[FIXED] 2004 Ford Escape 3.0 V6 melted DPFE sensor

My daughter called tonight when her Escape started making a hissing sound on the way home. She pulled off the road checked gauges, for leaks, etc. before calling and reported no lose of power so I told her to go ahead and drive it home. It was dark when she got home but we found the DPFE sensor was melted.

My first thought was excessive back pressure from a plugged cat, but I would have thought a cat that was plugged that bad would have caused drivability problems. A bit of searching the net and I found some folks had the DPFE sensor melt due to plugged cats and there was a mention that there was a known problem with the Ford DPFE sensors.

Questions: Is there known issues with the Ford OEM sensors? Since the DPFE ports are so covenant would there be any issue measuring back pressure there?

Did some more searching and found that the two high temp silicone hoses that connect the sensor to the DPFE ports can crack causing exhaust flow over the sensor which melts it.

JeffBirt wrote: Did some more searching and found that the two high temp silicone hoses that connect the sensor to the DPFE ports can crack causing exhaust flow over the sensor which melts it.

I have heard of clogged cats causing this, but like you said, there's no lack of performance. Fingers crossed!

As far as measuring back pressure at that point, yes!
There are a couple Scanner Danner videos where he does just that.

I've seen the OE and aftermarket sensors burn on these, and it's always been due to a restricted catalyst.

That video Noah posted is perfect. If you don't have any excessive backpressure, then I say you're good to replace the sensor and the hoses for good measure. I've used the Dorman versions of both with no problems.

Thanks for confirming that. I realize it will only measure the cat on that bank and the downstream cat but it will let me know if there is excessive back pressure that blow the sensor loose. Considering it more I would think that if the hoses were good, even with just a press fit connection it would take 5-10 PSI to pop a hose loose and with that much backpressure there would certainly be driveability issues. The parts stores open up here in a few minutes so I will call around and try to find the sensor.

The upstream cats are built into the exhaust manifolds on this vehicle and each one of them is more than $500!!! The downstream is cheap by comparison at about $200.

We found 9-10 PSI from the DPFE port. An old O2 sensor and some redneck engineering and we had a bung to screw in an O2 port. The reading downstream O2 sensor was 5-6 PSI but I did not have a great seal. I'm thinking that finding that much back pressure on the downstream side of one bank points to the cat #3 the downstream cat. There are no O2 sensors on it though so I guess the option is to unbolt it and see if that changes the backpressure reading.

This vehicle has two mufflers (or resonator and muffler if you prefer), has anyone ever seen on of those collapse and cause a backpressure problem?

Thanks for your help.

Further update:

We pulled the rear downstream O2 sensor and got 5-6 PSI, or the same as the front downstream. This seems to point to the downstream cat (#3 cat). I tired to break loose the nuts on the front coupling of the #3 cat and not only do they not want to budge but they seem to be neither SAE or metric: 9/16" is too small, 5/8" is way to large, 14mm is too small and 15mm is a bit too large. As it is 30F out today we are working on it a bit at a time. It is supposed to be a whopping 40F tomorrow so maybe I can bet them broken loose then. I used to have a nut breaker but have not seen it in years so it might be new tool buying time

Aw man, I'm sorry you found a backpressure issue. I was honestly hoping it'd just be a failed hose.

Now that you're doing after the downstream cat, I gotta tell ya, it's usually because an upstream cat fell apart and plugged the downstream. Keep your eyes open for bits of substrate. The front upstream cat (radiator side) is pretty easy to replace, but the rear one takes more work.

Gotta love rusted exhaust nuts! :lol: Here's hoping the rest of the job goes smoothly for ya.

With some persuasion from the hot wrench and vice grips I got the nuts off the front coupler for the 3rd cat. I was able to peer inside with a flashlight and mirror and saw no chunks at the inset and the honeycomb/grid looked OK, just a white color to most of it (don't know if that color is normal or not). I put the pressure gauge back on the DPFE port and got nearly 0 PSI, just a bit of bouncing as the engine wanted to surge at 3,500 RPM.

I guess the question now is: Is the problem in the 3rd cat or the resonator or muffler? The rear of the 3rd cat just has a typical muffler 'U' clamp so it should b easyish to undo and free the rear of the 3rd cat, connect the front of it and try another measurement. If I had a lift and was working inside it would likely be easier and quicker just to drill a small hole for a pressure measurement and then just weld the hole up.

Wow, color me surprised! :ohmy: I fully expected you to find chunks of substrate falling out of the 3rd cat... I've never seen a resonator or muffler plug before, but there's a first time for everything.

I think you're on the right track with removing the downstream cat from the rest of the exhaust and rechecking your backpressure reading. I found a parts diagram that seems correct for your Escape, if I remember right:



Looks like the last place to test would be at the flange between the resonator and muffler. More rusty bolts.

It was the downstream cat. Pulled the resonator off of it and hooked the cat back up and the backpressure was back. Parts ordered from Rock Auto same brands as O'Reilly had, but 1/3 less cost and both parts are stainless too. All together she has about $300 in parts and a few days without her car, not too bad. Of course Dad works for free

JeffBirt wrote: It was the downstream cat. Pulled the resonator off of it and hooked the cat back up and the backpressure was back. Parts ordered from Rock Auto same brands as O'Reilly had, but 1/3 less cost and both parts are stainless too. All together she has about $300 in parts and a few days without her car, not too bad. Of course Dad works for free

Well that's not too bad, then! Just be sure to remind her how awesome you are for doing all this free work. :lol:

Let us know how it turns out when everything goes backtogether? Also, big thumbs up for Rock Auto, love that place.

Popped the rear cat and resonator in and checked the backpressure again and it was a big fat ZERO! Then we installed the new DPFE sensor and took a test drive. The only hiccup was Rock Auto not putting the two exhaust gaskets in the box so I had to get them locally.

I was thinking about the back pressure testing this morning. I think if I were to do it again I would drill a small hole in the exhaust tubing (on the side) and then plug it with a screw. My vacuum/pressure gauge cam with several small cone shaped tips so a large hole would not be required. The screw would seal it well enough and when it rusted it would be sealed permanently. If you wanted you could put some of that exhaust gasket paste on the screw. This would work if you don't have a welder or don't want to take the time to drag it out and hook it up for a 5 minute job. (I have a lot of crap in my little single car garage.)

Sweet! I'm slapping a [FIXED] on this one. Did you happen to notice any improved performance? I'm still curious how the downstream cat failed... Maybe there's two separate substrates inside, one disintegrated and jammed into the other. :huh: Not that big a deal now, just thinking out loud.

I'm totally good with the screw reseal procedure, too. Probably would have saved some frustration with rusty nuts. But hey, at least it turned out that you had to get those loose anyway. :lol:

She says it runs much better, more power so she has had to modify her driving to compensate. She has only had this vehicle about 2 months and it was well cared for before. Looking in the front and rear of the cat I see no signs of damage, the matrix seems relatively open, it is a fine grid so the holes are not large to begin with and there is no rattling sound.

I tried to find some pictures of cats online as I have never had the need to swap one out before and wanted to know what they looked like inside. It seems some have 2-3 separate sections so perhaps the damage is between sections? I'm also curious as to why it failed as and why there was no CEL. The battery died on it a month or so ago and I had a scan tool on it at that time and there were no codes really other than that related to the battery being dead. I might just have to cut it apart and have a peek at the innards