Changing Thermostat and using Sealer? - Ford Mustang Forum
LinkBack Thread Tools
post #1 of 6 (permalink) Old 10-12-2012 Thread Starter
Classic Member
joshuastangs's Avatar
Joined: Feb 2010
Location: Los Angeles
Posts: 89
Changing Thermostat and using Sealer?

So im going to be changing my 1988 302 thermostat and i noticed in a few videos on youtube of people replacing it. They use some sort of sealer on the housing that they put the gasket over once they've replaced and are ready to put everything back together. They use some sort of silicone? or rtv sealer?

So before i replace my thermostat, can anyone recommend the proper sealer i should use to seal this thing right please.
joshuastangs is offline  
Sponsored Links
post #2 of 6 (permalink) Old 10-12-2012
SHELBY GT 350 Member
5.0L Member
need4spd90's Avatar
Joined: Apr 2009
Location: Mountain Top
Posts: 6,337
permatex ultrablack rtv or "the right stuff". you dont even need a gasket with either of the two

1987 Notchback - N/A stock 302, TFS heads, Holley Systemax, FTI cam, Astro A5
Best so far: 10.92 @ 123mph with a 1.49 60ft
need4spd90 is offline  
post #3 of 6 (permalink) Old 10-12-2012
5.0L Member
cmc87's Avatar
Joined: Jan 2010
Location: Montreal
Posts: 480
I didn't use any sealant, just the gasket. Made sure all surfaces were nice and clean first. Spray of gasket remover and a razor blade.
img 2
No leaks.

Anyways to actually answer your question, like need4spd said, Permatex ultra black RTV.
cmc87 is offline  
post #4 of 6 (permalink) Old 10-12-2012
PONY Member
5.0L Member
robs91fox's Avatar
Joined: Oct 2007
Location: Pomfret
Posts: 299
Personally, I like to use the Permatex high heat RTV (The red stuff) buts thats just personal preference.

Also, specifically on the thermostat housing make sure its SUPER clean. This is a spot that loves to leak if you don't clean it up perfect.

1991 GT: Trick Flow Track Heat Heads, Trick Flow Stage 1 cam, Ported GT40 Intake, 1.6 Rockers, 24 lb. injectors, 190 LPH Fuel Pump, BBK 70mm TB, BBK Headers, Off-road H, Flowmasters, 3.73's, Eibach Springs, Hotchkis Control Arms, FRPP Alumuinum D/S

2007 GT California Special: Steeda axle-back, K&N cold air
robs91fox is offline  
post #5 of 6 (permalink) Old 10-12-2012
SHELBY GT 500 Member
5.0L Member
Smurf stang's Avatar
Joined: Apr 2009
Location: Miami
Posts: 13,092
If you use one don't use the other. It always works best with either just the gasket or just the rtv.

Once you go ultra black you never go back.

2014 V6 Deep Impact Blue Mustang, Borla Type S, 2.73 (Uughh need 3.73)
1989 Sonic Blue Mustang LX Coupe, 349 ci,
392 rwhp 424 rwtq....Mustang Dyno
"There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves." -Will Rogers-
Smurf stang is offline  
post #6 of 6 (permalink) Old 10-12-2012
RotaryStang's Avatar
Joined: Jun 2010
Location: Wilmington
Posts: 191
Iv found what works the best is to yes clean the surface very well where the gasket lays. Be careful not to ruin the surface with sandpaper, razor blade, etc..very easy to make the surface uneven. If you look closly there are little levels where the thermo and gasket lay perfectly. Next take the smalliest amout possible of the gasket maker and put it on the lower intake where the gasket would lay. You only want to use it for the gasket to stick in place. You just want it sticky not globbed on or even a layer. Just sticky enough for the gasket to stay. If anything put three pin size dots of the goo. thats all you need. Then continue the rest of the procedure like you would normally. If its going to be cold where you live i would suggest not putting a 180 thermo in for the winter. Your car will never get up to running temp and winter. not good!!!! A lot of people make that mistake. The thermostat is a very cheap part like spak plugs but is very important to your motor like plugs!!!

98 merc mountaineer short block, E7 heads, b cam, 19lb. EV6 injectors, 75mm tb, 75mm EGR delete spacer, stock maf, screamin demon coil, ford racing 8.8mm. plug wires, autolite #25's, 3.73 rear, refurbed t-5 trans, steeda tri-ax shifter, stage 2 clutch kit, lakewood drag suspension, sve upper and lower control arms, v6 contour fan, bbk shorty headers, bbk catless x-pipe, flowmaster 40s to dumps, 3G 130 alt, welded and bolted subframe connectors
RotaryStang is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Ford Mustang Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a VALID email address for yourself, otherwise you will not receive the necessary confirmation email needed to confirm, validate and activate your new AFM member account.

Failure to provide a VALID email address, will result in the cancellation of your new AFM member account registration.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

For the best viewing experience please update your browser to Google Chrome