too rich causing a hot exhaust, but in my personal experience, just the opposite has been true.

Rich cools the valves and exhaust; too lean burns the exhaust valves and makes the manifold glow.

 

I have to agree with this. A high reving engine goes towards lean. If you are going to run a high rpms on a regular basis then go to the next higher octane and that will richen it up and that should fix it or you might have to get the highest octane pump gas.

 

I have to agree here. It has been my experience that a lean condition will cause higher exhaust temps.

To the OP- when you say racing for awhile, what are we talking here? A little zipping around town or back to back wide open throttle runs for an extended amount of time? And, when you notice the "glow" of the exhaust, is it at night? I have seen headers glow a little or turn pale orange at night that otherwise couldn't be seen in the daylight. I would be willing to bet that I could take almost any vehicle off a lot and run the dog snot out of it for an extended period of time and you would see the headers/manifolds glow a little if it were dark.

 

first of all thanx for responding, I found out today that it glows on wide open throttle even if the car is stopped and I rev the engine a couple of times. I mean it doesn't have to run for an extended amount of time if I just floor it down the street which is about 500 yards it would glow.

 

Had the cat. converter go bad on a friend's car, the manifolds would start to glow orange. Just something think about.

 

Just a question, how do you know your manifolds are glowing; do you not have the heat shields fitted over them (see pic). Or do you have aftermarket headers (which will get very hot)?

If you do still have the heat shields and these are glowing then yeah Huston, we have a problem.

 

My experience with racing engines is that a lean condition in the injector would burn up the pistons, and a rich conditio9n, which could be seen because of the prominent flames would cause the headers to glow, becuase the fuel was still burning outside the combustion chamber.