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Hi everyone. I’ve seen plenty of YouTube videos and comments on this thread, so I think I have the basics of replacing the thermostat. I do have a very specific question, related to the thermostat gasket. I have the original factory service manual
for the 1986 F250, and it specifically says “Coat a new outlet housing gasket with Perfect Seal Sealing Compound…” (see image) So 2 questions:
1) How exactly would you coat the gasket? Should you actually coat the gasket with the sealing compound, or put the sealant compound around the outlet, on both sides, and then just place the gasket on top?
2) I don’t think they sell this compound anymore, but it looks like I may be able to use Permatex Ultra Copper RTV Silicone High Temperature Gasket Maker. Does that sound correct?
I put a very light coat on the metal of what ever I am sealing, then sit the gasket on it. I believe those have a port with a ball in it for venting purposes. Do not block it with your sealer.
I use permatex #2 non hardening sealer. Very light coat on all surfaces to be joined, including both sides of the gasket. This sealer cleans up easy when you have to replace the thermostat. A sharp plastic knife clears surfaces easy enough. I install Motorcraft thermostats, checked in a pot of water for opening temp. But I had one fail open in 6 months. The tstat was covered by the 2 yr warranty. Do test, and good luck.
When checking the t-stat in a pot of hot water it helps to hold the t-stat with tongs to ensure you're testing the water temp. The bottom of the pot could be hotter due to the flame from the stove. I use an instant-read meat thermometer to check water temp.
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