Got Real Hot But Luckily 302 Didn't Overheat - Vintage Mustang Forums
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post #1 of 26 (permalink) Old 07-01-2019, 10:00 PM Thread Starter
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Unhappy Got Real Hot But Luckily 302 Didn't Overheat

So today my months of work really got put to the test. Was in a nightmare scenario of grinding stop and go traffic for a very long time due construction on the way to the body shop some 50 miles away. Temperature 90F which is usually hotter out on the pavement, baking sun. No A/C either!

Temp guage ran up as far at it can go without actually touching the "H". Car didn't feel like it ran worse and there was no vapor lock. Just out of an abundance of caution I pulled over on grass, hood up and let her cool for 20 minutes or so. Did not make much difference but on I went. Once I got to normal moving traffic temps dropped to mid guage.

Any chance the guage or sending unit is off? It did not feel especially hot under the hood when I opened it up. I realize this has nothing to do with internal coolant temps. I run clean new 50/50 Prestone mix. I've got an new Aluminum 20" 2 Core 1.25" diameter core tubing radiator, full size fan shroud, 6 blade fan and a thermostatic fan clutch plus an overage coolant tank. Thought that this new setup would be the end of the high guage readings. So am I doing something wrong?

Most of the time while moving it's in the middle. Idling in driveway a long time it's 3/4 or a bit more. This was it's first real grit' n grind traffic during a nasty scorching rush hour.
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Last edited by jsbenami; 07-01-2019 at 10:10 PM.
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post #2 of 26 (permalink) Old 07-01-2019, 11:41 PM
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I would buy a $40-ish mechanical temperature gauge and temporary install it under the dash to find out what's going on. Since you seem to have covered all the other bases, what is the condition and stated temperature of the thermostat? Whenever I have something weird going on that is the first thing I change. The fact that it didn't puke is a good sign.
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post #3 of 26 (permalink) Old 07-01-2019, 11:57 PM
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If you didn't blow steam you did not overheat. You're good.
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post #4 of 26 (permalink) Old 07-02-2019, 12:48 AM
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Like mentioned above, put a mechanical gauge with actual temperature numbers on it, and you can also get a laser thermostat and check various areas around your engine for temp readings.



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post #5 of 26 (permalink) Old 07-02-2019, 12:49 PM
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Quote:
Originally Posted by jsbenami View Post
So today my months of work really got put to the test. Was in a nightmare scenario of grinding stop and go traffic for a very long time due construction on the way to the body shop some 50 miles away. Temperature 90F which is usually hotter out on the pavement, baking sun. No A/C either!

Temp guage ran up as far at it can go without actually touching the "H". Car didn't feel like it ran worse and there was no vapor lock. Just out of an abundance of caution I pulled over on grass, hood up and let her cool for 20 minutes or so. Did not make much difference but on I went. Once I got to normal moving traffic temps dropped to mid guage.

Any chance the guage or sending unit is off? It did not feel especially hot under the hood when I opened it up. I realize this has nothing to do with internal coolant temps. I run clean new 50/50 Prestone mix. I've got an new Aluminum 20" 2 Core 1.25" diameter core tubing radiator, full size fan shroud, 6 blade fan and a thermostatic fan clutch plus an overage coolant tank. Thought that this new setup would be the end of the high guage readings. So am I doing something wrong?

Most of the time while moving it's in the middle. Idling in driveway a long time it's 3/4 or a bit more. This was it's first real grit' n grind traffic during a nasty scorching rush hour.

Who knows how hot that is. That temp gauge just gives you a notion of what's going on.
I've had our '68 since my folks bought it new. It's always run a bit warm. (maybe 1/4"
to the left of center on the factory gauge normally, any bit to the right I considered hot)

I'm surprised you didn't take the two side panels out and go for the 24" wide "big block"
radiator. That would have gained you some additional capacity.

