Temp Gauge not responding

[Kidd7]

I noticed last night that the temp gauge wasn't moving, sat at C for 1/2 hour drive or so. Definitely enough time to come up to operating temp. It blew warm air through the vents. I flushed the coolant last week. This morning I checked the level in the radiator and added some, it was an inch or so low. I data logged it today for a short drive and it looks like the ECU is reporting the temp correctly.
Are there 2 different temp sensors? One for the ECU and another for the gauges? Or does the signal split from 1 sensors to feed both? Any ideas on whats wrong here? Thanks.

 

[koda2000]

2 different devices. A sensor for the ECU and a sender for the gauge. What engine? V8 gauge sender has one wire (easy to ID). if you ground it the gauge should go to full HOT. V6 SOHC engine is harder to ID. The sender and sensor are right next to each other on top of the t-stat housing and they both have two wires due to the plastic housing. The SOHC t-stat housing also tend to leak once you try to replace either device, because the brass inserts break free of the plastic. Later models used a push-in sensor/sender design that seal with an O-ring.

 

[danno2944]

Out of curiosity what were you average running IAC temps?

There is two sensors, one that goes to PCM and one to your gauge. Sounds like the one to your gauge is bad.

You can test them, but the problem is the cheap/poor design of the sensors in the thermostat housing. They are prone to cracking or just spinning the brass connections to plastic housing which can cause leaks and much more expensive and difficult repair.

My advice if you really want to monitor is great an aftermarket temp gauge and an inline temp sensor adaptor that fits right in your coolant hoses.

 

[Kidd7]

It's the 5.0, forgot to add that. I could probably use an adapter like that with a factory sender and still use the original gauge. I'll figure something out. Thanks for the heads up on removing the old, I would have found that out the hard way.

 

[koda2000]

It's the 5.0, forgot to add that. I could probably use an adapter like that with a factory sender and still use the original gauge. I'll figure something out. Thanks for the heads up on removing the old, I would have found that out the hard way.

The 5.0L temp sender is easy to change. It just screws into the metal intake. No plastic to worry about. I don't know what you mean by using an adapter. You just need to go to the auto parts store and by a temp SENDER.

What temp did you determine your coolant was reaching? It should be around 190+ degrees. If you're closer to 160, or less, there's nothing wrong with your temp sender. You would need a new thermostat, because it's stuck open. I had this happen on one of our Mountaineers, which was getting horrible fuel economy. Eventually the CEL came on with a TDC of P0125. The factory temp gauge only works w/in a narrow temp, and then should always register in the middle between hot and cold (unless you're overheating).

 

[Kidd7]

Yup. I'm pretty sure it's stuck open. After drive today and watching the temp it peaked at about 175, never more than that.I'm adding a T stat to the list.
And I was referencing danno2944's post about the brass fitting breaking and causing leaks.

 

[danno2944]

Not sure if you caught that Kidd7, but the 5.0l has a metal housing, So not to worry about plastic, even though it sounds like the sender is working fine.

 

[koda2000]

Tip: Don't forget to get the t-stat housing gasket too. The night before you install the new t-stat, place it in the housing (pointy part out, rattler near the top) and glue the gasket in place behind the t-stat. That makes installing the housing much easier. Also, you might also want to replace the bypass hose while your in there.

 

[Kidd7]

Thanks for the followup danno2944 I haven't gotten in there to look over the sender, I remember seeing it when I flushed the coolant last week, but not any details about it. I'll start with the T stat when I do the tune up and go from there.

 

[danno2944]

Would you recommend the bypass for the 4.0sohc as I am about to tackle this job as well?

 

[koda2000]

Would you recommend the bypass for the 4.0sohc as I am about to tackle this job as well?

IIRC the SOHC bypass hose is not part of the top half of the t-stat housing. I think it comes off the bottom part and goes to the the water pump. I recall that when I replaced the W/P on our '97 the first W/P I bought didn't have the bung for the bypass hose and I ended up returning it to Advance and bought one at NAPA, which had the bypass bung (it cost me double).

As far as replacing the bypass hose in general... In my experience it's typically the first hose to blow for some reason.