Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part MAY's Ride of the Month Challenge!

1 - 9 of 9 Posts

·
Registered
Joined
·
606 Posts
Discussion Starter · #1 ·
First of all, this is not a thread about solving a cooling problem and is just a question about the stock temperature gauge.

My 69 302 is very well behaved and the temperature gauge stays in the middle nearly all the time. But when I get stuck in some traffic for a fairly long time, it can creep above the middle.

So my question is what is regarded as being too hot on the gauge? Is it only when it hits the end of the scale, or is it before then? I know these gauges are probably not exactly accurate, but when should you start to worry things are getting too hot?

Jeremy.
 

·
Registered
Joined
·
606 Posts
Discussion Starter · #3 ·
When it goes past the end of the scale to the "H".
Well, that is reassuring. A few times now I have had it to about 3/4 of the way across the scale and I was starting to worry it was getting too hot. But it never went above this and I was stuck in traffic for quite some time.

Thanks.
 

·
Registered
Joined
·
183 Posts
Chances are the factory gauge isnt that accurate anyway. So, if you want to monitor actual temperature, which is probably a good idea, you may want to add a better quality numbered gauge.

With that being said, I had the gauges in my 71 ( with 351c ) calibrated by Rocketman and normal driving is usually towards the bottom of the middle range ( gauges in the 71 have a low, bigger mid range, then high).

This corresponds to about 190 on an Autometer gauge that is also installed. In traffic driving, the factory indicator usually stays below mid range.

If the gauge calibration is off, the above middle range may be accurate or way off.
 

·
Registered
Joined
·
532 Posts
There's a joke here somewhere about calibrating your gauge to Celsius, but damn if I can find it.

Side question (at the risk of highjacking the thread): If you don't have a numbered gauge and you were to measure temp with a laser, what is the best location? Thermostat body? Radiator? Inside the radiator?
 

·
Registered
Joined
·
606 Posts
Discussion Starter · #7 ·
There's a joke here somewhere about calibrating your gauge to Celsius, but damn if I can find it.

Side question (at the risk of highjacking the thread): If you don't have a numbered gauge and you were to measure temp with a laser, what is the best location? Thermostat body? Radiator? Inside the radiator?
I have one of those digital temperature devices, so I am also interested where you would point it. I am guessing where the temperature sender is in the inlet manifold, the thermostat housing or at the inlet area of the radiator.
 

·
Registered
Joined
·
2,468 Posts
Using an IR thermometer point it at the hose. When you use one it’s taking the temp from the surface of what you are measuring. When I measure the Mustang if I use metal fittings it’s 10* or so hotter than what the VDO water temp gauge says. If I use the hose the gauge and reading are within a degree or so. That technique is also speced in manufacturer service manuals.
 

·
Registered
Joined
·
507 Posts
Use your IR Temp Gun to measure the engine temperature at the location of the temperature sender, which I believe is on the intake manifold on your 69 302. A 70 Mach 1 (351C) should have it in the front of the block, just above the water pump - Not sure if this is the 'factory' location, but it's the best location for the most accurate engine temp reading.


Anyway, several readings will tell you what the temps are for various positions on the gauge.

Also, be sure you have the correct temperature sender. I replaced the temp sender once on my 66 289 with one from the local auto parts store, and all of a sudden the gauge readings were 1/4 to 1/2 the gauge higher than with the old sender. Even though I knew my actual temps were fine, it was unnerving to see the gauge reading so hot. I even installed a small secondary graduated temperature gauge just to confirm all was good. I now have a proper sender from one of the vendors that reads correctly.
 
1 - 9 of 9 Posts
Top