what is the half circle sensor with my thermostat?


Asked by Dec 26, 2013 at 09:44 PM about the 1995 GMC Vandura G25 Extended

Question type: Maintenance & Repair

i replaceed my thermostat & theres this flat peice of metal that looks like a sensor is
connected to it. It goes around half of the thermostat opening & the bolts go through it.
What is it & does it go between the housing & the manifold or does it go on the outside? I
was in a rush & cant remember.

10 Answers


I took photo, having difficulty uploading.

2 of 2 people found this helpful.

I'll try this again. This is the photo I took. I did notice with the photo that I think I need a gasket that goes around the thermostat it's self so it would sit in the hole better. I couldn't see that before. But even with that kind of gasket, if I put that thing between the hose housing and the manifold, it will still leak without some other gasket. does that thing mount atop the hose housing?

1 of 1 people found this helpful.

yeah...that's half a gasket....the other half is on the water neck..with a razor blade get it down to metal and get a new gasket or use an evenly distributed bead of RTV black and wait fifteen minutes and put it together... http://www.autopartsnetwork.com/gmc-engine-coolant-thermostat-gasket/av- BNNE



That's not a gasket. It's metal & if you look close, off to the right you see a circuit box that is attached to it. I cleaned off both surfaces. I'm fairly certain there wasn't a gasket on there to begin with, which I thought was kind of interesting. I've never seen that thing before & my shop manual doesn't even mention it but there it is.

1 of 1 people found this helpful.

Don't use a replacement gasket if there was not one on there to begin with. I did and now it's leaking .I snugged the bolts several times and still leaking on the manifold. So now I must drain the radiator [AGAIN!] take gasket off clean and dry it up .This time I'm only using gasket sealer without gasket. I live in Cleveland it was minus 11 degrees when this problem began! I'm certainly not looking forward to doing this again...Don't let the people at the auto parts store sell you something that wasn't on there to begin with.Unless your into doing it twice. I have a 1995 GMC pickup with the same half circle metal sensor gasket and although it was not a hard job I'm not into it[AGAIN!] Cathy from cold ass Cleveland

1 of 1 people found this helpful.

yes..RTV black is an OEM product...used for sealing up differentials~ ford and others use this product....apply a bead...wait fifteen minutes and put them together...your semi-circle sensor will be okay....and sealed too~


Well I decided that thing must have been on top & I just forgot. I got the rubber seal that goes around the thermostat & mounted that thing on top of the neck & it hasn't leaked & it has been running fine. Plus we have heat again. Thanks!

1 of 1 people found this helpful.


I'm having the same issue..but no matter what I do..it shoots water out the front....

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