I've got a 20" in mine but it's a copper brass truck core and weighs something like 40#.
It does cool spectacularly though. I've never seen above halfway even when it's 110 outside.
(factory shroud, mechanical fan clutch and 6 blade fan)

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post #6 of 26 (permalink) Old 07-02-2019, 02:34 PM
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They are referred to as idiot lights for a reason...useless without numbers...not to mention, the factory gauges are not known for being accurate at all. I myself would NOT put a mechanical temp gauge(or ANY mechanical gauge aside from vacuum/boost) inside my vehicle(you are asking for burns in the case of a leak) but any good electrical aftermarket gauge will do the trick...or, if avoiding aftermarket gauges, as mentioned above, a laser thermometer will tell the real story...or closer than the factory idiot light.
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post #7 of 26 (permalink) Old 07-02-2019, 02:44 PM
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A mechanical temp gauge does NOT bring hot coolant into the interior of the car.

Sent from my LG-D631 using Tapatalk
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post #8 of 26 (permalink) Old 07-02-2019, 03:17 PM
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Quote:
Originally Posted by Jeff351w View Post
A mechanical temp gauge does NOT bring hot coolant into the interior of the car.

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I have never used one...I know that mechanical oil pressure gauges DO bring hot oil into the car, so I assumed the mechanical water temp gauge did as well.

Last edited by wicked93gs; 07-02-2019 at 03:23 PM.
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post #9 of 26 (permalink) Old 07-02-2019, 03:28 PM
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You can also adjust the gauge to correspond to the ohm values shown in the attached chart. You'll need an inexpensive variable resistor along with your digital multimeter. Here's a link to a decent, but inexpensive one: https://www.amazon.com/JANSANE-Poten...1-2-spons&th=1

I would grab a scrap piece of speaker wire or lamp cord and connect the wires to the #1 and #2 terminal on the Potentiometer. Leave the #3 terminal disconnected. On the other end of the speaker wire or lamp cord I'd attach alligator clips.

Now, the two calibration "wheels" are behind the holes shown at the 2 and 8 o'clock positions in the photo. The hole at 8 o'clock is used to adjust to the LOW limit. The hole at 2 o'clock is used to adjust to the HIGH limit.

You want to use your DMM to adjust your potentiometer first to 78 ohms. Next, you want to disconnect the sending unit wire at the gauge. Turn the key switch to the "ON" position then connect one of your alligator clips to the empty terminal on the gauge and the other to ground. Now, adjust the needle on your gauge to just a hair below the line at "C". Disconnect your "Pot" and reset it using your DMM to 10 ohms. Once done, reconnect it to your gauge and adjust the needle to just above the line at "H". Disconnect your "Pot" and reconnect the gauge. You're done.

Yes, you can also use the same procedure to adjust your FUEL and OIL PRESSURE gauges.
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File Type: jpg Untitled.jpg (57.0 KB, 7 views)
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post #10 of 26 (permalink) Old 07-02-2019, 04:23 PM
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Quote:
Originally Posted by Woodchuck View Post
You can also adjust the gauge to correspond to the ohm values shown in the attached chart. You'll need an inexpensive variable resistor along with your digital multimeter. Here's a link to a decent, but inexpensive one: https://www.amazon.com/JANSANE-Poten...1-2-spons&th=1

I would grab a scrap piece of speaker wire or lamp cord and connect the wires to the #1 and #2 terminal on the Potentiometer. Leave the #3 terminal disconnected. On the other end of the speaker wire or lamp cord I'd attach alligator clips.

Now, the two calibration "wheels" are behind the holes shown at the 2 and 8 o'clock positions in the photo. The hole at 8 o'clock is used to adjust to the LOW limit. The hole at 2 o'clock is used to adjust to the HIGH limit.

You want to use your DMM to adjust your potentiometer first to 78 ohms. Next, you want to disconnect the sending unit wire at the gauge. Turn the key switch to the "ON" position then connect one of your alligator clips to the empty terminal on the gauge and the other to ground. Now, adjust the needle on your gauge to just a hair below the line at "C". Disconnect your "Pot" and reset it using your DMM to 10 ohms. Once done, reconnect it to your gauge and adjust the needle to just above the line at "H". Disconnect your "Pot" and reconnect the gauge. You're done.

