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Discussion Starter · #1 ·
Did a full engine rebuild on my 1996 5.2. Runs great, nice and quiet. I filled it up with antifreeze, fired it up and let it run until it burped, and burp it did. Temperature on dash rose and after the burp it went to what I usually see, a quarter ish to the left of the middle on gauge. Looks all well and dandy.

I checked with little plug in OBD2 scanner just to see what it was running at and its been around 210 degrees while on the road, idling, highway.. Sounds a little high right? Before I rebuilt it I remember it being around 180-190ish range. It's a 195 Thermostat. I checked the upper radiator hose, nice and hot, heat blows hot.

I used a Fluke temp gun and hose and thermostat housing is 178 or so. Engine block around the same. Dash gauge is happy, computer says 210.. What gives?
 

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Discussion Starter · #3 ·
I am positive you already did, but I will ask anyway, did you replace the temp sensor?
Ha, funny enough I did not replace it. It was working before the tear down, I reckoned it would have survived sitting on shelf for past 1 year and 3 months while truck was in a million pieces. It is "Working" since trucks not complaining about it. Just not showing right temps, or is it? I'll run to parts store and grab another one. Only takes literally 30 seconds to swap out since I don't have A/c.

Can't be that easy to fix this mystery..
 

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Sure, why not. It's relatively cheap & easy.
Anyone who does a full engine rebuild is way ahead of me, but I remember a four year old Taurus I bought quite a long time ago, and when I bought it it was always showing on the way cool side, even when I knew I had it running hot as a pistol. I got a garage to plug in to the computer for me, and it turned out the gauge was reading inaccurately, so I popped in a new sensor and the gauge came up to what the computer said.

So, worth a try anyway. And if that doesn't do it, I would THINK it to be theoretically possible that the PCM could be sending a bogus signal for the gauge? (Not quite as doable to be swapping out PCMs though.)

As I typed, you are way over my head so you may already know about this, but also there is a self-diagnostic check you can do on your cluster quite easily. If you don't have it, I will find it on this site & paste the link for it.
 

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Temperature on dash rose and after the burp it went to what I usually see, a quarter ish to the left of the middle on gauge. Looks all well and dandy.

I checked with little plug in OBD2 scanner just to see what it was running at and its been around 210 degrees while on the road, idling, highway..

I used a Fluke temp gun and hose and thermostat housing is 178 or so. Engine block around the same. Dash gauge is happy, computer says 210.. What gives?
. . . however, as I reread this and consider what I just typed, I guess the computer is saying one thing but what the computer is saying is not what the gauge is showing. Which would tend to make me THINK that the sensor is not at issue.

I am looking at some handwritten notes that I wrote from a post that Old Marine made, and the middle mark in the gauge is SUPPOSED to be ABOUT 190f. The first mark to the left (cooler side) is SUPPOSED to be ABOUT 130f. "Check gauges' should come on at 251f.

(And, I don't remember what year FSM he was using when he made that post, it may have been for an '03, and I don't know if that makes a difference on this. They are utilizing a different bus system, so it might.)

Hmmm, so without erasing what I typed, gauge is showing ABOUT what your fluke is, even though it is NOT showing what your PCM is putting out. That got confusing for me.

But you are right, what gives? I dunno, but even after rethinking all this, I'd still change out the sensor just for the helluvit and see what happens. . . .
 

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I just read a little blurb on a site that I don't really trust, but it is saying that at least some dodge dakota engines in '96 had two sensors, and one of them is the "engine coolant temp sensor" and the other is "the gauge coolant temp sensor." Is that correct for the 5.2?

Okay, so ON EDIT, if this from still another site is correct re your '96, it might explain it:

RE: 95 5.2 temp sensor


Message:
Which sensor did you replace? There are 2.

One that sends coolant tempt to pcm and one for the guage in the cab.

- Dan M
RE: 95 5.2 temp sensor


Message:
The sender next to the dizzy is the OIL PRESSURE sender.
The two temp senders are up front on the intake manifold



And this is different than the way it is for the '03, according to my '03 FSM and also different than the '97-'99 Dak Haynes shows it. But it must be the way that '95 Taurus I referred to was.
 

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Discussion Starter · #7 ·
I just read a little blurb on a site that I don't really trust, but it is saying that at least some dodge dakota engines in '96 had two sensors, and one of them is the "engine coolant temp sensor" and the other is "the gauge coolant temp sensor." Is that correct for the 5.2?

Okay, so ON EDIT, if this from still another site is correct re your '96, it might explain it:

RE: 95 5.2 temp sensor


Message:
Which sensor did you replace? There are 2.

One that sends coolant tempt to pcm and one for the guage in the cab.

- Dan M
RE: 95 5.2 temp sensor


Message:
The sender next to the dizzy is the OIL PRESSURE sender.
The two temp senders are up front on the intake manifold



And this is different than the way it is for the '03, according to my '03 FSM and also different than the '97-'99 Dak Haynes shows it. But it must be the way that '95 Taurus I referred to was.
Yup indeed there are two sensors. I just changed out the 2 pin one going to the computer and now its saying I'm running at 200..with a 195 thermostat and its 95 degrees currently here in Rhode Island so maybe that is correct.. I bought both sensors just in case I swap the 1 pin going to dash one. I'm contemplating plumbing an aftermarket temperature gauge somewhere just for comparison purposes.
 
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