HELP New Temp sensor says I'm running a bit warm.........

[Anonymous]

I have a 67 Mustang 6 cyl auto Convert with no AC and I just did the following work:

New 3 core radiator (from a 2 core)
New 6 Blade fan (1" from radiator)
New T-Stat 180 deg.
New Temp sending unit ("high quality" from Must Unlimited)

It runs like a top now, but im concerned about the temp reading. My old sending unit had no reading because it was broken. This one quickly rises to 80% between C and H at idle in 85 degree weather and seems to stay there. Any thoughts????????

 

[250mav]

so the gauge just has a sweep, doesnt have actual numbers on it? either the gauge is not functioning right or your actually hot. look at the tstat for dirt or rust that may be blocking it, even though you rad is new you might still have "crap" in the block. it has been hot and your engine does get the hoter when your sitting with no airflow through the rad. whats your reading when your driving it? just thinking out loud here

 

[MustangSix]

That may be about right with a 180 thermostat. A 160 "usually" lands in the middle of the gauge. The stock gauge is not the most reliable measuring tool.

 

[Anonymous]

I flushed the engine twice before changing the thermostat, rad, hoses and fan. It is a sweeping gauge and it's 80% of the way to H at idle. I drove it for a short ride and it didnt seem to change the temp.

 

[cfmustang]

Just because the sender is new (and supposed to be the high quality model) does not necessarily make it accurate. Like someone previously said, the stock gauge is not the best measurement.

The only way to know for sure is a thermometer reading from the radiator.

 

[MercuryMarc]

If you mount a "temporary" aftermarket temp sensor instead of the stock one, you can get your colling issues addressed and then eventually go back to the stock gauge. It's been a few years and I am still using my "temporary" gauge- still woking out my issues, but I feel better knowing the actual temp.

Good Luck!

 

[MustangSix]

You can also try other senders to "calibrate" the gauge. Some read higher, some read lower. There is a small adjustment screw on the gauge itself, but I recommend you not mess with it.

 

[Anonymous]

Some folks on other cars place some resistors in-line to help "calibrate" the sending units. However sending units do not have a linear response and a resistor may make it read correct in one part of the scale but not the other. Besides, "C" & "H" are not very quantitative to calibrate too.
You might try a sending unit off of an old junk engine. My Mustang did not read within range with the new sending unit. I pulled one off of an old '73 Comet engine and it reads mid scale now. In the 100 degree heat with the AC on, the temp will creep up into the 80% range on the scale, but I do not boil over.
Doug

 

[JackFish]

My aftermarket (Hastings) guage sits around 240 in the city, and creeps up to 260 :!: on the highway. I'm running a 195* thermostat, 16lb cap, and it has never boiled over. The overflow tank is completely dry. The unit seems to be quite sensitive and regularly moves up and down a little.
I think this is partly due to the sender not reaching far enough into the head, and the reading I get is really a cylinder head temp, rather than a coolant temp. I have another guage to try, but so far no problems. Pretty tough little motor.

 

[Anonymous]

Even with the "80%" reading, it seems to be running very strong. This car had a serious cowl leak and lived outside thru New England Winters. I'm wondering if there's corrosion on the gauge........ but even with corrosion, it would give a lower reading right?



My 04 f150 was giving me a 50% reading in the same weather so maybe it's just the way it is.........

 

[Does10s]

Get one of those laser gun temp sensors and point it at the thermostat housing. It'll give you a very close temputure to the actual water temp.
Then put a little mark on your gauge at that location.
Will

 

[Anonymous]

............. is at the rear of the head. Will that give a false read?

 

[Anonymous]

good old meat thermometer

oil dipstick tube 183 deg
cyl head on lh side between 4 and 5 143 deg
Radiator top tank 165 deg
tstat housing 143 deg

all external measurments except oil dipstick tube

fyi 180 deg t stat

 

[CobraSix]

I should start cutting and pasting my blurbs about TSU's.

First, don't rely on them for an exact measurement. Unless the scale is graduated on the gauge they don't really mean much. Most TSU's only have a very small range of accuracy, and usually only in the desired operating temp range of the engine (say 140-210* for these engines). The voltages in that range can vary greatly and since each dash gauge is slightly different they will read differently. Take for instance a test I ran a few years back when I was troubling shooting a cooling problem. I had my old TSU that would read 3/4 to Hot while my mechanical gauge that I temporarily installed was realy 180*. I installed a new one and it woudl read 1/3 of the way from C at the same operating temp. This was after my complete overhaul of my cooling system.

If you think you may be overheating, get a cheap mechanical gauge from any discount auto parts store and install it, even temporarily, to check your running temperatures. If you do indeed have a cooling problem, my suggestion is to do a complete overhaul on the system unless you know for sure all of the components are less then 20 years old. These systems corrode. Replace radiator, water pump, hoses, T-Stat, and TSU. With all of those things in good workind order, you really have no need for fancy fan systems, shrouds, or water wetter type stuff. The only downside to having a good working cooling system is if you are like me, living in a cold winter area and drive your car in the winter, your heat sucks. My mustang doesn't heat up above 140* in the winter which makes for cold rides. I usually have to block part of the radiator off to get it running warm.

Slade