What is this red sealant?


 
Evan Kornacki

Evan Kornacki

New member
Does anybody know what this red sealant is, and where I can buy more of it? It comes pre-applied from the factory on Weber gas control valves (at least on the Spirit front-control grills.) It almost looks like some kind of RTV silicone, but I'm not sure if RTV will resist propane (I know silicone won't resist gasoline ... so I'm suspicious. I want to know for sure before I replace it.)

DSC_3636.JPG
 
I don't think it is a "Sealant" such as Red Hi-Temp RTV. I beleive it is a rubber/silicone gasket. I am skeptical that you would find a source for them without sourcing a whole new valve.
 
Bruce said:
I don't think it is a "Sealant" such as Red Hi-Temp RTV. I beleive it is a rubber/silicone gasket. I am skeptical that you would find a source for them without sourcing a whole new valve.
Click to expand...

No, its definitely some kind of chemical that is hand-dispensed (like from a caulk gun) onto the valve. Its not a pre-made gasket. See the close-up below. Any ideas what they use?

DSC_3639.JPG
 
It's simple red RTV high temp. LP/NG are not gasoline or a liquid state so they have no solvent properties at all. Just go to any automotive supply place and get a tube of red RTV. Now whatever you do, if you decide to use any of it on your car.........................STOP! Beware red RTV is NOT sensor safe meaning if you use it anywhere the "off gasses" can make it into the intake stream it will foul your O2 sensors and likely the MAF sensor as well. But on a grill there are none of those things
 
LMichaels said:
It's simple red RTV high temp. LP/NG are not gasoline or a liquid state so they have no solvent properties at all. Just go to any automotive supply place and get a tube of red RTV. Now whatever you do, if you decide to use any of it on your car.........................STOP! Beware red RTV is NOT sensor safe meaning if you use it anywhere the "off gasses" can make it into the intake stream it will foul your O2 sensors and likely the MAF sensor as well. But on a grill there are none of those things
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Are you sure?

I've been doing some Google-ing and it appears that silicone—maybe including Room-Temperature-Vulcanizing (RTV) silicone—is not compatible with propane. I don't want to put the wrong thing on there.

O-Ring-Chemical-Compatibility-Guide-Marco-Rubber.png

If you look at the above chart from Marco Rubber, it looks like Teflon, Viton, Urethane, and even Buna are compatible (as well as something I've never heard of called "Aflas")
 
It's silicon
Evan Kornacki said:
Are you sure?

I've been doing some Google-ing and it appears that silicone—maybe including Room-Temperature-Vulcanizing (RTV) silicone—is not compatible with propane. I don't want to put the wrong thing on there.

View attachment 112215

If you look at the above chart from Marco Rubber, it looks like Teflon, Viton, Urethane, and even Buna are compatible (as well as something I've never heard of called "Aflas")
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Believe me it'd red RTV like Bruce posted above. Sometimes Google is not your friend. It's misleading you. But hey, you do whatever you want or believe what you want.
 
LMichaels said:
It's simple red RTV high temp. LP/NG are not gasoline or a liquid state so they have no solvent properties at all. Just go to any automotive supply place and get a tube of red RTV. Now whatever you do, if you decide to use any of it on your car.........................STOP! Beware red RTV is NOT sensor safe meaning if you use it anywhere the "off gasses" can make it into the intake stream it will foul your O2 sensors and likely the MAF sensor as well. But on a grill there are none of those things
Click to expand...
Need to disagree with you here Larry. Correct me if I'm wrong but unless MAF technology has changed dramatically since I've been out of the repair business, I see no way it could damage or cause any adverse effects to A MAF sensor unless it actually came into contact with the functional elements of it. which would be highly unlikely.

Isn't Permatex Ultra-Red sensor safe. Or am I confusing it with Ultra-Copper?
 
Bob Bailey said:
Need to disagree with you here Larry. Correct me if I'm wrong but unless MAF technology has changed dramatically since I've been out of the repair business, I see no way it could damage or cause any adverse effects to A MAF sensor unless it actually came into contact with the functional elements of it. which would be highly unlikely.

