200 is normal, the thermostat factory is 195. As a general rule. 200-210 is normal operating range. Raised eyebrows at 220. Start implementing cool down procedures at 230. Anything over 230 would be considered hot.

When you get your real gauge, you will get more real world numbers. And it will show the temp going over 230 sometimes after shutdown (if you get a mechanical gauge that reads all the time) but that is normal, as soon as you start it up and the water starts circulating it will cool down.

 

With the temperature at 200 where was the stock dash temp guage? If it went from cold to pegged hot then it's likely the sending unit is toast.
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Replace it and at 200 you should be reading straight up mid range.

Karl, the president of the SGADL, will be around soon with the testing procedures
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Please define "getting hot". Exactly what symptoms are you seeing? Steam venting from radiator cap? Engine knocking and running poorly? Gauge pegged high? Gauge showing higher than normal but not pegged? Not trying to bust your butt (I only do that to Dave), but a vague "getting hot" description tells us virtually nothing. You know what you're seeing but we sure don't.


As the others have already said, that is a perfectly thoroughly amazingly wonderfully normal physical temperature value.

Sure seems like an indication problem, unless there's some other unspecified physical observation for "getting hot". (Hint, hint...)

Where does the needle point when you measured 200F?

Where does the needle normally point when all seemed good? In other words, driving around with the AC off?


Nor should it. 200F is nowhere close enough to the point where the fan clutch will kick in. Don't waste your time replacing it just yet.

 

See how the guys above are saying "where is your gauge pointing?". When you get your other gauge, and the engine is at 200 degrees, the gauge pointer on the aftermarket gauge will point to 200. That's amazing isn't it? The factory temp, oil pressure and ammeter gauges are only good for a concourse restored truck. One that is driven daily I put aftermarket gauges on it.

 

Dave, Dave, Dave,

The first step is admitting you have a problem. When you're ready, and we all reach that point at our own pace, we have an accredited 12-step residential program here at the Stock Gauge Anti-Defamation League. Tastefully appointed rooms, beautiful grounds, a wholesome nutrition plan, and dedicated professional staff who only want the best for you. You'll be amongst friends here. You don't have to let the anger consume you anymore.

 

Karl, you're never going to get Dave into our program with public humiliation. You should PM him so he can find the error of his ways in a personal and private manner. I mean some guys are just uncomfortable with the guage pointing at an O or an R. They need that reassurance of the needle pointing at a number. Not everyone is alphanumeric you know.

Dave's numeric guage will still be relying on a sending unit and wiring to the guage and then the guage needs to read that electronic signal and then decide where to point the dang needle.

To the OP, now that you have the laser pointer which can give numeric assurance to your guage's needle pointing you can save some money on guages, but you might need to replace your sending unit if it's pegged on H.

Let's us know how you'll proceed. Karl can help you diagnose your sending unit issue. And remember the SGADL is here to lend support and guidance. Whether it's a bad sending unit or a loose wire we have the solutions for you.

 

What if we just kidnap him? Might be less work.

 

I am cheap, I use the cheaper gauges from the local stores that are purely mechanical, no wiring required except for the dial illumination. It's nice to turn the key off and the gauge keeps on reading with no power. I have had problems once in awhile with them failing after about 5 or 6 years, but it's easy enough to buy another one and install it, and I have had a few that are still going.

 

Ok, This morning I swapped out the clutch fan for another new one and the one I took off was under warranty. Soon as I started the truck the fan had that sound we all love to hear when it is working. I did not put a different gauge on it so sorry Dave. I waited until the heat of the day to go for a test drive. I went on a 50 mile round trip test drive so if it was going to over heat it would have way before this with the old fan on. I took the two picture as soon as I got home and open the hood with it still running. So the bad new clutch fan was the problem. I want to thank all of you for your help. You too Dave

 

Mechanical guages have their issues too with probes, installation, bourdon tubes can leak. Like you said 4 or 5 years to failure.

My stock guage has been reading temperature properly without doing more than cleaning the connection at the sending unit for 36 years and 400k miles. Purrfect!

I can read my guage with the engine off and key in the on position. In my diesel that's handy when I've been parked for several hours I can see the engine temperature and then use the appropriate amount of time on my manual glow plug switch.

 

1949, looks like you got it dialed in! When your guage is pointing to the A you are A-OK!

 

I dont like the needle being that high, between the R & M is where I like it.
You may want to replace the sender to see if it will drop the needle.

To throw sand in your face my 300 needle runs just to the left of N on the cold line.
If I sit for say 15 min with the AC on and it is in the mid 90's it will climb a little just below the middle of the gauge.
But once I start moving it will drop right back down.
I need to check the wire connection if clean & tight, the sender is new.
Dave ----

 

Well yeah, check your connections for sure. If loose you will read a little cooler. Mine on the 6.9 diesel points straight up tween the R and the M. But I have seen it head up to the A when pulling a grade on a hot day. I'd say that running the AC on a hot day that hitting the A is probably not out of the normal range. But he did measure the temperature at 190 so it does seem like his guage reads high perhaps. But calibrated now so he should be able to get good info from his guage. He also knows where 200 sits as well. Adequate cockpit info, no?

 

Dave, You are right. It wouldn't hurt for me to change the sending unit. It is the original one. But I now know that when it's pointing there the temp is only 190 degrees.

 

Hmmm, not sure I've ever heard that phrase before...




You are certainly making progress, but I still think the indication is the majority of the issue. The new cooling fan clutch helped a little but only lowered the coolant temperature by 10 degrees. Even slightly warmer at 200F, the engine would not have been overheating. The needle should have never pegged high.

Was the gauge showing an overheat? Seems to be. 200F would normally be about right in the middle, with the needle pointing straight up. For 190F, expect to see the needle pointing a little to the left, usually around the O in NORMAL.

The gauge itself is generally quite robust. If the oil pressure and fuel level gauges seem accurate, most likely you're looking at a bad temperature sensor. Spring for a genuine Motorcraft brand sensor, part #SW-2328. It's a whopping $15 at RockAuto:

https://www.rockauto.com/en/moreinfo...t=4748&jsn=958

Or $17 at Amazon:



Is your engine fuel-injected? If so, I think there's a separate temp sensor for the computer. It will have two wires and a plastic connector. Make sure you get the sensor that drives the gauge. It has a single wire with a 90 degree rubber boot:




Also, you had previously mentioned coolant venting into the overflow tank. Did you ever pressure test the cap? Sure seems like it was venting early. If you don't want to test the cap, I'd at least spring for a quality replacement and see if that helps.