[dlsayremn]

Any idea about what would cause this. Feedback Sensor casing melted. It was not touching anything hot where it melted. Don't think short inside would cause this much heat.

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[Action]

Was there a third port that melted off?

Action

 

[dlsayremn]

There was no third port. Probably should have posted a picture of the other side.
The other side.

This is how it looks new.

New one mounted in engine compartment

 

[Action]

Thanks for the added pictures.

I have seen melted EGR Feedback sensors. Just not recently and not on a 4.0l.
Those were due to an exhaust leak.
The insulated pipe in the last picture is EGR line correct?

Have no idea the cause of the melting. Seems like nothing is close by to cause that.

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[dlsayremn]

Action,
Correct, that is the EGR line.

Think I found the answer. Bought new high temp hoses for the DPRE sensor because I couldn't find the high side hose. Apparently, someone had replaced the high side hose with plastic gas line tubing that melted and let hot gas spew on the sensor. They had pulled the plastic tubing off before I got there.

If the new line blows, could indicate a serious, costly problem.
On-line search shows that the usual problem is high back pressure caused by a clogged cat or muffler that creates excess heat and pressure in the egr line.

 

[Action]

Yeah I have seen exhaust gases leak out and cause that issue.
The flex hoses that are replaced have to be hi temp.

It is very easy to check for restricted exhaust system which includes the cats.
Install vacuum gauge on the engine
Strat up the engine and wait until it is warmed up.
Once warmed on curb idle observe the vacuum gauge
What ever reading it has that reading should remain steady. IF the reading slowly drops to a lower level the exhaust system is restricted and not allowing all the exhaust gases to flow out

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[TBIRD430]

Correct. HAS to use that special high heat tubing!! Also, where does that sensor bolt up on your 4.0L? Hoses seem short to me here???

 

[dlsayremn]

TBIRD430,
The sensor doesn't bolt anywhere on the engine or elsewhere. It just sits on top of the hoses.