coolant temp question

[MattPersman]

Hi I am a new owner of a 91 X Sport 4x4 blah blah. anyways doing some routine maintenance on the thing, one thing I noticed was the coolant gauge is always way low. Now it is cold here in Indiana like it got to 25 maybe today, but was 4 degrees when I went to work this morning, but anyways even this weekend when it was 37 the temp gauge didn't move a whole lot. I did a search and it seems to replace t-stat, coolant temp sensor, etc. I did the T-stat, added new coolant. No help there, didn't seem like the old one was bad when I took it out but who cares its under $10.

So I figure, I will go to the coolant temp sensor next. went to autozone and got one for $15. I put it in. its the one on the right top of the T-stat area with the 2 prong electrical plug, I popped that in. Let my truck idle for like 10 mins and took it for a quick 5 min drive top speed of like 55 mph and still reads low. Doing the search I noticed in a few threads about 2 sensors? I am guessing I replaced the one that gives info to the ECC (the computer as I think its called in Ford terms, was a GM man before this). Is there truely another one that sends the reading to the gauge? If so whats it called and what can I ask for at the autoparts store. I have access to most major midwest parts stores in driving range.

Anyways really the only thing I did not change was the radiator cap. I think I may swing by and get one after work tomorrow cause who knows maybe its bad? Never had one go out on all the vehicles I have owned so who knows. It says replace or test on top of the cap. Also I did not flush the radiator but it looked decent in there. Could the cap be my culprit, or maybe the "other" sensor?

I can only guess MPG is effected by the thing thinking and actually running this cool. I rather have it this way than overheating I suppose.

Thanks

 

[Msupertek]

Quick Way To See If Guage Is Operational

Go outside to your truck turn the key on and disconnect the coolant temp sender (one wire type sender near t-stat housing), and insert a piece of wire into the L connector and put the other side to ground. The guage should go all the way over from cold to hot, then disconnect it from ground and it should go all the way back down. This lets you know it is operational, it doesn't mean it is accurate. Sense the guages hardly ever fail when compared to its counter part the sender, I would replace the sender if it passes this little test. Good luck!

 

[MattPersman]

Thanks for the advice

I will check it tomorrow when its light again and a little warmer perhaps. So this is the other sensor towards the left of the T-stat housing?

 

[Msupertek]

FORD CERTIFIED TECHNICIAN

Yes. You are correct.

 

[StalkExplorer]

Hey I am having the EXACT problem with my 94 LTD... I did the test you are talking about except I used a 10kohm pot instead of a piece of wire and when you dial the pot around the gauge on the dash gauge moves fine, in my mind, the gauge is 100%.

When I measured resistance between the negative post on battery (Fluke digital meter), and output terminal on sending unit (single wire) it was real flakey i.e it jumped from 8 ohms to infinity to 5 k, etc... So I thought hey, problem solved, it was just a bad sensor (sending unit)...

So today I replaced the sending unit ($8) but my guage is still way to low (exeact same description of problem there IS deflection, but it barely makes it to the line on the normal scale like about 1/10 FSD)...

The only thing I could think of was that there is a bad ground connection since it only has 1 wire for the output... I tested resistance between the negative post on the battery and the brass housing of the sending unit and it is about 1.3 ohms, and stable. Not too bad I thought considering its steel -> aluminum -> brass , but it still ain't workin...

Now it comes to the CEL (Code 116)... My CEL comes on and the ScanTool reports code 116 - ECT Sensor outside normal range. So I thought I'd replace the ECT anyway, it's only $25. No change. Still get code 116 and I still have minimal gauge deflection...

I swear these problems are somehow related, but I can't figure it out. Worse yet, the sensor (2 wire connection) has the ground and signal together, so a bad ground on the Engine wouldn't matter right?

I am going to hunt down the Engine and Chassis ground connections when it warms up a little to see if I can find a rusty connection or a rotten/melted wire someplace.

Arghhh.

 

[StalkExplorer]

Doh, it would appear that the two problems are definatly related. Replace the thermostat. Code 116 is fixed and then temp gauge rides between the "O" and "R" in normal... I guess I was just making things to complicated... I knew should have trusted those experienced X dudes... (i.e. refer to multiple threads on thermstat problems...)

 

[PicoG4]

do u have a link to that other thread?

 

[StalkExplorer]

I don't know how to link threads, but if you do a search, using the search feature and "all forums" for "Temperature Gauge" and/or "Temp Gauge" you should come across a couple of common problems.
More interesting searches "Code 116" and, hehe "Burping" - but it doesn't even have anything to do with beer?

Before you make the problem to complex (like me, hahaha) you should check:

1. Fluid levels
2. Rad cap
3. Leaks in hoses

1. Cycling temperature gauge - would appear to be a thermostat problem i.e one guy says the thermostat was for a lower temperature than stock (189F I think), so it cycled up and down. Another problem was not having the little "valve" thing at the 12:00 position to let air out. (There is a little hole (1/8") in the thermostat flange that should be positioned at the 12:00 position to ensure air is self-bled out of the system) Also suggested to, er, "burp" the cooling system (an effort to remove air).

2. No gauge defelction/running way to cold... This was my problem. The guage barely (doesn't even make it to the semi-circle under the word "Normal") have any deflection. Of course being the end of winter in Winnipeg, and with a continuous operation fan I guess the X cools real good.

3. Overheating - If the X is overheated, check the upper rad hose to see if it is real damn hot. If it isn't, your thermostat is probably stuck shut. Of course this would happen if you had no coolant, or no fan, etc...

4. Code 116 - This is the computers code for "ECT Temperature sensor out of self test range". Sounded like a wiring problem to me, but it is apparently the computer noticing the lack of the engines ability to get to operating temperature.

I'm sure there is more problems listed, but these seemed to be the common ones I came across, and the ones that helped me out...

My truck is running minty now, so if you want me to take measurements, etc to compare to yours let me know! And I have a ScanTool which gives all kinds of scary detailed information...

Good luck, and I hope this helps you out!