When was the cooling system flushed last? You could have a blockage, especially in the heater subsystem.
Mine was flushed out this past weekend, and an astounding amount of crap came out. It also solved some weird behaviors, like not enough heat.
Years ago, I had a 1979 Mazda station wagon (a real babe magnet, lemme tell ya’). One winter’s night, I drove it for about an hour in 30 degree (F) weather. The temp needle never moved and heat never came out of the vents. When I got home, the engine was cold to the touch, in spite of having been driven at highway speeds for more than an hour. I don’t think I ever got it fixed and I never noticed the problem again. I have often wondered why having the engine run cold would be such a bad thing.
So today, the check engine light comes on. I take the car in to diagnose it and the guy says that the coolant isn’t getting up to temperature. I explain everything that I’ve told you guys and he wants to check my work. Apparently, I’m an idiot. When I bought the thermostat, they didn’t have a gasket but told me that I could make one with a handy tube of silicone. I did and I checked for leaks and there weren’t any. Unfortunately, the lack of the internal gasket caused the thermostat to be loose within the housing and allowed the coolant to bypass the thermostat. :smack: :smack: :smack:
You’re not an idiot, but the who ever told you to use silicone to make the gasket… may qualify. Next time you need a gasket for your thermostat housing, and the parts guys don’t have one in stock, go to Napa with the housing. They can pretty much match the housing to the right sized gasket in their gasket book with actual sized pics for any application.
Anything that involves a significant amount of pressure should never be relied solely with a silicone made gasket, IMO. Not that this method hasn’t worked for people, but no way am I using just silicone for sealing. Usually the proper made gasket with a light (light) coating of silicone for imperfections in casting, should there be any, usually does the job. Some may disagree, but in my experience, silicone only gaskets, will fail earlier then a properly made gasket for the application. And if it’s a O-ring style gasket, toss the silicone.
Strange. Whenever I have bought a replacement thermostat (not for a long time now though) they have always been supplied together with the apropriate gasket - the fitting instructions always call for a new gasket anyway.