96 Explorer 4.0 OHV temp gauge stuck on cold. HELP!

[Y2Caleb]

Last evening I took out the tstat, it was indeed stuck open. It was even tough to close with my hands! Cleaned up both mounting surfaces and installed another one (192 degrees).

The sealer has to cure for 24 hours, since it's so dang cold I'll probably wait until tomorrow to fill the coolant and take it for a spin.

 

[Jim_WY]

I'm having a similar problem on my 96 with the V6. For years, this vehicle's temp gauge went to the middle and stayed there, very steady. A few months ago, it started to be a bit erratic and didn't go as high as before. So I just put in a new thermostat.

Now, it doesn't go as high as it did before I changed it, and it's still a bit erratic. I have plenty of good, high temperature output from the heater, and it's been near freezing here. But the gauge just doesn't go as high as I'd like to see it go. I figure if it's accurate (such as it could be), then the engine is never really reaching the optimum operating temperature.

I guess I could swap the thermostat again. And I could try shorting the sending wire for the gauge to ground to see if it'll read full-scale, and check all of that wiring and the connector, etc.

I keep wondering if I might still have some air in the system, but it's been a few days, driving it a number of times since I swapped in the new thermostat.

I'd be curious to hear what the final outcome was for Y2Caleb.

Edit to add: I found this photo on another T-Stat thread. It shows EXACTLY what I'm seeing for the most part now. Seems too cold, and the gauge used to always read dead in the middle. Something has changed!

 

[Y2Caleb]

Pardon the delay in my response, wife smashed her car to SH*T and it's been crazy looking for another ride while sharing the mountaineer.

Anyway, I put in the new tstat and the temp gauge was still at C. Just like you I had good heat thankfully. I ended up replacing two sensors. I believe they were the coolant temp sensor and coolant temp sender. I have a V8, but I'd be happy to snap a photo of each if it'll be of any help.

 

[Themightyquinn]

Can someone post a picture of the temp sensor for the ECU? I have the 4.0L OHV in my 96 limited. I have heard different things on different posts. One said it was in front of the ignition coil pack and another said it was on the driver side block. Also I tried grounding out the sending unit and I wanted to know if I did it right. I had the key on engine off, set my multimeter to continuity setting, connected one lead to the black cable of the battery and the other to the plug for the sending unit. I heard the continuity ring which I thought was strange. My gauge did not rise. Was I doing this correctly? Does the engine have to be running during this. And why did I hear the ring for continuity? Also is there a way to test the sending unit alone, such as a resistance check?

 

[lobo411]

Can someone post a picture of the temp sensor for the ECU? I have the 4.0L OHV in my 96 limited. I have heard different things on different posts. One said it was in front of the ignition coil pack and another said it was on the driver side block. Also I tried grounding out the sending unit and I wanted to know if I did it right. I had the key on engine off, set my multimeter to continuity setting, connected one lead to the black cable of the battery and the other to the plug for the sending unit. I heard the continuity ring which I thought was strange. My gauge did not rise. Was I doing this correctly? Does the engine have to be running during this. And why did I hear the ring for continuity? Also is there a way to test the sending unit alone, such as a resistance check?

I don't have a pic, but it's the sensor with a single wire, threaded into the lower intake manifold just below where the upper radiator hose meets the thermostat housing/water outlet.

I didn't bother testing it. I replaced it a few weeks ago and it solved my lazy temp gauge issue. I think it was about $10. My attitude is at that price, it's cheaper to replace than to test.

 

[Themightyquinn]

Thanks Lobo. I found the temp sensor for the ecu. it is directly across from temp sender on the lower intake manifold. I will replace the sender tomorrow and cross my fingers.

 

[hafcanadian]

How to get at things?

So my 97 Limited SOHC 4.0 has the same symptoms, and I'm looking for the mentioned sensor. Just behind the thermostat housing, on top of the manifold, are two side by side fittings. One has an orange cap and one a gray. The orange one that's more to the passenger side has two wires, one looks like black with yellow stripe, the other red with white stripe. The gray fitting has one gray red-striped wire and one green wire. So neither has a single wire out its top. The gray fitting appears to be screw-in, and seems to have white Teflon tape at its base, probably a no-no if any ground was needed there.

The tape appears relatively clean compared to the rest of the engine compartment, so I presume the device was changed out or temporarily removed, likely when the thermostat was replaced a few years back at a dealership shop. It's been since then that the gauge doesn't rise high enough, so I suspect the Teflon tape is the culprit, not sure. The device, however, appears to be gray plastic, so how can I test with a ground jumper? Maybe scrape off some visible tape and try to get some semblance of metal contact for a jumper?

