So I had a muffler shop reweld my exhaust where it broke the tack weld away from the mount under center of Jeep. In doing so, he showed me a small leak at the top where the manifold meets the motor-driver side. Said the manifold needs to be replaced eventually.

He said the pipe appears blue where the crack is on manifold at the motor which he said means too much heat. Said that can be running to lean (or rich - dont remember which), or could be a bad O2 sensor, etc.

Said if I have the manifold replaced without finding the root cause (of the blue pipe) then the same thing will happen.
Anyone heard of this? I'm not a mechanical guy but he seemed honest. Said dont pay me to replace the manifold until I address the heat problem. Wouldnt a bad O2 sensor etc set off codes?

Any input would be appreciated. Not sure if I should go to a general mechanic before the muffler guy replaces manifold.

Thanks

 

The O2 system is well monitored for the proper fuel/air ratio. If it falls outside the acceptable parameters, you'll get a code.

The manifold cracks people see on their 3.8L JKs are most likely caused by mechanical stress, in addition to normal manifold temperatures.

Are you the original owner of your 2009 JK? If so, the manifold is covered by the lifetime powertrain warranty.

 

thanks for the input. Im the second owner and just turned 91k miles.. would you recommend just having manifold replaced at muffler shop or taking to general mechanic to chase the cause of the mysterious blue tint on the pipe?

 

If the manifold is cracked, have it replaced by your mechanic of choice.
The blue you see may be from the hot exhaust gas escaping through the crack. Heat will be concentrated there.

 

thanks!

 

I second this. 3.8s have a tendency to crack manifolds, especially on the left. It helps to remove the factory wheel well liner or install a set of aftermarket vented liners to get some airflow in there. Heat extractor hoods, while expensive, also help cool the underwood temps. Everything is really packed into that engine bay and things get really hot.