So for the past few weeks I have been watching my ECT and EOT do some strange stuff. On some occasions while driving the EOT will suddenly drop 10 -15 degrees below the EOT. example: 202 ECT and 190 EOT. it has done it on the interstae and city driving.

It has happened with the ECT also. EOT will read normal then the the ect will drop 10-20 degrees, city and interstate.

The temperature that has dropped will fluctuate up and down then suddenly go back to its normal reading. Only 1 of the 2 will go out of whack at a time.

I have checked the wiring and found no obvious signs of fraying or wear. Thought about just replacing both sensors but I don't want to just throw money at it.

04 f250 CCSB 4x4 auto, 198,xxx miles, In the past 2 years the truck has had an EGR cooler delete, ford oil cooler, ford head gaskets and ARP studs. new ficm with Atlas 40 tune, blue spring upgrade, 200 degree t-stat, all filters are motorcraft, and using rottela T6. Have an SCTx4 with tunes from Gearhead.

 

Keep your eye one it, The sensors are known for not being the most accurate. When you changed the oil cooler you put the newer updated one in? 04 was the bad year for the factory oil cooler, they corrected it in 06, but you have to specify you want the updated one. Someone could have seen the early year and given you one that was on the shelf from 04. You can easily see the difference between the 2 the earlier one had small passages in the coolant while the upgraded had much wider openings for better flow of coolant. I would recommend a Diesel Site coolant filter no matter what, they left a lot of casting sand in the block and heads and it causes all kinds of trouble, when I added mine I didn't get a month before the filter was plugged solid. Now the filter has been on since september and still have good flow.

 

OIL cooler came from Autonation White Bear ford. Not sure if it was an updated one or not.

 

I have a similar problem. If I touch the wires into the sensors it comes back to normal.

I blame the pigtail.

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I have checked them( wiggled really) and it seemed hit or miss if it did anything for a short time.

 

Not much you can really do but watch them. KOEO they should read really close after a 12 hour cold soak. You can cross reference them with MAT, TFT, IAT, IAT2. You can also switch them around to see if it makes any difference since they're identical sensors. AFAIK, you can't get the pigtails for them unless it's on a complete harness, unless Alliant has them.

That is really weird though.

 

KOEO test they are within 1-2 degrees. Its crazy.

 

I have found some pigtails. When I get a chance to tear into the wiring I will see if they need to be replaced.

 

Did you order/buy them new or ??? looking for a part number as mine do the same thing... sometimes show a 10* difference, wiggle and back to normal.

 

First thing to check when dealing with intermittent electrical problems is ground connections.