Isn't Permatex Ultra-Red sensor safe. Or am I confusing it with Ultra-Copper?
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I'm going back to my wrenching days. Red sensor safe did not exist. I honestly (until Bruce posted that link) did not even know red sensor safe existed. I stopped wrenching like over 20 years ago. So that is the reference point I was coming from
 
After more thinking, I'm pretty sure GM used it as valve cover gaskets for their Target Master crate engines at least into the early 80s. What a disaster those were!
I closed the shop and quit wrenching in early 2002.
 
Cody Bratton said:
If a company like permatex says it’s sensor safe, I’d trust it. They make some damn fine products.
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I would as well. I've always trusted their stuff. But, like I noted back when I was still doing it, none of the red was safe. So, I simply threw it out there from memory. I haven't bought the stuff in more years than i care to count :D
 
Cody Bratton said:
If a company like permatex says it’s sensor safe, I’d trust it. They make some damn fine products.
Click to expand...

I have no doubt that Permatex Ultra Red is sensor-safe; but it doesn't appear to be propane-safe.

In fact, I don't think any RTV is propane-safe, because they're all based on Silicone Rubber, and every chemical compatibility chart that I can find says that Silicone Rubber is incompatible with Propane ... along with Methane (Natural Gas), Hexane (Gasoline), and Butane.

Its not Google or A.I. saying this, its o-ring manufacturers.

I found these pre-made on GrillP@rtsSearch and they're only $3 each so I'm going to buy some of them. Hopefully they're made of the right kind of rubber.

Screen Shot 2025-05-06 at 6.25.14 PM.png
 
I use RTV Ultra Copper on just about anything high temp.

1746840229437.png


PRODUCT DESCRIPTION
Permatex Ultra Copper is a single component, room
temperature vulcanizing gasketing compound designed to
provide reliable “formed-in-place” gaskets for mechanical
assemblies. This material cures on exposure to moisture in the
air to form a tough, flexible, silicone rubber gasket. The
product resists aging, weathering and thermal cycling without
hardening, shrinking or cracking. Permatex Ultra Copper is
the most advanced high performance, high temperature (up to
700F intermittent) RTV gasket available.

PRODUCT BENEFITS
• High temperature resistance
• Sensor safe, non-corrosive
• Superior adhesion and flexibility
• Replaces most cut gaskets
• Improved oil resistance
• Can be used as a gasket maker or dressing
• Non-flammable, Non-toxic
• Low odor
TYPICAL APPLICATIONS
• Pumps
• Compressors
• Exhaust manifolds/headers
• Valve covers
• Oil pans
• Thermostat housings
• Gearboxes

 
DanHoo said:
I use RTV Ultra Copper on just about anything high temp.

View attachment 112311


PRODUCT DESCRIPTION
Permatex Ultra Copper is a single component, room
temperature vulcanizing gasketing compound designed to
provide reliable “formed-in-place” gaskets for mechanical
assemblies. This material cures on exposure to moisture in the
air to form a tough, flexible, silicone rubber gasket. The
product resists aging, weathering and thermal cycling without
hardening, shrinking or cracking. Permatex Ultra Copper is
the most advanced high performance, high temperature (up to
700F intermittent) RTV gasket available.

PRODUCT BENEFITS
• High temperature resistance
• Sensor safe, non-corrosive
• Superior adhesion and flexibility
• Replaces most cut gaskets
• Improved oil resistance
• Can be used as a gasket maker or dressing
• Non-flammable, Non-toxic
• Low odor
TYPICAL APPLICATIONS
• Pumps
• Compressors
• Exhaust manifolds/headers
• Valve covers
• Oil pans
• Thermostat housings
• Gearboxes

Click to expand...
That would work as well. People confusing what LP safe is referring to. No, RTV silicone is NOT LIQUID LP safe it's safe against the gaseous form. But, no worries
 
Evan Kornacki said:
I have no doubt that Permatex Ultra Red is sensor-safe; but it doesn't appear to be propane-safe.

In fact, I don't think any RTV is propane-safe, because they're all based on Silicone Rubber, and every chemical compatibility chart that I can find says that Silicone Rubber is incompatible with Propane ... along with Methane (Natural Gas), Hexane (Gasoline), and Butane.

Its not Google or A.I. saying this, its o-ring manufacturers.

I found these pre-made on GrillP@rtsSearch and they're only $3 each so I'm going to buy some of them. Hopefully they're made of the right kind of rubber.

View attachment 112303
Click to expand...
That is good research. To be clear, I was only referring to it being sensor safe.
 
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