P0125 and trans line question

[koda2000]

2000 Mountaineer, 5.0, AWD, 151K

#1. i think i know the answer to this one but...

i have a CEL and a temp gauge that doesn't seem to move at all. scanned for codes and got "P0125 coolant temp insufficient for closed loop operation".

i was ready to put in another temp sender, as i tested the gauge and wire by grounding the wire and the gauge went to full HIGH. i get heat and it's pretty warm (of course it's 47 degrees out, not exactly the great white north in GA) so i was a little surprised that it appears to be the thermostat.
so, is the temp gauge like the oil pressure gauge in that it will only register if the coolant reaches 190 degrees +? will failure to enter closed loop operation cause poor fuel mileage (because my fuel mileage sucks and the inside of my tail pipe is black & sooty)?

#2. my transmission lines are really incredibly rusty. i don't trust them. my questions are, does anyone (other than maybe Ford) offer pre-bent trans lines? do the lines screw into the transmission or are there some sort of stupid quick-disconnects like used on the fuel lines? what do you think about using rubber trans line on barbed fittings instead of metal lines? i know i can get straight universal line an bent it, but i've never had much luck bending line that thick and there are too many weird bends to make.

 

[albi1cnobi1]

2000 Mountaineer, 5.0, AWD, 151K

#1. i think i know the answer to this one but...

i have a CEL and a temp gauge that doesn't seem to move at all. scanned for codes and got "P0125 coolant temp insufficient for closed loop operation".

i was ready to put in another temp sender, as i tested the gauge and wire by grounding the wire and the gauge went to full HIGH. i get heat and it's pretty warm (of course it's 47 degrees out, not exactly the great white north in GA) so i was a little surprised that it appears to be the thermostat.
so, is the temp gauge like the oil pressure gauge in that it will only register if the coolant reaches 190 degrees +? will failure to enter closed loop operation cause poor fuel mileage (because my fuel mileage sucks and the inside of my tail pipe is black & sooty)?



#2. my transmission lines are really incredibly rusty. i don't trust them. my questions are, does anyone (other than maybe Ford) offer pre-bent trans lines? do the lines screw into the transmission or are there some sort of stupid quick-disconnects like used on the fuel lines? what do you think about using rubber trans line on barbed fittings instead of metal lines? i know i can get straight universal line an bent it, but i've never had much luck bending line that thick and there are too many weird bends to make.

#1 Yes and no. The gauge and the PCM are reading from different sensors. The gauge in the dash won't really start to climb until about 140*. And the PCM won't go into closed loop until about 160*(give or take a few *). And yes, running in open loop will kill your mileage. So it does sound like your t-stat is stuck open. If the stat is stuck open it doesn't let the engine reach operating temps. Sounds like you're probably running about 140* or so.


#2 If you don't want to go to the dealer(if they even have them) then you other choice is probably a tranny shop. If you take the old ones off I'm sure a good shop could match them up pretty inexpensively. And yes they screw into the tranny, but depending on which line the other end of one of the lines goes to the tranny cooler and that is just a flare with a hose clamp to rubber hose. The other one screws into the radiator.

 

[koda2000]

thanks for the suggestion re trying a transmission shop for the lines. i didn't think of that.

 

[koda2000]

Update:

P0125 -
I put in a new fail-safe thermostat today. No more CEL and temp gauge now works perfectlly, needle's right in the center of the gauge. I also noticed that the fuel mileage actual went up, on a test drive around the block, so operating in "closed loop mode" seems to be improving the MPG too.

Transmission Lines:
I tried going to my local trans shop, to ask about them making me some new metal lines - They went out of business! So I'll either have to try another out-of-town shop, or pop for OE style lines (looks like about $140-$150 w/shipping). I considered running rubber transmission line, but I think the bends/routing are too complex to allow that to work. :/

 

[albi1cnobi1]

Sweet! Glad that fixed it. Once you get those tranny lines figured out and you'll be golden.

 

[koda2000]

Sweet! Glad that fixed it. Once you get those tranny lines figured out and you'll be golden.

well, i'm getting there. also had the front wheels balanced, replaced a scarey worn out outer tie-rod end and both front sway-bar end links, changed all the filters and most of the fluids. still need to fix O/D switch, autolock and radio display, replace the lift-gate/rear window lock actuator and handle-to-rod clip and spend about 3 days cleaning the interior. then i'll call it done.