Thermostat and Housing Question

[SEMIJim]

Hi All,

Just last weekend removed the thermostat as part of the winterizing engine flush procedure. Two questions:

1. The thermostat has a coating of rust on it. It's not too bad. Is it safe to give it a soak in CLR, or will it possibly damage/degrade the thermostat?
2. I bought replacement gaskets, but... There's a gasket "stuck" to the top of the engine that appears to be hard rubber in composition and appears to be in good shape. When I took the thermostat out, there appeared to be a silicone type sealant that had been used in addition to that. With just the housing back in place, for the RV anti-freeze flush, there appeared to be no leak. Wondering about the best way to proceed when re-installing the thermostat.

Thanks!

Jim

[Kurt]

I would soak the thermostat in full strength vinegar overnight before trying anything else. I've done this a couple of times and my original OEM thermostat has always come out looking brand new. If there are any rust stains left after soaking, you can also give it a little scrub with a toothbrush. I can't imagine that CLR would damage the thermostat, but I also can't imagine you would need to use that product - vinegar should be all you need.

In terms of winterizing, you have everything back together with no leaks so great. However, when reinstalling the thermostat for regular use next season, I would recommend doing things right and scraping the 'ol rubber gasket you see off as well as 'ol traces of sealant - clean the mating surfaces up. Then just use one of the thermostat gaskets you can get from Moyer or make yourself (I keep like 10 on my boat - they're cheap) and some hi-temp thermostat sealant and you should be good to go. I always have to use permatex sealant on my thermostat housing gasket or it will spray lots of water. That all being said, that hard rubber gasket you see was maybe created by someone before you and, if it looks ok and doesn't appear to be degrading from heat, maybe you can reuse it - just look for leaks as even a dribble over time can give you some nice rust.

[rigspelt]

Then just use one of the thermostat gaskets you can get from Moyer or make yourself (I keep like 10 on my boat - they're cheap) and some hi-temp thermostat sealant and you should be good to go. I always have to use permatex sealant on my thermostat housing gasket or it will spray lots of water.

Is Permatex Aviation Form-A-Gasket "hi temp"?

[Kurt]

There are several different types of Permatex for different applications. I use the one that says it is high temp and formulated for thermostat housing applications. There are other formulations that are more for areas where there is contact with oil. That being said, the form a gasket stuff you are talking about should work.

[rigspelt]

Is Permatex Aviation Form-A-Gasket "hi temp"?

http://www.permatex.com/ "Permatex® Aviation Form-A-Gasket® No. 3 Sealant. Slow-drying, non-hardening brush-top sealant approved for use in aviation as well as automotive applications. Temperature range -65°F to 400°F (-54°C to 204°C); resists gasoline, oil and grease. Suggested Applications: Close-fitting machined surfaces, sealing hoses, solid gaskets."

[SEMIJim]

http://www.permatex.com/ "Permatex® Aviation Form-A-Gasket® No. 3 Sealant. Slow-drying, non-hardening brush-top sealant approved for use in aviation as well as automotive applications. Temperature range -65°F to 400°F (-54°C to 204°C); resists gasoline, oil and grease. Suggested Applications: Close-fitting machined surfaces, sealing hoses, solid gaskets."

I wonder if that's the stuff that was used in the past? Like I said: Whatever was on there, it looked and behaved kind of like clear silicone sealant.

Jim

[rigspelt]

I wonder if that's the stuff that was used in the past? Like I said: Whatever was on there, it looked and behaved kind of like clear silicone sealant.

Permatex Aviation is dark amber.

[SEMIJim]

Permatex Aviation is dark amber.

Ok. Question is: Will Permatex Aviation sealant allow me to remove and replace the thermostat repeatedly w/o destroying the existing gasket (which seems to be in fine condition) and being able to easily remove the previous applications?

Jim

[rigspelt]

Ok. Question is: Will Permatex Aviation sealant allow me to remove and replace the thermostat repeatedly w/o destroying the existing gasket (which seems to be in fine condition) and being able to easily remove the previous applications?Jim

My notes indicate that Don once wrote this in "Instructions for installing gaskets" (which I cannot find online at present): "... The following gaskets should be sealed as indicated. Permatex Aviation brand sealer seems to work well. Except where noted, gaskets should be installed dry (without sealer) including the head gaskets ... (MM-003) Late model thermostat housing gasket - lower side only, so that the housing can be removed for servicing without damaging the gasket later ... (MM-021) Early model Dole thermostat housing - coat one side of gasket only, so that the housing can be separated later for servicing ...". Note that this applied to the gaskets they sold, and might not apply to other gaskets.