Well I'm on try three here and I'm running out of ideas so I turn to you guys for your input. I had a leak at the thermostat housing on my V10 in Feb. Took it off to find the PO had just used a ton of red RTV to seal it, no gasket. After cleaning it all out there appeared to be a grove molded into the bottom of the housing that looks like it may have held a rubber seal or something, but it's empty now, just had a lot of RTV in it. So I bought a regular gasket, used the RTV recommended for water pumps / thermostat housings. Worked for about 5 mins and started leaking bad. Redid it and it held up until about a week ago when I notice coolant leaking again. Redid the gasket and this time filled the grove with RTV and let it set for a few hours before I filled the system. Now it's leaking again.

Being that the housing is plastic I feel like it just warps when you tighten it down. But I don't want to crank it too much and break it, the bolts are already really tight.

So what I am I to do? Can I get a replacement seal that fits in that molded channel in the housing? My only other thought was to fill that channel with something and sand it down to be flush with the rest of the housing and see if I can get the correct pressure that way to stop the leak.

Sorry, this turned out to be much longer than I expected, thanks if you have read this far into it.

 

It looks like there is supposed to be a seal there:
http://www.rockauto.com/catalog/x,ca...,parttype,2182

Here are the directions from the service manual to install the thermostat:
(1) Clean mating areas of intake manifold and thermostat housing.
(2) Check the condition (for tears or cracks) of the rubber thermostat seal located in the intake manifold. The thermostat should fit snugly into the rubber seal.
If seal replacement is necessary, coat the outer (metal) portion of the seal with Mopar® Gasket Maker. Install the seal into the manifold using Special Seal Tool number C-3995-A with handle tool number C-4171.
(3) Install thermostat into recessed machined groove on intake manifold.
(4) Install gasket on intake manifold and over thermostat.
(5) Install housing-to-intake manifold bolts. Tighten bolts to 25 N-m (220 in. lbs.) torque.
CAUTION: Housing bolts should be tightened evenly to prevent damage to housing and to prevent leaks.
(6) Connect the wiring to both sensors.
(7) Install the upper radiator hose and hose clamp to thermostat housing.
(8) Install support rod.
(9) Fill cooling system.
(10) Connect negative battery cable to battery.
(11) Start and warm engine. Check for leaks.

 

That seal shown in the link actually goes in the intake. The plastic housing is the problem. Do a search it's not that uncommon. The newer dodges switched to a aluminum housing at least my 98 is and thats the route I would go. Also when doing the gasket with the aluminum housing skip the rtv and just use some gasket adhesive.

 

Get a seal and a new housing. Should be able to acquire both at the parts store or at least the dealership. Use the gray thermostat rtv and torque it down. Let it cure for at least three hours before you fill it with coolant.

As a general rule for any two point mounting surface, I never apply full torque to one side and then the other, I always do it in a partial sequence, like half torque both sides, then full torque. Probably a good rule to follow regardless of how many anchor points you have on any gasket surface.

 

Thanks guys. No idea why Dodge thought plastic was a good idea. I'll see if I can find a new one and try sealing it that way then. Thanks again for the advice.

 

I have a 96 V10 had the same problem took mine off cleaned it good used a piece of sand paper on a flat surface a made sure the housing was flat, rtv and it fixxed the leak. Hope that will help