• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Is it running hot or not?

  • Thread starter Thread starter Stever89
  • Start date Start date Oct 26, 2010

Stever89

5 Year Member
Dec 14, 2009
536
9
39
Biloxi, MS
Oct 26, 2010
#1
  • Oct 26, 2010
  • #1
Let me try to sum this up with the least amount of cunfusion:

I got my coupe last December. At that time it used the factory coolant temp gauge (seemed to work fine). Later, I installed an aftermarket mechanical temp gauge, seemed to work fine too, reading 190.

I installed a fan controller two weeks ago, all's good.

This past week, I took the water temp gauge out and replaced it with another mechanical Jegs gauge to go in my gauge cage in the AC vent. It went to 240! Freaked me out. It didn't seem to be that hot, when a motor gets to 240+, things start smelling and smoking, none of that. I took the tstat housing off to check the tstat, there wasn't one! So I put in a good (checked it in a pot of water) 180 stat. Still went to 240 with the jegs gauge.

So I reinstall the first gauge, just mounted it temporarily under the hood and ran it up to the cowl, it reads 190 like it always did.

So I get a pot of water, put it on the stove and heat it to boiling, and with a known calibrated thermometer, I (carefully) take it outside and put both mechanical temp gauge probe ends in. They both read ~200F, which is good

So both gauges seem to be working accurately when submerged in a pot of hot water, but the jegs gauge goes nuts when it's installed in the manifold.

I know this is confusing, but is there some trick or something I'm missing in the installation of the Jegs probe? I see it has a rubber o ring, the first one did not.

Any suggestions advice is welcome.
 

2000xp8

SN Certified Technician
Aug 8, 2003
8,019
1,615
194
NJ
Oct 26, 2010
#2
  • Oct 26, 2010
  • #2
Where do you have the thermometer end screwed into?
 

Stever89

5 Year Member
Dec 14, 2009
536
9
39
Biloxi, MS
Oct 26, 2010
#3
  • Oct 26, 2010
  • #3
Into the top of what most of you call the lower intake (this is a carbed 302), driver's side front.
 

Stever89

5 Year Member
Dec 14, 2009
536
9
39
Biloxi, MS
Oct 26, 2010
#4
  • Oct 26, 2010
  • #4
Here's one thing I'm gonna do:

I'll run the factory sending unit into the fitting on the tstat neck. At least I'll have 2 sources of data now.
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
Oct 26, 2010
#5
  • Oct 26, 2010
  • #5
Just remember that the sender in the water neck will function contingent upon the t-stat opening.

What's different in the scenarios when you're running the guage in the cowl vs on the interior?
 

clement

Founding Member
Feb 27, 2001
1,106
52
59
Oak Cliff
Oct 27, 2010
#6
  • Oct 27, 2010
  • #6
is the sending unit correct?
 

Stever89

5 Year Member
Dec 14, 2009
536
9
39
Biloxi, MS
Oct 27, 2010
#7
  • Oct 27, 2010
  • #7
HISSIN50 said:
Just remember that the sender in the water neck will function contingent upon the t-stat opening.

What's different in the scenarios when you're running the guage in the cowl vs on the interior?
Click to expand...

No difference, I'm unscrewing one probe from one mechanical gauge and screwing the other one in it's place.
 

Stever89

5 Year Member
Dec 14, 2009
536
9
39
Biloxi, MS
Oct 27, 2010
#8
  • Oct 27, 2010
  • #8
clement said:
is the sending unit correct?
Click to expand...

Good question. There are different sending units? You mean different temp ranges? Sorry for ignorance, I'm learning as I go.
 
You must log in or register to reply here.

Similar threads

Engine Themostat
  • Mindseye007
  • Jan 30, 2026
  • Fox 5.0 Mustang Tech
  • 2
Replies
21
Views
697
Fox 5.0 Mustang Tech Feb 1, 2026
86HO5.0
8
Progress Thread Sask84gt's 84 GT - Questions and Progress Thread
  • Sask84gt
  • Oct 13, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
22
Views
546
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 6, 2026
Sask84gt
M
Engine 1988 Foxbody - Overheating Summer
  • MDrisc
  • Oct 26, 2025
  • Fox 5.0 Mustang Tech
Replies
10
Views
527
Fox 5.0 Mustang Tech Nov 28, 2025
Mustang5L5
T
Progress Thread 2002 Mustang 3.8L CV
  • TheIncompetentMechanic
  • May 26, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
1
Views
62
1996 - 2004 SN95 Mustang -General/Talk- Jun 1, 2026
TheIncompetentMechanic
T
Fox Help
  • 93fox85
  • Mar 22, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
5
Views
193
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Mar 23, 2026
Noobz347
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?