2000 Chrysler Concorde

The leakage is usually due to not completely cleaning off all of the old gasket. It is also possible to scratch the soft metal with a gasket scraper. Sandpaper works nicely to shine up the engine and the housing. I also like to put a thin film of RTV silicone gasket sealer on both sides of the gasket. It fills in any small scratches and makes the gasket easier to remove next time.

If the thermostat isn't centered properly, it will hold the housing up preventing it from sealing. It's easy then to crack the ears on the housing when you tighten the bolts.

Caradiodoc

I hadn't considered that. I was thinking of the older cast aluminum housings that could crack. You might have a stamped steel housing that can bend instead of cracking.

You have two choices. One is to buy a new housing or find a good one in a salvage yard. The second choice, the one I would try first, is to tap on it with a punch and hammer to try to bend the high spot down, then use gasket sealer on both sides of the gasket. The Chrysler parts department has two really good products. The black stuff stays more flexible and will not form a good seal if there is any oil or transmission fluid residue. The gray sealer gets harder and will seal even if the surfaces aren't perfectly clean. It's a little harder to remove the next time, but not impossible.

The sealer will make the housing just a little harder to remove. You will have to pry the end up which could be what caused this one to get bent in the first place.

Caradiodoc