Yes, you can also use the same procedure to adjust your FUEL and OIL PRESSURE gauges.
This is cool, thanks @Woodchuck!!

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Engine: 1980 302 bored 0.060, so 311 ci. 351 heads, Holley 670 cfm 4 barrel, Eldebrock Torker II 289 intake, Competition Cam 276 duration 490 lift.
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post #11 of 26 (permalink) Old 07-03-2019, 08:33 PM Thread Starter
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@GT289....did not go with the 24" because I was told by numerous folks including the NPD guys at Michigan (best of their stores for knowledge) and Rick here on the Forum that buying a 24" was an overkill for my stock-ish rebuilt 302 even with an aftermarket A/C (which has not yet been reinstalled). If the guys who sell you a rad aren't saying you need the pricer one then it's probably not necessary. The 20" with the thick core 1.25" 2 row aluminum tubing vs old Copper Brass w/3 row .25" core is supposedly vastly better at cooling. With my 3-core copper/brass it would not overheat but was running hotter in cool weather so I decided to chuck it. When it was in use it had the non-clutched fan and I still wonder how much better of a job at idle the non-clutch fan would do.


@Nailbender Thermostat on this Pony is 180F and it's a quality brand new one installed with when I put the trappings onto the rebuilt 302. Unfortunately I don't know if this thing is bored .30 or .60 over. I just know it had run once on a bench test.

Yeah wow, seems like the consenus it to get a AM type guage put in somewhere. I was thinking of looking for one that that mounts into one of my 3/8" NPT intake fittings and having a temporary wire going into the car or just looking at it through the windshield next time I'm in traffic. Fortunately I mostly avoid this type of 'FML' traffic that I was stuck in for well over 1 hour. If she didn't overheat I think that's a great sign.

Last edited by jsbenami; 07-03-2019 at 08:52 PM.
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post #12 of 26 (permalink) Old 07-03-2019, 08:35 PM Thread Starter
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@Woodchuck, I'm definitely copying and pasting your post and I WILL adjust that thing when I have the dash out to fix the wildly innacurate stuck odometer. That will be a great time to knock that out and refresh the framing, glass, trim and anything else in there that looks like it needs restoration. I had no idea at all that these are adjustable.
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post #13 of 26 (permalink) Old 07-03-2019, 08:40 PM
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I know your pain, as I live in DC and drive to Tyson’s every day. I dont drive the Mustang to the office all that often, but did take it last Friday and hit more traffic than expected while the outside temps hit 100. I do have an electric fan which seems to help a lot. Sadly, the DC area isn’t meant for cars like this...... Good luck!

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post #14 of 26 (permalink) Old 07-03-2019, 09:16 PM
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Quote:
Originally Posted by Quicksilver66 View Post
Sadly, the DC area isnt meant for cars like this...... Good luck!
Strange.... Ford sold a TON of 'em....

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post #15 of 26 (permalink) Old 07-03-2019, 09:23 PM Thread Starter
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@Quicksilver66.....Mine is probably as bad or worse. I live in Alexandria and drive up to Ft. Meade 3 days a week. But never use the Mustang to commute, just on account of the (not converted yet) drum brakes and other obvious things. I take it up there to the base auto shop on weekends to do major work on it.

But this particular trip was from my father's garage in Silver Spring to a body shop in Pasadena, MD. Thought I left early enough to avoid the insaneballs traffic of the Baltimore and Montgomery County a construction mess plus holiday traffic caused a nasty jam on RT 100 near Glen Burnie. Hell traffic even by our standards. It was about 95F out. I'm impressed it ran smoothly through the grind....but that guage gave me some unwelcome stress and it was toasty without any A/C in that black interior.
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