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

just changed thermostat...now leaking

  • Thread starter Thread starter robertdeuce
  • Start date Start date Jul 17, 2011

robertdeuce

Member
Jul 10, 2011
147
2
19
Jul 17, 2011
#1
  • Jul 17, 2011
  • #1
so i spent a few hours changing the thermostat and flushing the rad.
did everything right. i put on a new gasket and some black rtv.
tightened the nuts and re-connected the hose but now its leaking.
was i suppose to let the rtv cure?
thanks
 

vristang

15 Year Member
Mar 31, 2005
4,933
101
124
Seattle
Jul 18, 2011
#2
  • Jul 18, 2011
  • #2
robertdeuce said:
did everything right. i put on a new gasket and some black rtv.
Click to expand...
well, if you had done everything right... it probably wouldn't leak...
couldn't resist...



Make sure that the stat didn't slip out of place. If it moves out of its groove in the housing, then the entire housing won't seat/seal properly...
 

FoMoCo17

Member
Apr 1, 2011
188
3
18
Jul 18, 2011
#3
  • Jul 18, 2011
  • #3
The factory thermostats actually could be installed and twisted to lock them into the housing. If you installed an aftermarket thermostat, it may have slipped out and is between the housing and block causing the leak. Or, hopefully you didn't tighten it too much if this occured because then you could have cracked the fragile housing. And, a new one is not too cheap ... around $90 at the dealer.

Normally, I will put some kind of sealer on the thermostat the night before and seal it in place and put it on the following day ... two drops of super-glue works great the night before. It holds it in place for installation and is easy to remove when replacing the thermostat. I'd take it aprt and inspect the housing and sealing ... should be easy to spot the problem. But, check the housing carefully to make sure you did not crack it tightening it with the thermostat not seated properly.
 

wythors

Get off my lawn!!!
Founding Member
May 17, 2000
2,277
35
69
C Addle
Jul 18, 2011
#4
  • Jul 18, 2011
  • #4
Since you didn't specify where the leak is coming from, we can't know for sure. But if the leak is coming from the t-stat housing area, then both guys above nailed it.
 

robertdeuce

Member
Jul 10, 2011
147
2
19
Jul 18, 2011
#5
  • Jul 18, 2011
  • #5
its from the housing yes... do i need the gasket and the rtv or can i use just the rtv? do i let it harden before driving it?
 

4rdnut

Member
Dec 14, 2010
188
1
16
Jul 18, 2011
#6
  • Jul 18, 2011
  • #6
Take the t-stat housing off again, remove t-stat and clean the groove in the housing. I use a sharp nail and run it around the corner of the groove to get out all corrosion and calcium deposits. Then clean both the intake and t-stat housing flat surface of any sealer. take the t-stat and lay it flat in the housing groove with copper pellet and spring up, then take high tack sealer and smear it on the flat surface of the t-stat housing, avoid getting any on t-stat, lay the new gasket on the t-stat housing and align the holes of gasket and housing with the bolts and let the sealer tack up real good. you now have the t-stat in the groove of housing with the gasket over t-stat setting up, so you can easily place the housing with t-stat and gasket up to the intakes flat surface aligning bolt holes and putting bolts back in.
 
You must log in or register to reply here.

Similar threads

B
2001 v6 New compressor issue
  • badmech
  • Apr 30, 2026
  • SN95 V6 Mustang Tech
Replies
0
Views
83
SN95 V6 Mustang Tech Apr 30, 2026
badmech
B
Resolved Got Too Hot!!!
  • PonyGTrider
  • Apr 27, 2025
  • Fox 5.0 Mustang Tech
Replies
7
Views
580
Fox 5.0 Mustang Tech May 6, 2025
PonyGTrider
M
Engine 1988 Foxbody - Overheating Summer
  • MDrisc
  • Oct 26, 2025
  • Fox 5.0 Mustang Tech
Replies
10
Views
519
Fox 5.0 Mustang Tech Nov 28, 2025
Mustang5L5
B
Engine Strange Noise
  • burntokita
  • May 8, 2026
  • Fox 5.0 Mustang Tech
Replies
8
Views
355
Fox 5.0 Mustang Tech May 11, 2026
keel
S
Drivetrain 8.8 Pinion and 302 rear main seal leaks after replacing. 93 5.0 with t-5
  • Steigy4827
  • Jun 23, 2025
  • Fox 5.0 Mustang Tech
Replies
10
Views
637
Fox 5.0 Mustang Tech Apr 1, 2026
Steigy4827
S
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?