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

anyone have issues with mr. gasket thermostats

  • Thread starter Thread starter 90mustangfan
  • Start date Start date Jan 3, 2008

90mustangfan

New Member
Oct 18, 2005
93
0
0
So cal
Jan 3, 2008
#1
  • Jan 3, 2008
  • #1
I had a bad hose and I figured while I was replacing my hose, I change the thermostat...I had a 195* stocker in there and It would run at the M. Now I put a 180 mr gasket thermostat and it runs at the first bar above 130..Is this normal?...I had the same therm in another car and it would run at the A...why is this one running so cold, Its a 180* for sure, shouldnt it run at the A mark....could this also be cause its winter and it will take a really long time to get to full temp? anyone have any issues with this therm?
 

bloopbloob

Member
Sep 27, 2006
578
4
16
Alberta
Jan 3, 2008
#2
  • Jan 3, 2008
  • #2
mines not a Mr. Gasket, but the old one ran fairly high on the gauge, my new 180* looks like the car never heats up, especially now that its winter, but it did it in the summer also. only time the needle would go over 1/2 was was after a good 30-45 min of HARD running (many 750-5000+ rpm pulls). The stock gauges are notorious for being WAAAAY off.
 

5spd GT

"the 5.0 owns all"
Founding Member
Aug 7, 2002
9,516
6
99
Arkansas
Jan 3, 2008
#3
  • Jan 3, 2008
  • #3
I never had an issue, but I used the factory guage.
 

Fast63

New Member
Sep 20, 2007
717
0
0
Jan 3, 2008
#4
  • Jan 3, 2008
  • #4
does your heater blow hot air? If it really is running that cold, the thermostat is probably stuck open. Will it get to that point within 5 minutes or does it take 20? How long have you driven it at one time and it has not been past that point?
 

cevtv

Founding Member
Sep 15, 2002
1,113
0
37
Massachusetts
Jan 3, 2008
#5
  • Jan 3, 2008
  • #5
90mustangfan said:
I had a 195* stocker in there and It would run at the M. Now I put a 180 mr gasket thermostat and it runs at the first bar above 130..Is this normal?...I had the same therm in another car and it would run at the A...why is this one running so cold, Its a 180* for sure, shouldnt it run at the A mark....
Click to expand...


First of all, get a real gauge and see where it really is - then worry about it if it's low.
 

5spd GT

"the 5.0 owns all"
Founding Member
Aug 7, 2002
9,516
6
99
Arkansas
Jan 3, 2008
#6
  • Jan 3, 2008
  • #6
Likely, if it is running different right after the thermostat install, the guage is reading what it would.

The chance of the guage going bad in that short of a time is unlikely.
 

90mustangfan

New Member
Oct 18, 2005
93
0
0
So cal
Jan 3, 2008
#7
  • Jan 3, 2008
  • #7
Well i have my heater core bypassed at the firewall, So no heat anyway...As for running I drove it a good 1 hr and take about 20min to get to temp. the the thermostat opens when the gauges is at the L, then it goes down alittle, then the thermostat closes, then it will climb back to the L...So the thermostat is opening and closing, It just seems the gauge is reading low....as my other stang with that same thermostat would read at the A...but then again this car has white faced gauges, so possible when I put the needle back I didnt put it exactly right...so
 

RYC CUKR

Founding Member
May 19, 2002
1,437
1
38
Orlando
Jan 3, 2008
#8
  • Jan 3, 2008
  • #8
I would get a mechanical gauge and check it with that. The stockers are notoriously inaccurate. Or it could be a sending unit that is on its way out

The Tstat is 15* cooler than the stocker so it should read a little lower but without a real gauge I wouldn't make any definitive decisions.

My 88 with a Mr Gasket 180* and an autometer mechanical gauge runs just a touch below 180*.
 

LiquidGT

Member
Oct 8, 2007
368
0
16
Near STL hell
Jan 4, 2008
#9
  • Jan 4, 2008
  • #9
I put a mr gasket 195* in my newly built motor, it was cold outsde and the temp was at the "L", I had no heat and I was concerned with ring wear. My mechanical gauge read 140* with the mr gasket. I put a stock style in and it warms up fine, I put the mr. gasket in a pot of water and it cracked opened at 180* and fully opened at 195*. I read somewhere else that the mr g. cracks open earlier and other people have the same problem.
 
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
751
Fox 5.0 Mustang Tech Feb 1, 2026
86HO5.0
8
M
Resolved 1988 Foxbody - Overheating Summer
  • MDrisc
  • Oct 26, 2025
  • Fox 5.0 Mustang Tech
Replies
16
Views
685
Fox 5.0 Mustang Tech Jul 17, 2026
fasterthangas
F
Resolved Got Too Hot!!!
  • PonyGTrider
  • Apr 27, 2025
  • Fox 5.0 Mustang Tech
Replies
7
Views
596
Fox 5.0 Mustang Tech May 6, 2025
PonyGTrider
S
Fuel ‘88 GT Runs Rich Cold — Fixes Itself When I Unplug Sensors (ECT, MAF, O2, etc.)
  • Sufarry
  • Nov 6, 2025
  • Fox 5.0 Mustang Tech
Replies
12
Views
856
Fox 5.0 Mustang Tech Nov 9, 2025
Mustang5L5
D
Resolved Upper radiator hose cold??
  • dqureshi06
  • Oct 31, 2024
  • Fox 5.0 Mustang Tech
Replies
14
Views
2K
Fox 5.0 Mustang Tech Nov 11, 2024
limp
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?