Cleaning Thermostat Housing Surfaces

argus1

Member
Apr 12, 2015
196
Apollo Beach, FL
Boat Info
2011 350 Sundancer
Engines
MerCruiser 377 MAG ECT w/Bravo III Drives, Axius
I am installing a new thermostat. My question is, How clean do the mating surfaces for the thermostat housing need to be? Do I clean the surface on the engine block to be shiny metal. I got the old gasket material off but it looks like it may be still covered with old sealant. I want to make sure that I have a good contact surface for the metal contacts in the new gasket. What is best way to make sure that the surfaces are clean enough without taking a chance of damage. Thanks in advance.
 
+1 for sandpaper and emery cloth.
Big chunks can be taken off with a stiff putty knife.
Stuff a rag in the hole to prevent chunks from entering in the block.
 
+1 for sandpaper and emery cloth.
Big chunks can be taken off with a stiff putty knife.
Stuff a rag in the hole to prevent chunks from entering in the block.

Great advice!
I’ll only add that sometimes you get lucky and they come off in practically one piece if you get under it right with the putty knife or gasket scraper.
If not, just be careful not to gouge the surface trying to clean it.
While you shouldn’t need any sealer on the gasket and it really isn’t necessary, I still like to use an adhesive on the manifold side to line up and hold the gasket down in place while I attach the T stat housing and bolt it down. I usually use Indian Head Gasket Sealer for the job only because that’s what I’ve been using for over 50 years and I usually have it handy in the garage.
 
Great advice!
I’ll only add that sometimes you get lucky and they come off in practically one piece if you get under it right with the putty knife or gasket scraper.
If not, just be careful not to gouge the surface trying to clean it.
While you shouldn’t need any sealer on the gasket and it really isn’t necessary, I still like to use an adhesive on the manifold side to line up and hold the gasket down in place while I attach the T stat housing and bolt it down. I usually use Indian Head Gasket Sealer for the job only because that’s what I’ve been using for over 50 years and I usually have it handy in the garage.
Most of the time on anything that requires old gasket removal I use a razor blade to clean it up.
 
Thanks for the suggestions. One question still remains, "Do I have get the mating surfaces back to shiny metal?"
 
You can use the automotive black silicone gasket maker, easy to use,easy to get apart when time to disassemble, just don't use it for anything with gasoline and you can get it almost any where.
 

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