Bigger question is how does the large, many-compartmented air plenum on top of it all come off to get it out of my way? I only see 3 screws up front on top, and several things fasten to it... air and fuel controls I assume. I don't want to start taking things apart I may have trouble getting back, or knock dirt into a fuel or air opening.

I took photos, but apparently this site doesn't have a simple attachment feature, and I don't have them on a URL resource.

 

[Themightyquinn]

So I used actual wiring to ground the sender wire, and my temp gauge went as far up as it could go. So a multimeter does not double as a singe wire.
Canadian: the plenum you are talking about is the upper intake manifold. You can remove the temp sender without removing anything else. As for the temp sensor, you will have to remove the air intake tube and the throttle body. You do not need to remove the upper intake manifold which is the compartmental air plenum you are referring to. I am in the middle of a fuel injector service so right now I have the upper intake manifold, fuel rail, and injectors off.

 

[XLTrunner]

Because hafcanadian has the SOHC engine, the sensor-sender are on top of the thermostat housing located slightly under and to the right of the Upper Intake Manifold. The Sensor with the gray wiring connector can usually be unscrewed from the t-stat housing and replaced. The Sender with orange connector also threads into the t-stat housing. However, those almost never come out because the geniuses at Ford designed it so that the brass bushing it screws into is molded into the thermoplastic t-stat housing...and, when you try to unscrew it, the entire bushing breaks it's bond with the plastic housing and spins with the Sender. Result...a new t-stat housing is required. At least they come with new Sensor & Sender...but, more work is required to access and replace it.

You ask about removing the Upper Intake Manifold to access these. It's not a big deal...but, pay attention to where the various vacuum hoses and wiring connectors go. There are a total of 8 torx head screws (Torx #30 ) holding it on. Three in the front, two in the middle and three in the back. The two in the middle aren't visible...but, you'll notice an indent molded into the side of the air chambers. One is near the IAC valve (valve does not need to be removed) and one near the VIS ass'y. (that does not need to be removed, either). A 1/4" socket/extension will be required to get down between the sides of the air chamber and to the head of each of those two screws. Of course, there are several vacuum hoses, wire connectors and throttle cables (Throttle Body Does Not have to be removed) that have to come off...but, no big deal. Some on here say they have removed the t-stat housing without removing the Upper Intake Manifold. I did not see how that was going to be possible on my '98 SOHC. The Upper had to come off and either the Lower Intake Manifold or the alternator w/alternator cast mtg block had to come off to gain some slack in the smaller wiring harness that was draped snugly across the top of the t-stat housing so that it couldn't be lifted up off the engine. PM me if you want a play by play description on how to do this. Just did it on mine a few weeks ago after doing a rehearsal at the local Pick N Pull.

 

[hafcanadian]

XLTrunner, your description is spot-on what I have. I note some access might be afforded by removing just the large intake tube between the air filter and manifold, but taking the entire thing (upper intake) off looked like it would make working with the apparent problem fittings a darn sight easier. Thanks for describing how, and for the warning about staying away from the orange-capped device.

Thanks to both of you for your experienced input. My service advisor described a different procedure last year that I recall involved some other sensors or senders down deep and a lot of expensive labor. Hopefully he wasn't right. I thought they'd already replaced any around the thermostat housing without any change in the gauge. Some had suggested it was a problem with the gauge cluster.

Maybe I'll get to it this week and see if that gray-capped one is the culprit.

Is there an aftermarket service guide book you can recommend for use with this car? I used to get books for my vehicles decades ago, but since '97 both my Fords have just gone to the dealer for service... a lot more complex rigs since my '70 Shelby days. Chilton, Climer, Haynes, Glenn's are publishers I remember.

 

[XLTrunner]

I've pretty much given up on Haynes and Chiltons...too general. I think forums such as this one do more good than any manual. I like to hear from guys who have actually tackled a project in order to learn the ins and outs of each step of the process. Hate it when a manual says something like "remove Thermostat Housing" without going into detail as to what to expect along the way.

Like you...I cut my teeth working alongside my dad on 60's-early 70's cars. Still have a '67 Cougar XR7 in the garage to work on just to maintain my sanity from working around all these stupid sensors, onboard computers and electronic gadgets that everyone seems to be so enamored with. Beware when you go buy one of today's vehicles 6-8-10 years from now and discover it's going to cost upwards of $800-$1000 just to replace one of the HID or LED headlamp assemblies because you have to dismantle the entire front fascia of the car to get at them. But hey, they sure look cool....