Background first... I have a 88" all orig. with 96K miles.
I HAD a code 42 & 43 which has sense been fixed with new injectors and Knock sensor. While working on that I also chased down a coolant leak with new water pump. New seals, gaskets, thermostat, plugs, wires, EGR valve... basically everything that was under the plenum.
Car was back together and test drove. After about 10 miles I got a SES, and when checked was a code 44. Cleared code and drove again, and after approx. 10 miles same thing... SES and code 44.
The coolant temp stayed within range at 195 degrees, the car ran fine except seem to idle slow when setting at a light.

The code 44 44 shows multiple thing to look at... one was O2 sensor which I replaced , and also replaced the coolant temp sensor under the throttle Body. I had trouble getting it to take coolant. I've been told that I need to burp the system, which requires running the engine with the cap off.

Problem... If I leave the cap off the coolant backs up and overflows out of the radiator fill. If I leave the cap on and run the engine for just a few minutes, my digital temp gauge will quickly climb to 230 and I shut the car off. The thermostat never opens, the radiator never gets warm???

Could a bad (Brand new) coolant temp sensor cause this? How would I test the sensor using a multi meter?

 

OK, you have a couple of problems here. You need to get the cooling system squared away so you can run the engine without overheating. Yes, getting it to "burp" and get all the air out can be a pain. Some will park on a slight incline or jack the front of the car a little bit so the air flows to the radiator easier. You can try not filling the rad. all the way and run it till the thermostat opens and coolant flows-then fill it. I've also run it some with the cap on and drive a little, let it cool and fill again. Just went through all that took me a couple of go rounds to get it fully air-free.

The sensor on the front of the engine sends temperature to the ECM not the gauge. If it is bad it will give you a code 14 or 15. The sensor for the gauge is on the passenger side towards the back of the head.

Code 44 is a lean condition, low voltage on that circuit. It comes on if the voltage is less that .2 volts on circuit 412 a purple wire, in closed loop. You already replaced the O2 sensor so you are getting low voltage by a bad connection, vacuum leak, EGR not working (I know you replaced the valve) or possibly a MAF problem. I'd check to make sure all the connections are good first including at the ECM.

Hope this helps!

 

I use a Lisle Spill free funnel to burp the system. Allows the coolant to expand and the air to escape.

Allow the engine to get to 200F then shut it off and let it cool. 2 or 3 cycles of that and it's good.

Don't let it get too hot or it will expand and overflow.

 

Or you could have drilled a couple 1/8 holes in thermostat flange and avoided all these gyrations.

 

The code 44 came AFTER the fuel injector and water pump replacement. That cured my code 42 & 43. I then refilled coolant and drove several times. The temp gauge seem to fluctuate between 195 and 185, but I figured that was because the thermostat was opening at 195 as it is suppose to and closed at 185. But I never seen it do that before. Normally just stayed at 195.
BUT after driving for about 10 miles I then got the SES and code 44.
THAT is when I replaced the coolant temp sensor and O2 sensor. AND THAT is when I started having the problem getting the coolant back in.

I have the front end elevated, and have tried to run it with the cap off, but it pushes coolant out. As it idle the coolant level rises in the tank.
With the cap on, my temp gauge goes to 230 degrees within only a few minutes (4 or 5) and thats where I shut it off. BUT the engine doesn't seem hot???

 

When I start the engine, the on dash temp gauge climbs to 230 within a few minutes, so I shut it off. BUT the engine does not feel hot. So I can't get the thermostat to open.

 

I think I will try that, thanks

 

Update: I rechecked for codes and got none. So if there is a bad sensor it isn't throwing a code. But I still can't run the car for more than a few minutes before the temp guage show 230, at which point I shut it off.

SO... I pulled of the throttle body, EGR sensor, Coolant temp sensor, upper radiator hose and thermostat. I didn't get any coolant spillage anywhere.
I tested the thermostat in boiling water and it opens fine.
I also tested the coolant temp sensor in a pot of water on the stove. With multi meter attached and set at 20k ohms it checked 3.90 at room temp and dropped to .19 at boiling.

Question, could a vacuum leak affect my digital dash temp gauge?

 

What's the oil temp when water is 230? Or the other way around, not sure which temp you mean by "230".

 

Good question, I did not think to check that. Thats just a flick of a switch on the dash to get that temp. If that gauge is working properly.
Thanks
The 230 temp is what my dash digital temp gauge climbs to. And it does that from stone cold (garage was 25 degrees) to 230 in about 5 minutes. I'm thinking it's giving me a false reading, but I don't know how to verify.
I don't have a infrared thermometer yet, but if I did... where would I take a reading.

 

Have you checked your airflow between the AC condenser and your radiator? Poor airflow will make for car over heat fast rendering all your testing mute.

BTW... just go but a new coolant sensor. They are 15 bucks and your car will thank you.

Consider...

 

As I stated earlier, I pulled the BRAND NEW coolant temp sensor and checked it with a multi meter on my stove while heating water to a boil, and it works fine. Also tested the thermostat and it works fine.

The birds nest in your picture would explain a car running hot, BUT the engine is cold, only the gauge shows hot.

I've drilled the small holes in the thermostat and have everything back together along with a new Idle Air Control in the throttle body.
When filling with coolant, it appears that when I removed the thermostat for testing, it may have burped the engine. I was able to get a lot more coolant in it this time. Way more than I lost when I removed it. Hopefully that was the burp it needed.
I will try starting it tomorrow and see if I made any headway.

 

You keep using those words, I donna it means what you think it means.

"Dash digital temp gauge": Is that coolant temperature or oil temperature? I wouldn't think oil, but one never knows without asking.

If coolant, touch the top radiator hose. Any warmth at all? Really, after 5 minutes idle, from cold, I wouldn't expect more than 130 on the gauge and a cool hose.

Hope the burp fixed it, could be your water pump was full of air, though I doubt it.

 

Ultimately, I can what the ECM sees so my thought would be to compare it to the ECM data. I usually check the ECM and hit the sensor with the IR thermometer. Say the base or the fat part of the sensor will be fine. Cold, see scanner and hit the sensor. Middle, repeat. Top, repeat. See what gives.

 

You can test it in a pan of hot water, you'll need a digital volt meter (set to ohms),a couple jumper leads, and a thermometer to measure the water temp. It will read close to room temp too if left out in a room.

 

This may not be related to your current problem, but billschroeder5842 showed a photo of a common problem with cooling on C4's. I have a similar problem: temps running to 220-230+, fans are running, it wouldn't cool down. After a close inspection, I discovered the radiator side for the primary fan (driver's side) was completely clogged with leaves and debris. (Some have referred this as as the "Hoover effect" for fall leaves.) After doing some VERY delicate cleaning with an airhose [VERY low pressure] and a toothbrush on a stick [GENTLY], no more high temp problems at all. I believe the first fan comes on about 205, and the second about 230?.

Plastic bags have also been known to get sucked up against the radiator (between the AC condenser and the radiator), so check for that too.