Sorry If this is a stupid question but I'm a noob with mechanic work. I am replacing the thermostat on my 98 Nissan 200SX. I bought both a gasket and blue rtv silicone made to make or seal your own gasket. Should I use both together or just one. My intuition tells me I can just use the gasket but I want to be sure

  • Welcome to Motor Vehicle Maintenance & Repair! Not a stupid question at all! Commented May 16, 2018 at 16:21

2 Answers 2


Since the thermostat in your car has a regular gasket, you can use RTV or not, at your pleasure. If you've had seepage issues in the past, it's almost a given you'd use it. Even if you haven't, it's not going to hurt anything to use it now. If you do use it, only put a thin coat on it, covering both sides evenly. If you put too much on it, you can cause yourself issues. When you tighten down the housing, don't over tighten it. If you start seeing sealant squishing out, you've gone too far. Just bring the bolts down snug and you should be in pretty good shape. While I don't have the spec, I doubt you'd need to torque them beyond 20 lb-ft. You really don't need a torque wrench to tighten these, just try to make them as even as your calibrated hands can and it should be fine. Once the engine has gone through a heating cycle, double check to ensure they are still snug and you should be golden.

  • Alright thanks I think that clears it up. I guess what I was asking though is I shouldn't use both together right? I should instead use either or. You don't typically put silicone on a gasket right?
    – Cam Jones
    Commented May 16, 2018 at 17:30
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    You absolutely can put sealant on the gasket if you want to. I will more often than not put a skim coat on a gasket so it will seal that much better. The only downside to using sealant is if/when you ever have to change it out again, you have to clean it all up before you can replace the gasket, or you'll most likely incur a leak. Also, you don't use sealant on rubber type gaskets unless specified (there are a few exceptions to this, but not really pertinent for this discussion). Commented May 16, 2018 at 18:10
  • Certainly okay, but I prefer a non-setting goop like Hylomar, or even easier - the spray on gasket sealer (usually red or blue) on both sides for that perfect THIN coat. Little known secret: spray "DIsk Brake Quiet" in blue or red can is exactly the same stuff, and usually costs less that the same can with "Gasket" in the label.
    – SteveRacer
    Commented Jun 8, 2018 at 3:32
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    @SteveRacer - I was talking mainly about fiber gaskets ... I usually don't use anything on rubber (or synthetic rubber) gaskets or anything metal (except for maybe copper spray on for MLS head gaskets depending on the application). Most anything like a head gasket requires it maintain a thickness or you risk warping a head ... not worth it. Spray on stuff stays fairly uniform, so it's not a bad thing. Commented Jun 8, 2018 at 19:03
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    @Pᴀᴜʟsᴛᴇʀ2 understood; agreed. The OP didn't make the distinction (but we both probably assumed correctly). Belt and suspenders (and lose some weight) is my common mantra. No problem on a flat gasket; no need if it's one of those slotted square-cut orings. (There's probably a proper name for those... I don't know it... I'm ashamed.)
    – SteveRacer
    Commented Jun 11, 2018 at 7:15

Cant do ye any harm to use a little on original gasket

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