Thermostat and gasket

Michael Mattix

SCCoA Member
Ok, so I have to share my first time changing the thermostat and gasket. Well, I'm kind of embarrassed to say, but the gasket has been leaking a little bit since before I can remember. Finally, mostly because of it being a lower priority with kid responsibilities taking precedence, I finally did it. First try, didn't get the right gasket (didn't know it wasn't right at the time) and when I took it apart I found out. Since some on this board have put just rtv on it, I tried that. Next day after set up, it leaked pretty strong. I guess I don't know how to let copper rtv set up. So, second attempt I got a (what I'm going to call) a four hole (not 3 hole...2 bolt holes and one big coolant hole) gasket. Bought two just in case. WISH I would have taken in the mating metal hose. That night after work I tried to get everything all back together. To my dismay, the four hole gasket wasn't the right one and didn't match up hardly. I postponed any attempt to cut it and try and make due, but finding the right one was hard. FORD: "It's going to be hard to find....try KOI". Local parts place where the dealers get some of their parts. They had one that matched up pretty darn close. And I bought water pump type rtv. So, put it on both sides of gasket, and squished it down against the metal pipe and that held in the thermostat (that thing falling out is a nightmare....the idea someone posted about putting a small dot of loctite at the top is great, just make sure your loctite isn't out of date...I think mine was....didn't hold) and after the thermostat fell out a few times and a few explicative's were said and had to clean up where the rtv touched that it wasn't meant to, it's all back together. I put the bolts hand tight and then torqued it properly the next day. Welp, it's not leaking. Wow, I sure hope the next time it's not that hard.
 

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FYI

The Gasket we need for the thermostat housing is carried by Advance Auto Parts.
Fel Pro part #35459

I Buy 2 of everything at the parts store, so when I need it, it's on the shelf at home, not ordered from a parts store with a 3 day wait.

I had the same issue with RTV sealant alone. Glad you got your leak fixed.
 
I ran into the same thing when I replaced mine. I found the one recommended in and earlier at Advance Auto Parts and bought a couple just to have around. They are pretty cheap.
I had problems with the gasket and thermostat dropping out when I went to bolt it in place. After acouple of attemps I used a little gasket sealer to hold the thermostat in place on the motor and let it set-up. I also put some gasket sealer on the housing and let it get tacky. Once it was tacky I applied the gasket to the housing.
Be patient and let things set-up a little before putting it all together. When I finally put it all together I put some gasket sealer on the motor and bolted it all together. I waited to run the motor so all of the sealant could dry. It works great. No problems since. You my want to make sure the housing isn't bent on the side facing the gasket or you will get a leak.
 
One simple trick to keep the thermostat from falling out of the groove on the housing is to put a couple of drops of superglue on it then as mentioned using some rvt on the gasket.
 
Thanks Mike, and yes I think it should be a FAQ with a collaboration of all the tips and tricks. I read all I could (don't remember coming across that post, but thanks) and for those who want to use gaskets, it was weird that most people here I read seemed to use the gasket WITH some rtv. My Helms Ford manual did not say to use anything except the gasket.
 
The use of RTV came about due to the stamped steel nature of the thermostat housing and the use of only two bolts. All it takes is one person to over torque the bolts, and then the housing will become bent and leak. Ongoing over tightening distorts it further. RTV is used to take up the gaps from the distortion.

Best solution if warped is to take some emery paper down on a flat surface (like the garage floor) and run the face of the housing back and forth over the paper until you see even wear across the facing. That will tell you the thing is now flat. Then don't overtighten it when you put it back on.

This type of issue is common enough that automakers and Felpro have a new design gasket that has a raised ridge around the sealing service in a thermoplastic material. This acts as an o-ring and provides a very positive seal. Unfortunately such a gasket is not available in our application last I checked.
 
I just double gasket it. Never had one leak when doing that. The extra $3 is worth the headache to me. Gasket making material is your friend. Take the kids cereal box and make a gasket. Let it be up to him/her to figure out what the hole shape cut out the box was used for.
 
If you have a belt sander you can hold the housing against the belt and flatten it. Works great. I use RTV with a gasket and let it set up for a couple of hours or so so the thermostat doesn't fall out. Don't try to use a 5.0 thermostat gasket. They look the same as ours but are slightly too big and will leak.
 
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